Collection Schematic

Friday, December 12, 2014

Wireless IR headphone receiver schematic

This is example circuit of Wireless IR headphone receiver.A photodiode Dl feeds high gain IR remote control preamp 1C, a CA3237E. U2 is a PLL FM detector tuned to around 100 kHz.

6v 12vdc converter circuit

This inverter circuit can provide up to 800mA of 12V power from a 6V supply.
For example, you could run 12V car accessories in a 6V (British?) car.he circuit is simple, about 75% efficient and quite useful.

By changing just a few components, you can also modify it for different voltages.

Transistor Checker

This simple circuit can check transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter junctions. It can also check the output power transistors on amplifier circuits. Circuit operation is as follows. The 555 timer ( IC1 ) is set up as a 12hz multi vibrator.

The output on pin 3 drives the 4027 flip-flop ( IC2). This flip-flop divides the input frequency by two and delivers complementary voltage outputs to pin 15 and 14.

Thursday, December 11, 2014

D I Y Gold Detector Schematic

Here the very simple and easy build gold detector circuit.The circuit capable to sense gold or metal or coins from a distance of about 20cm, depending on the size of the object to detect.The circuit oscillates at ab out 140kHz and a harmonic of this frequency is detected by an AM radio.You can simply tune the radio receiver until a squeal is detected.

Thursday, November 20, 2014

Troubleshooting STR IC Regulator Power Supply

A. Unable to start.

Can be caused by:

No start-up voltage supply Vcc or a voltage less than 16V
Electrolityc Capacitors supply voltage Vcc filter dry.

2. Led indicator blinking

If the supply voltage Vcc examined rocking. This is because the regulator of life and death because OVLO work., Die-protectionist regulators and auto start life over and over. If it is turned off Electrolityc Capacitors usually still keep the rest of the cargo.

Can be caused by:

Electrolityc Capacitors supply voltage Vcc filter on a pin-4 dry. Replace with a value equal to or slightly larger. - triger UVLO
input filter capacitor on pin-1 feed dry behind the declining value - triger OLP
Rectifier diode of the switching transformer is damaged (sometimes when examined with avo-meter looks like a still good)
cause the supply voltage Vcc drops of the switching transformer (UVLO)
Part damage or broken lines on the feedback circuit of the voltage regulator through B to photocoupler - triger OVP
Electrolityc Capacitors dry filter voltage B - triger OVP
One of the output voltage of the switching transformer secondaries there is a short (over load) - triger OLP
Soft start capacitor value decreases - triger OLP

3. Noise arising (noise)

Can be caused by:

Transformer windings slack.
If there are ceramic capacitors - can sometimes cause interference noise due to its characteristic piezoelectrik like crystal resonator. Replace with film capacitors.

4. When the st-by normal stress. But when the power is on the regulator directly off protectionism no voltage on the secondary this part. Electrolityc Capacitors are still storing charge.

Can be caused by:

Sensor OVP small value resistor on pin-2 to the ground so that the value of delayed triger to OLP or OCP.
Regulator IC is damaged

Excellent Electronics Heterodyne Detector

The bat ultrasounds are best up by the microphone SPKR1 and go through two stages of addition at Q1 and Q2. Separately, a tunable (R12) distinct abundance is produced by the LM567 oscillator U1. The LM567 is a accent decoder but actuality its ascribe is ashore and its voltage controlled oscillator is acclimated as a attention oscillator. The oscillator abundance is accustomed by

 f = 1/(1.1*C4*(R10 + R12))
 = 1/(1.1*0.0022*10^-6*(4.7 + [0-50])*10³)
 = [88-7.5] khz

The two signals are alloyed at Q3 to aftermath both a arresting in the audio ambit and college frequencies that are again filtered out.

The actual audio arresting undergoes a aftermost date of controlled (R13) addition with the LM386 at U2 afore actuality accessible for achievement at AUDIO OUT. The ability antecedent is a simple 9V battery, so this apparatus is absolutely portable.

Wednesday, November 19, 2014

Active Crossover 2 Way Schematics

Therefore this architecture represents the simplest access I could booty and still get the adapted outcome.The band akin audio arresting enters the absorber area it is astern out of phase.This is to atone for the filters which will alter the appearance afresh appropriately abiding the arresting to it’s able phase. The filters are more-or-less accepted low and aerial canyon filters appropriately however, added capacitors and resistors accept been added in adjustment to get the altruism bottomward to a minimum appliance alone E12 components.

This alive Cantankerous over is adequately beeline forward. It consists of a absorber and two 3rd order, 18 dB per octave filters. One low canyon and the added high. The cantankerous over abundance is set at 2Khz and is advised for AEK’s 400watt per access PA/Keyboard Amp systems. Obviously alone one access is apparent here.

This ambit may not be of awfully abundant use to anyone as it was accurately advised to clothing the applications. It is not capricious or switchable for two reasons. Firstly, it didn’t charge to be back the backdrop of the apostle arrangement were already known. And secondly, the added complication was put into the accurateness of the crossover rather than it’s flexibility. The filters are akin in account to anniversary added as able-bodied as can be accepted appliance alone E12 components. If switching were to be active to accord a ambit of abundance options, a accommodation would accept to be fabricated on clarify accuracy.

The alone added way to accomplish a accepted crossover architecture and advance accurateness would apparently be to use Switched capacitor clarify architecture blocks. In theory, two 18or 24dB per octave filters could be complete such that they tracked anniversary added by actuality bound to the aforementioned clock. This would be a nice agreement but I haven’t had the befalling to prove this technology for this affectionate of application. My primary affair was the breach through of switching babble appliance such a design.

Simple Sound to Light Converter Schematic Diagram

Simple Sound-to-Light Converter Schematic Diagram

Figure 1 shows a simple ambit for converting an audio arresting (such as one that comes from the apostle terminals of a CD player). The ambit basically consists of a buffer/amplifier date and three clarify circuits: a high-pass filter, a mid-pass filter, and a low-pass filter. The achievement of anniversary clarify ambit drives a light-emitting diode of altered color.

The ascribe arresting is fed to the absorber date through C1. The ethics of RF and RV1 should be called so that the absorber is able to drive the three filters absorbed to its output. The low-frequency, mid-frequency, and high-frequency apparatus of the ascribe arresting are alone accustomed to canyon through the low-pass clarify (bottom filter), the mid-pass clarify (middle filter), and the high-pass clarify (topmost filter), respectively, appropriately amid them from anniversary other.

Changes in the achievement of a clarify account its agnate achievement LED to about-face on and off. In effect, agriculture a connected audio arresting to the ascribe of this ambit causes the LEDs to dance.

Tube amplifier with power 25 Watt

Tube Power Amplifier 35W Push Pull is made using a tube and eventually compiled configuration push-pull amplifier. Tube Power Amplifier 35W Push Pull tube til it using EL-34 as the amplifier end.

In the power amplifier that is made with a tube at a glance looks simple because the use of active components that are not complex. It should be noted that the use of tubes in Tube Power Amplifier 35W Push Pull require a high voltage supply, therefore in the process of making and finishing must be careful of high voltage and radiation. Detailed series of Tube Power Amplifier 35W Push Pull can be seen in the following figure.

Tube Power Amplifier Series 35W Push Pull

Sign Components Tube Power Amplifier 35W Push Pull
R1 = 470K 0.5 W
R2-5 = 2K2 0.5W
R3 = 150K 0.5W
R4 = 220K 0.5W
R6-10 = 56K 0.5W
R7 = 3.9K 0.5W
R8 = 220R 0.5W
R9 = 1M 0.5W
R11 = 39K 1W
R12-23 = 180K 0.5W
R13-21 = 820K 0.5W
R14-22 = 5K6 0.5W
R15-20 = 680K 0.5W
R16-19 = 100K 0.5W
R17-18 = 3K3 1W
R24 = 470R 2W
TR1-2 = 470R 1W Variable (adj. 270Ω)
C1-3-6-7 = 0.1uf 630V
C2 = 220pF 600v
C4-5 = 16uF 550V
C8-9 = 0.1uF 630V
C10-14 = 0.47uF 630V
C11-13 = 25uF 40V
V1 = E80CC
V2 = E80CC
V3-4 = EL34
Rectifier tube = Z2C
Audio Transformer for T1 = 2x EL34 Push Pull

Power amplifier with tubes often become the choice for a small slewrate so that the resulting audio quality is guaranteed. Tube Power Amplifier 35W in the circuit that is required to supply a high DC voltage is +220 VDC ddengan order to work properly.

FET Touch Switch

The series of touch this switch be an Sklar sentu made using FET. This circuit serves to activate electronic devices only when we touch touch sensors. Once we release a touch to the sensor, the electronic device that is connected is turned off again. The series of touch switch or touch switch is very simple, composed only of a FET, resistor and capacitor. The series of touch switches / touch switches work with source voltage 12VDC. Detailed series of touch switches / touch switch can be seen in thethe following figure .

FET Touch Switch

The series of touch switches / touch switch can only be used to illuminate DC, 12V DC lamp when it replaced the relay, the circuit can be used safely to load the AC network. Sensor touch to this series was made with 2 pieces of plate are arranged close together (within 1-2mm).

Tuesday, November 18, 2014

Low Cost Digital Volume Control Amplifier

TDA8551 Mini Digital Volume Control Amplifier

Amplifier with digital volume control can we create a predictably simple because the article Mini BTL Amplifier with Digital Volume Control This series is made only with 1 IC TDA8551. The series of Mini BTL Amplifier with Digital Volume Control is a power amplifier with BTL type 1Watt. Techniques for adjusting the volume in this series has been provided with a pin point control that is controlled by providing an input voltage VCC and GND. The series of Mini BTL Amplifier with Digital Volume Control selector also features mute, standby and operating.

The series of Mini BTL Amplifier with Digital Volume Control is quite simple and small enough to make an amplifier for room or to headphones. Hopefully useful and can provide ideas for making digital amplifier with volume control.

Water Level Indicator Alarm

This ambit not alone indicates the bulk of baptize present in the aerial catchbasin but additionally gives an anxiety back the catchbasin is full.

The ambit uses the broadly accessible CD4066, mutual about-face CMOS IC to announce the baptize akin through LEDs.

When the baptize is abandoned the affairs in the catchbasin are accessible circuited and the 180K resistors pulls the about-face low appropriately aperture the about-face and LEDs are OFF. As the baptize starts bushing up, aboriginal the wire in the catchbasin affiliated to S1 and the + accumulation are shorted by water. This closes the about-face S1 and turns the LED1 ON. As the baptize continues to ample the tank, the LEDs2 , 3 and 4 ablaze up gradually.

The no. of levels of adumbration can be added to 8 if 2 CD4066 ICs are acclimated in a agnate fashion.

When the baptize is full, the abject of the transistor BC148 is pulled aerial by the baptize and this saturates the transistor, axis the buzzer ON. The SPST about-face has to be opened to about-face the buzzer OFF.

Remember to about-face the about-face ON while pumping baptize contrarily the buzzer will not sound!

Melody Generator using M66T

This is the actual simple way to comedy a song with distinct 1.5 battery. You can body this circuit for allowance acceccories. When the allowance opened, again a song will be played.. It’s accessible and bargain right..? :D . It aloof use a distinct baby dent which will accomplish a song which already buried central the chip.

Components List:
C = 1uF
R = 4.7KW
Q = 2SC9013

About IC M66T series:
The M66T series is a CMOS LSI designed melody generator IC for use in telephones and toys application. It has an on-chip ROM programmed for musical performance. Produced by CMOS technology, the device results in very low power consumption. And with built-in RC oscillator, a compact melody module can be constructed with only a few additional components.

M66T pin assignment:

Pin 1 (O/P) Melody Output
Pin 2 (Vdd) Positive Power Supply
Pin 3 (Vss) Negative Power Supply

The following are the M66T series and the song generated by its series:

M66T-01L : Jingle Bells + Santa Claus Is Coming To Town + We Wish You A Merry Christmas
M66T-05L : Home Sweet Home
M66T-09L : Wedding March (Mendelssohn)
M66T-19L : For Alice
M66T-68L : It Is A Small World

Monday, November 17, 2014

Dual Power Supply Circuits

This is a bench top power supply that can be used to power circuits or devices during development work in the lab. More specifically it is an adjustable, tracking, dual rail supply which means there are two supply voltages, one positive, one negative, that are adjusted by a common potentiometer such that supply voltages are equal in magnitude. It is capable of supplying up to +/- 15V DC at up to 1A. This is sufficient for the majority of small signal electronic projects.

Dual Power Suplly Circuit diagram.

Click to view larger

Power Supply circuit above shows the circuit layout for this project. A centre tapped transformer (TR1) is used with two 12V secondary windings with its centre tap tied to ground. This allows positive and negative voltages to be generated with respect to the central ground. Rectification follows based upon the bridge rectifier (BR1) and smoothing capacitors (C1, C2, C4 and C5).

Two linear regulators are used, an LM317 on the positive side and an LM337 on the negative side. These regulators keep the supply voltage constant for a varying load up to a load current of around 1A. The voltage adjustment is achieved through potentiometers RV1 and RV2 in the positive side of the circuit. The clever part of this circuit comes from the mirroring of the positive voltage adjustment to the negative side via the op-amp U2 to give the circuit its tracking nature.

The op-amp U2 has its positive input tied to ground via a 4K7 resistor. This means that, providing there is negative feedback around the op-amp, the op-amp will endeavour to make its negative input also at ground or 0V. The negative feedback is arranged by the output of the op-amp U2 driving the Adjust pin of the negative regulator U3 and by resistors R3 and R4. The op-amp U2 sets the voltage on the adjust pin of U3 such that the voltage at its negative input is 0V. Also as R3 and R4 are equal, the positive and negative regulated voltages must then be equal in magnitude.

An analogue meter is driven from the positive side to give an indication of the voltage setting. Two switches are used to allow the positive and negative supplies to be turned on/off independently and there are also two LED acting as indicators.

Dual Power Supply Construction

This power supply circuit was built up on Veroboard as it is quite simple to build. Heatsinks can be mounted to the two regulators to improve the current drive capability. The transformer and circuit were mounted inside a wooden box. If a metal box is used the box must be connected to mains earth to prevent a shock hazard. Figure 2 shows a picture of the finished unit. It should be noted that this box is rather shabby and the author has been meaning to improve it for a while but it does do the job nicely.

LM317 Simple Audio Amplifier

You most likely know that LM317 IC is applied as an practical provide regulator, but did you know it can be applied as an audio amplifier? This is a Low power Amplifier LM317 Simple Audio Amplifier Circuit a audio designed with LM317 that offers a optimum probable 1W audio strength.

LM317 Simple Audio Amplifier Circuit Diagrams :

LM317 Simple Audio Amplifier Circuits

Utilization a amazing heatsink for the LM317 IC and modify the 5K various resistor so that you have 4.5V on 10Ω resistor (or LM317 pin 2, Vout).

Audio Peak Indicator

The existence of the peak indicator "Audio Peak Indicator" in an audio device is needed. Audio Peak indicator is a simple circuit to detect the peak level of audio signal. Audio Peak indicator circuit is built with duabuah transistor and LED indicator sebgai peak level detection of audio signals. The main function of a series of Audio Peak indicator is to determine the occurrence of the peak level of audio signal that is more than +4 dB, equivalent to 1.25 V rms. If the received audio signal Audio Peak Indicator more than +4 dB was the LEDs in series Peak Audio This indicator will light. Audio Peak indicator circuit is mounted on the output audio system.

Image Series Audio Peak Indicator

Audio Peak Indicator Component List:
R1 = 10Kohm
R2 = 1.2Kohm
R3 = 220Kohm
R4-5 = 4.7Kohm
C1 = 47uF 25V
C2 = 2.2uF 25V
Q1-2 = BC550C
D1 = LED RED

We hope to form the reference materials in the manufacture of circuit pernagkat Audio Peak Indicators in the audio readers.

Sunday, November 16, 2014

32 768 KHz Oscillator using Watch Crystal

32.768 KHz Oscillator using Watch Crystal

a 32.768 KHz square wave from a common watch crystal. The output can be fed to a 15 stage binary counter to obtain a 1 second square wave. The circuit on the left using the 4069 inverter is recommended over the transistor circuit and produces a better waveform. The single transistor circuit produces more of a ramping waveform but the output swings the full supply voltage range so it will easily drive the input to a CMOS binary counter.

Friday, November 14, 2014

LIGHT TO FREQUENCY CONVERTER CIRCUIT

This is the circuit diagram of a effective light to frequency converter circuit that can be used for variety of applications such as light intensity measurement,fun etc. This circuit is based on TLC555, the CMOS version of famous timer IC NE 555. A photo diode is used for sensing the light intensity. The timer IC is wired in astable mode. The leakage current of the reverse biased photo diode is proportional to the light intensity falling on it. This leakage current charges the capacitance C1. When the capacitor voltage reaches 2/3 of the supply voltage the out put (pin 3) goes low. As a result the capacitor discharges through photo diode .When the capacitor voltage reaches 1/3 the supply voltage the out put (pin 3) of IC goes high. This cycling continues and we get a frequency at pin 3 proportional to the light intensity falling on the photo diode.

Light to Frequency Converter Circuit Diagram & Parts List

Points to remember

With the given components the frequency varies from 1KHZ @ complete darkness to 24 Khz @ bright sunlight.The frequency range can be changed by using different values for C1.
Use any general purpose photo diode for D1.

ANALOG TO DIGITAL CONVERTER A D

This type of converter is used to convert analog voltage to its corresponding digital output. The function of the analog to digital converter is exactly opposite to that of a DIGITAL TO ANALOG CONVERTER. Like a D/A converter, an A/D converter is also specified as 8, 10, 12 or 16 bit. Though there are many types of A/D converters, we will be discussing only about the successive approximation type.

Successive Approximation Type Analog to Digital Converter

A successive approximation A/D converter consists of a comparator, a successive approximation register (SAR), output latches, and a D/A converter. The circuit diagram is shown below.

The main part of the circuit is the 8-bit SAR, whose output is given to an 8-bit D/A converter. The analog output Va of the D/A converter is then compared to an analog signal Vin by the comparator. The output of the comparator is a serial data input to the SAR. Till the digital output (8 bits) of the SAR is equivalent to the analog input Vin, the SAR adjusts itself. The 8-bit latch at the end of conversation holds onto the resultant digital data output.

Working

At the start of a conversion cycle, the SAR is reset by making the start signal (S) high. The MSB of the SAR (Q7) is set as soon as the first transition from LOW to HIGH is introduced. The output is given to the D/A converter which produces an analog equivalent of the MSB and is compared with the analog input Vin.

If comparator output is LOW, D/A output will be greater than Vin and the MSB will be cleared by the SAR. If comparator output is HIGH, D/A output will be less than Vin and the MSB will be set to the next position (Q7 to Q6) by the SAR.

According to the comparator output, the SAR will either keep or reset the Q6 bit. This process goes on until all the bits are tried. After Q0 is tried, the SAR makes the conversion complete (CC) signal HIGH to show that the parallel output lines contain valid data. The CC signal in turn enables the latch, and digital data appear at the output of the latch. As the SAR determines each bit, digital data is also available serially. As shown in the figure above, the CC signal is connected to the start conversion input in order to convert the cycle continuously.

The biggest advantage of such a circuit is its high speed. It may be more complex than an A/D converter, but it offers better resolution.

Ultrasonic Mosquito Repeller Circuit Diagram by CD4017

This is a simple ultrasonic mosquito repeller circuit diagram. The circuit is design on the theory that pests like mosquito can be repelled by ultrasonic frequency around (20KHz-25KHz). This ultrasonic mosquito repeller circuit is based on a single CMOS IC CD4017. C1,R1 & VR1 is used to adjust the output frequency.

Circuit Diagram:

Fig: Ultrasonic mosquito repeller circuit diagram

Thursday, November 13, 2014

Infra red Receiver

This very simple infra-red receiver is intended to form an infra-red remote control system with the simple infra-red transmitter described in this site. The system does not use any kind of coding or decoding, but the carrier of the transmitter is modified in a simple manner to provide a constant switching signal. Since the receive module, IC1, switches from low to high (in the quiescent state, the output is high) when the carrier is received for more than 200 milliseconds, the carrier is transmitted in the form of short pulse trains. This results in a pulse at the output of the receiver that has a duty cycle which is just larger than 12.5%. The carrier frequency used in the system is 36 kHz, so that the output frequency of IC1 is 281.25 Hz.

Circuit diagram:

Infra-Red Receiver Circuit Diagram

This signal is rectified with a time constant that is long enough to ensure good smoothing, so that darlington T1 is open for as long as the received signal lasts. A drawback of this simple system is that it may pick up signals transmitted by another infra-red (RC5) controller. In this case, only the envelopes of the pulse trains would appear at the output of T1. This effect may, of course, be used intentionally. For instance, the receiver may be used to drive an SLB0587 dimmer. Practice has shown that the setting of the SLB0587 is not affected by the RC5 pulses. The receiver draws a current of about 0.5 mA.

Proximity Detector

This proximity detector is constructed using an infrared diode detector. Infrared detector can be used in various equipment such as burglar alarms, touch free proximity switches for turning on a light, and solenoid-controlled valves for operating a water tap. Briefly, the circuit consists of an infrared transmitter and an infra-red receiver (such as Siemens SFH506-38 used in TV sets).

The transmitter part consists of two 555 timers (IC1 and IC2) wired in astable mode, as shown in the figure, for driving an infrared LED. A burst output of 38 kHz, modulated at 100 Hz, is required for the infrared detector to sense the trans mission; hence the setup as shown is required. To save power, the duty cycle of the 38kHz astable multivibrator is maintained at 10 per cent. The receiver part has an infrared detector comprising IC 555 (IC3), wired for operation in monostable mode, followed by pnp transistor T1. Upon reception of infrared signals, the 555 timer (mono) is turned ‘on’ and it re-mains ‘on’ as long as the infrared signals are being received.

Circuit Diagram :

Proximity Detector Circuit Diagram

When no more signals are received, the mono goes ‘off’ after a few seconds (the delay depends on timing resistor-capacitor combination of R7-C5). The de-lay obtained using 470kilo-ohm resistor and 4.7µF capacitor is about 3 seconds. Unlike an ordinary mono, the capacitor in this mono is allowed to charge only when the reception of the signal has stopped, because of the pnp transistor T1 that shorts the charging capacitor as long as the output from IR receiver module is available (active low). This setup can be used to detect proximity of an object moving by. Both transmitter and receiver can be mounted on a single breadboard/PCB, but care should be taken that infrared receiver is behind the infrared LED, so that the problem due to infrared leak-age is obviated.

An object moving nearby actually reflects the infrared rays from the infrared LED. As the infrared receiver has a sensitivity angle of 60o, the IR rays are sensed within this lobe and the mono in the receiver section is triggered. This principle can be used to turn ‘on’ the light, using a relay, when a person comes nearby. The same automatically turns ‘off’ after some time, as the person moves away. The sensitivity depends on the current limiting resistor in series with the infrared LED. It is ob-served that with in circuit resistance of preset VR1 set at 20 ohms, the object at a distance of about 25 cms can be sensed. This circuit can be used for burglar alarms based on beam interruption, with the added advantage that the transmitter and receiver are housed in the same enclosure, avoiding any wiring problems.

Yamaha 175 Wiring Diagram and Electrical System Schematic

The following picture shows the Yamaha 175 Wiring Diagram (CT2 and CT3 model) and Electrical System Schematic. Herein you get detail information regarding the interconnection and wiring between electrical parts and components of the motorcycle such as battery, ground, headlight, taillight, horn, rectifier, brake, flywheel magneto, etc.

Yamaha 175 Wiring Color Code

Daytime charging circuit
Night time charging circuit
Battery (+) circuit
Ground circuit
Front brake stop light
Rear brake stop light
Tail light
Head/meter light
Common circuit
Headlight main circuit
Headlight sub circuit
Horn circuit
Rectifier circuit
Flasher
Flasher light right
Flasher light left

Green
Green/Red
Red
Black
Green/Yellow
Yellow
Blue
Blue
Brown
Yellow
Green
Pink
White
Brown/White
Dark Green
Dark Brown

Wednesday, November 12, 2014

Led light bar scan back and forth led two color circuit with explanation

This circuit is a circuit run on alternating two colors.It uses the 2-color LED with a built-in 3-pin single.This will chase away the glow of each LED until the end.It turns alternating to another color.In any way to the moon on the moon first end, then the LED end of the first LED.Circuit consists of, nand gate ic.Two 10 Counter circuits IC, and IC JK flip flop.

Operation of the circuit is divided into 3 sets.It is a set of signal generators, a set of display and control.Set the signal generator is IC1a,and IC1b number 4011 is a signal generator.The R2, R3, C2 determine the frequency generated.The signal is fed to a set of impressions is the number 4011 IC2 and IC3.The 10 counter circuits to output to the LED, and Is the same, but the work must be performed one at side.

Therefore, the signal from pin 11 of IC 2 and tested for D2 and D3,To pin 3 of IC4.The integrated circuit IC 4 is a JK flip flop is connected to a T flip flop.The signal input pin 3 and pin 1 is the output signal.Which sends a signal to the Reset IC either stop working.IC4 on the anniversary, it will output the first time, in contrast to pin1.IC3 make work, IC2 stopped.
IC2 is controlled by signals from pin 1 of IC4, to IC1c.Prior to control IC2.The IC3 is connected to pins 1 through D1 to the control again.

lm3914 led light based music circuit

led

This is a simple light running circuit by music This circuit is not difficult, is MONO, with a few accessories. Can be connected to the output of a CD or cassette player Time.
Operation of the circuit. Begins to be input via VR. The VR will function fine, signal strength coming. D1 will take disconnected hemisphere plus leaving only the signal hemisphere removed to activation of Q1. Signal is extended through Q1 to pin 5 input of IC1. By C1 forward delay of the IC is not the LED (connected to the output. of IC1) off immediately. The IC IC1 is finished. The act shows the effect of the voltage at IC1 pin 5 of the display by the LED to pins 1-19 of the IC, which is within range. compared to a multiple voltage standard circuits. The circuit can operate effectively. In the R1 that it will determine the current flowing through the LED. To prevent LED damage.
Use should be connected to the input of the circuit. To the speaker terminals, change the value of R3 is 10k and IC1 can choose to display two types Bar (Bar) when the pin 9 and a power source. Dots (Dot) on 9-pin to float to drop.

LM3915 Mini Audio Spectrum Analyzer

The circuit has been designed to create a spectrum analyzer that will provide an analysis of a sound to determine at various frequencies, the volume of sounds that make up the overall sound spectrum.
Circuit Explanation
The device is sensitive enough to determine the sound wave components of frequency and amplitude with the changing of frequency and the width of an acoustic signal. The proportionality of signal width is indicated by the brightness of LED as it turns ON while the color indicates the proportionality of frequency. In order for the red LED to turn ON in strong signal, the sensitivity of the input circuit is adjusted by resistor R2. The middle signal is represented by a yellow LED while the low signal is indicated the green LED.

Audio Spectrum Analyzer

The 10 LEDs in 3 lines comprise the display unit which is ensured the IC2 as it functions as a counter decoder represented by the two gates ICa-b.the frequency of the counter is being regulated by R6. No LED will turn ON in the absence of any signal in the input. The LEDs will begin to flicker or blink depending on the intensity and tempo of the signal, once a signal has been applied in the input. The values of the resistors R4 & R5 can be varied that will be suitable for the desired requirements. Alternatively, this can be done by placing a 1K ohm trimmer in place of R4 & R5 during the initial regulation and adjustment of the values. It can be eventually removed and replaced with permanent resistors as soon as the desired values are achieved. Additional LEDs can be added in connection to IC2 although this circuit does not precisely measure the input signal.
Part List
R1= 1K8Kohm
R2= 100Kohm trimmer
R3= 1Kohm
R4= 100 ohm…..1Kohm
R5= 100 ohm…..1Kohm
R6= 100Kohm trimmer
C1= 100nF 100V
D1….10= RED LED
D11….20= YELLOW LED
D21….30= GREEN LED
IC1= LM3915
IC2= 4017
IC3= 4011
Application
This audio spectrum analyzer is a user interface component capable of making visible the sound pressure for a range of frequencies over time by taking a sample from an audio data stream and an animated visualization during the play is created in real time. It is ideal for any purpose which includes analysis and identification of human speech, ham radio audio reception tuning, analysis of vocal and instrumental music, evaluation and tuning of musical instruments, analysis of bat echolocation sounds, evaluation and calibration of home audio systems, and analysis and identification of biological sounds. Other uses of the audio spectrum analyzer are in distortion analysis, transfer functions, and digital filtering.

Tuesday, November 11, 2014

One second Audible Clock Circuit Schematic

This accurate one-pulse-per-second clock is made with a few common parts and driven from a 50 or 60 Hertz mains supply but with no direct connection to it. A beep or metronome-like click and/or a visible flash, will beat the one-second time and can be useful in many applications in which some sort of time-delay counting in seconds is desirable. The circuit is formed by a CMos 4024 counter/divider chip and 3 diodes, arranged to divide the frequency of the input signal at pin #1 by 50 (or 60, see Notes).

The input impedance at pin #1 is very hight, so simply touching the pin (or a short track or piece of wire connected to it) is usually enough to provide the necessary input signal. Another way to provide an input signal consists in a piece of wire wrapped several times around any convenient mains cable or transformer. No other connection is necessary.

Circuit diagram:

One second Audible Clock Circuit Diagram

Parts:

R1 = 10K
R2 = 47.K
R3 = 100R
C1 = 1nF-63V
C2 = 10µF-25V
C3 = 100nF-63V
D1 = 1N4148
D2 = 1N4148
D3 = 1N4148
D4 = LED-(Optional, any shape and color, see Notes)
D5 = 1N4148-75V 150mA Diode (Optional, see Notes)
Q1 = BC337-45V 800mA NPN Transistor
IC1 = 4024-7 stage ripple counter IC
BZ1 = Piezo sounder (incorporating 3KHz oscillator)
SPKR = 8 Ohm, 40 - 50mm diameter Loudspeaker (Optional, see Notes)
SW1 = SPST Toggle or Slide Switch (Optional, see Notes)
B1 = 3 to 12V Battery (See Notes)

Notes:

To allow precise circuit operation in places where the mains supply frequency is rated at 60Hz, the circuit must be modified as follows: disconnect the Cathode of D1 from pin #11 of IC1 and connect it to pin #9. Add a further 1N4148 diode, connecting its Anode to R1 and the Cathode to pin #6 of IC1: thats all!

The circuit will work fine with battery voltages in the 3 -12V range.

The visual display, formed by D4 and R3 is optional. Please note that R3 value shown in the Parts list is suited to low battery voltages. If 9V or higher voltages are used, change its value to 1K.

If a metronome-like click is needed, R2 and BZ1 must be omitted and substituted by the circuit shown enclosed in dashed lines, right-side of the diagram.

Stand-by current drawing is negligible, so SW1 can be omitted.

Battery Juicer

More and more electronic devices are portable and run off batteries. It is no surprise, then, that so many flat batteries find their way into the bin and often far too early. When a set of batteries can no longer run some device for example, a flashgun the cells are not necessarily completely discharged. If you put an apparently unserviceable AA-size cell into a radio-controlled clock with an LCD display it will run for months if not years.

Of course not every partially discharged cell can be put in a clock. The circuit presented here lets you squeeze the last Watt-second out of your batteries, providing a bright ‘night light’ - for free! The circuit features a TBA820M, a cheap audio power amplifier capable of operating from a very low supply voltage. Here it is connected as an astable multivibrator running at a frequency of around 13 kHz. Together with the two diodes and electrolytic capacitor this forms a DC-DC converter which can almost double the voltage from between four and eight series-connected AA-, C- or D-size cells, or from a PP3-style battery.

Circuit diagram:

Battery Juicer Circuit Diagram

The DC-DC converter is followed by a constant current source which drives the LED. This protects the expensive white LED: the voltages obtained from old batteries can vary considerably. With the use of the DC-DC converter and 20 mA constant current source a much greater range of usable input voltages is achieved, particularly helpful at the lower end of the range when old batteries are used. With the constant current source on its own the white LED would not be adequately bright when run from low voltages.

An additional feature is the ‘automatic eye’. The LDR detects when the normal room lighting is switched on or when the room is lit by sunlight: its resistance decreases. This reduces the UBE of the transistor below 0.7 V, the BC337 turns off and deactivates the LED. This prolongs further the life of the old batteries. A further LDR across capacitor C reduces the quiescent current of the circuit to just 4mA (at 4V). Light from the white LED must of course not fall on the LDR, or the current saving function will not work.

Sunday, November 9, 2014

Simple Universal PIC Programmer

This simple programmer will accept any device thats supported by software (eg, IC-Prog 1.05 by Bonny Gijzen at www.ic-prog.com). The circuit is based in part on the ISP header described in the SILICON CHIP "PIC Testbed" project but also features an external programming voltage supply for laptops and for other situations where the voltage present on the RS232 port is insufficient. This is done using 3-terminal regulators REG1 & REG2. The PIC to be programmed can be mounted on a protoboard. This makes complex socket wiring to support multiple devices unnecessary. 16F84A, 12C509, 16C765 and other devices have all been used successfully with this device.

Circuit diagram: Simple

Simple Universal PIC Programmer Circuit Diagram

Saturday, November 8, 2014

PIC Controlled Relay Driver

This circuit is a relay driver that is based on a PIC16F84A microcontroller. The board includes four relays so this lets us to control four distinct electrical devices. The controlled device may be a heater, a lamp, a computer or a motor. To use this board in the industrial area, the supply part is designed more attentively. To minimize the effects of the ac line noises, a 1:1 line filter transformer is used.

The transformer is a 220V to 12V, 50Hz and 3.6VA PCB type transformer. The model seen in the photo is HRDiemen E3814056. Since it is encapsulated, the transformer is isolated from the external effects. A 250V 400mA glass fuse is used to protect the circuit from damage due to excessive current. A high power device which is connected to the same line may form unwanted high amplitude signals while turning on and off. To bypass this signal effects, a variable resistor (varistor) which has a 20mm diameter is paralelly connected to the input.

Another protective component on the AC line is the line filter. It minimizes the noise of the line too. The connection type determines the common or differential mode filtering. The last components in the filtering part are the unpolarized 100nF 630V capacitors. When the frequency increases, the capacitive reactance (Xc) of the capacitor decreases so it has a important role in reducing the high frequency noise effects. To increase the performance, one is connected to the input and the other one is connected to the output of the filtering part.

After the filtering part, a 1A bridge diode is connected to make a full wave rectification. A 2200 uF capacitor then stabilizes the rectified signal. The PIC controller schematic is given in the project file. It contains PIC16F84A microcontroller, NPN transistors, and SPDT type relays. When a relay is energised, it draws about 40mA. As it is seen on the schematic, the relays are connected to the RB0-RB3 pins of the PIC via BC141 transistors. When the transistor gets cut off, a reverse EMF may occur and the transistor may be defected. To overcome this unwanted situation, 1N4007 diodes are connected between the supply and the transistor collectors. There are a few number of resistors in the circuit. They are all radially mounted. Example C and HEX code files are included in the project file. It energizes the next relay after every five seconds.

The components are listed below.
1 x PIC16F84A Microcontroller
1 x 220V/12V 3.6VA (or 3.2VA) PCB Type Transformer (EI 38/13.6)
1 x Line Filter (2x10mH 1:1 Transformer)
4 x 12V Relay (SPDT Type)
4 x BC141 NPN Transistor
5 x 2 Terminal PCB Terminal Block
4 x 1N4007 Diode
1 x 250V Varistor (20mm Diameter)
1 x PCB Fuse Holder
1 x 400mA Fuse
2 x 100nF/630V Unpolarized Capacitor
1 x 220uF/25V Electrolytic Capacitor
1 x 47uF/16V Electrolytic Capacitor
1 x 10uF/16V Electrolytic Capacitor
2 x 330nF/63V Unpolarized Capacitor
1 x 100nF/63V Unpolarized Capacitor
1 x 4MHz Crystal Oscillator
2 x 22pF Capacitor
1 x 18 Pin 2 Way IC Socket
4 x 820 Ohm 1/4W Resistor
1 x 1K 1/4W Resistor
1 x 4.7K 1/4W Resistor
1 x 7805 Voltage Regulator (TO220)
1 x 7812 Voltage Regulator (TO220)
1 x 1A Bridge Diode

DC Motor Control Circuit Notes

Here, S1 and S2 are normally open , push to close, press button switches. The diodes can be
red or green and are there only to indicate direction. You may need to alter the TIP31 transistors
depending on the motor being used. Remember, running under load draws more current. This
circuit was built to operate a small motor used for opening and closing a pair of curtains. As an
advantage over automatic closing and opening systems, you have control of how much, or how
little light to let into a room. The four diodes surriunding the motor, are back EMF diodes. They
are chosen to suit the motor. For a 12V motor drawing 1amp under load, I use 1N4001 diodes.

Solar Powered SLA Battery Maintenance

This circuit was designed to ‘baby-sit’ SLA (sealed lead-acid or ‘gel’) batteries using freely available solar power. SLA batteries suffer from relatively high internal energy loss which is not normally a problem until you go on holidays and disconnect them from their trickle current charger. In some cases, the absence of trickle charging current may cause SLA batteries to go completely flat within a few weeks. The circuit shown here is intended to prevent this from happening. Two 3-volt solar panels, each shunted by a diode to bypass them when no electricity is generated, power a MAX762 step-up voltage converter IC.

Circuit diagram:

Solar Powered SLA Battery Maintenance Circuit Diagram

The ‘762 is the 15-volt-out version of the perhaps more familiar MAX761 (12 V out) and is used here to boost 6 V to 15 V.C1 and C2 are decoupling capacitors that suppress high and low frequency spurious components produced by the switch-mode regulator IC. Using Schottky diode D3, energy is stored in inductor L1 in the form of a magnetic field. When pin 7 of IC1 is open-circuited by the internal switching signal, the stored energy is diverted to the 15-volt output of the circuit. The V+ (sense) input of the MAX762, pin 8, is used to maintain the output voltage at 15 V. C4 and C5 serve to keep the ripple on the output voltage as small as possible. R1, LED D4 and pushbutton S1 allow you to check the presence of the 15-V output voltage.

D5 and D6 reduce the 15-volts to about 13.6 V which is a frequently quoted nominal standby trickle charging voltage for SLA batteries. This corresponds well with the IC’s maximum, internally limited, output current of about 120 mA. The value of inductor L1 is not critical — 22 µH or 47 µH will also work fine. The coil has to be rated at 1 A though in view of the peak current through it. The switching frequency is about 300 kHz. A suggestion for a practical coil is type M from the WEPD series supplied by Würth (www.we-online.com). Remarkably, Würth supply one-off inductors to individual customers. At the time of writing, it was possible, under certain conditions, to obtain samples, or order small quantities, of the MAX762 IC through the Maxim website at www.maxim-ic.com.

Friday, November 7, 2014

Playback Amplifier For Cassette Deck

For some time now, there have been a number of tape cassette decks available at low prices from mail order businesses and electronics retailers. Such decks do not contain any electronics, of course. It is not easy to build a recording amplifier and the fairly complex magnetic biasing circuits, but a playback amplifier is not too difficult as the present one shows. The stereo circuits in the diagram, in conjunction with a suitable deck, form a good-quality cassette player. The distortion and frequency range (up to 23 kHz) are up to good standards. Moreover, the circuit can be built on a small board for incorporation with the deck in a suitable enclosure. Both terminals of coupling capacitor C1 are at ground potential when the amplifier is switched on.

Circuit diagram:

Because of the symmetrical ±12 V supply lines, the capacitor will not be charged. If a single supply is used, the initial surge when the capacitor is being charged causes a loud click in the loudspeaker and, worse, magnetizes the tape. The playback head provides an audio signal at a level of 200–500 mV. The two amplifiers raise this to line level, not linearly, but in accordance with the RIAA equalization characteristic for tape recorders. Broadly speaking, this characteristic divides the frequency range into three bands:

Up to 50 Hz, corresponding to a time constant of 3.18 ms, the signal is highly and linearly amplified.
Between 50 Hz and 1.326 kHz, corresponding to a time constant of 120 µs, for normal tape, or 2.274 kHz, corresponding to a time constant of 70 µs, for chromium dioxide tape, the signal is amplified at a steadily decreasing rate.
Above 1.326 kHz or 2.274 kHz, as the case may be, the signal is slightly and linearly amplified. This characteristic is determined entirely by A1 (A1’). To make the amplifier suitable for use with chromium dioxide tape, add a double-pole switch (for stereo) to connect a 2.2 kΩ resistor in parallel with R3 (R3’). The output of A1 (A1’) is applied to a passive high-pass rumble filter, C3-R5 (C3’-R5’) with a very low cut-off frequency of 7 Hz. The components of this filter have exactly the same value as the input filter, C1-R1 (C1’-R1’). The second stage, A2 (A2’) amplifies the signal ´100, that is, to line level (1V r.m.s.).

6Volt Doorbell Light Circuit

This 6V battery operated doorbell light circuit can be affiliated in alongside with any absolute AC230V doorbell. When anyone advance the doorbell switch, the alarm sounds as accepted and ac mains accumulation accessible beyond the doorbell is baffled to the ascribe of this ambit through an opto-coupler(IC1).

Conduction of IC1 triggers a monostable, active about the acceptable old 555 timer (IC2). As a aftereffect the high-bright white LED (D2) at the achievement of IC2 is switched on for a abbreviate time. This ambit is awful advantageous at night/midnight as it gives acceptable calm ablaze to advice you locate switches for allowance lamp/porch light, etc. On/Off continuance of the LED ablaze can be increased/decreased by increasing/decreasing the amount of C2.

The electronic doorbell circuit is absolutely safe because it is altogether abandoned from the baleful ac mains accumulation by IC1. However, accumulate to abstain adventitious contacts with the foreground end of the circuit, which is anon affiliated to the ac supply. Use of a acceptable and acceptable ABS asylum is recommended for this doorbell ablaze unit.

9 Volt 2 Ampere DC Power Supply Circuit Diagram

There is little to be said about this circuit. All the work is done by the regulator. The 7809 can deliver up to 2 amps continuous output whilst maintaining a low noise and very well regulated supply. The circuit will work without the extra components, but for reverse polarity protection a 1N5400 diode (D1) is provided at the input, extra smoothing being provided by C1. The output stage includes C2 for extra filtering, if powering a logic circuit than a 100nF (C3) capacitor is also desirable to remove any high frequency switching noise.Circuit diagram:

Parts:C1 = 100uF-25V electrolytic capacitor, at least 25V voltage rating
C2 = 10uF-25V electrolytic capacitor, at least 6-16V voltage rating
C3 = 100nF-63V ceramic or polyester capacitor
IC = 7809 Positive Voltage Regulator IC
D1 = 1N5400 Diode

Thursday, November 6, 2014

Simple 12V to 220V 100W Transistor Inverter Diagram

This is a simple Simple 12V to 220V 100W Transistor Inverter Diagram. This circuit is an electronic circuit, and use very popular. Build this Simple 12V to 220V 100W Transistor Inverter Diagram and feel free.

Simple 12V to 220V 100W Transistor Inverter Diagram

Converter Circuit 240V AC TO 5VDC POWER SUPPLY used 7805 Regulator

This is simple way to power some 5v logic from a 240v ac source. If a 120v ac power adapter is used, the circuit will also work for 120v ac power lines.

3V Sweeping Siren Alarm

A while back I was challenged by a visitor to the website. He needed a very loud sweeping siren type audio sound generator powered by 3v. He tried some of the commercial sirens but they were not very loud when powered by 3v. He also said that those devices demanded much higher current than he wanted to use. I gave this problem some thought and came up with a design below.
The circuit uses a LTC1799 precision frequency generator from Linear Technology. A 74HC14 hex Schmitt trigger from Texas Instruments is also used to perform several other functions. One section is wired as a simple 7Hz square wave oscillator. The triangle waveform across that capacitor generates the low frequency sweeping signal for the siren. Two resistors bias the LTC1799 for a center frequency of about 2KHz. A flyback DC to DC converter circuit, produces a 40v peak signal, which is turned on and off according to the output of the LTC1799.
The output is connected to a quality piezoelectric beeper, which has a resonant frequency of about 2.5KHz. The result is a siren which is quite loud but draws only 40ma from a 3v supply. A piezoelectric device from Kobitone, part number 254-PB515-ROX, (Mouser part number 245-PB516) shown above works well. If you want something much smaller, although not quite as loud, try the Murata PKM17EPP-2002-BO shown above (Digikey part number 490-4688).Click on Schematic below to view PDF version of this Circuit

3v-SweepingSiren

Wednesday, November 5, 2014

Automatic TV Lighting Switch

The author is the happy owner of a television set with built-in Ambilight lighting in the living room. Unfortunately, the television set in the bedroom lacks this feature. To make up for this, the author attached a small lamp to the wall to provide background lighting, This makes watching television a good deal more enjoyable, but it ’s not the ideal solution. Although the TV set can be switched off with the remote control, you still have to get out of bed to switch off the lamp.

Automatic TV Lighting Switch Circuit diagram:

Consequently, the author devised this automatic lighting switch that switches the background light on and off along with the T V set. The entire circuit is fitted in series with the mains cable of the TV set, so there’s no need to tinker with the set. It works as follows: R1 senses the current drawn by the TV set. It has a maximum value of 50 mA in standby mode, rising to around 500 m A when the set is operating. The voltage across R1 is limited by D5 during negative half- cycles and by D1– D4 during positive half-cycles. T he voltage across these four diodes charges capacitor C1 via D6 during positive half-cycles. This voltage drives the internal LED of solid-state switch TRI1 via R2, which causes the internal triac to conduct and pass the mains voltage to the lamp. Diode D7 is not absolutely necessary, but it is recommended because the LED in the solid-state switch is not especially robust and cannot handle reverse polarisation. Fuse F1 protects the solid-state switch against overloads. T he value of use d here (10 Ω) for resistor R1 works nicely with an 82-cm (32 inch) LCD screen.

With smaller sets having lower power consumption, the value of R1 can be increased to 22 or 33 Ω, in which case you should use a 3-watt type. Avoid using an excessively high resistance, as otherwise TRI1 will switch on when the TV set is in standby mode. Some TV sets have a half-wave rectifier in the power supply, which places an unbalanced load on the AC power outlet. If the set only draws current on negative half-cycles, the cir-cuit won’t work properly. In countries with reversible AC power plugs you can correct the problem by simply reversing the plug. Compared with normal triacs, optically cou-pled solid-state relays have poor resistance to high switch-on currents (inrush currents).

For this reason, you should be careful with older-model TV sets with picture tubes (due to demagnetisation circuits). If the relay fails, it usually fails shorted, with the result that the TV background light remains on all the time. If you build this circuit on a piece of perf-board, you must remove all the copper next to conductors and components carrying mains voltage. Use PCB terminal blocks with a spacing of 7.5 mm. This way the separation between the connections on the solder side will also be 3 mm. If you fit the entire arrangement as a Class II device, all parts of the circuit at mains potential must have a separation of at least 6 mm from any metal enclosure or electrically conductive exterior parts that can be touched.

10 Band Equalizer

The equalizer presented in this article is suitable for use with hi-fi installations, public-address systems. mixers and electronic musical instruments. The relay contacts at the inputs and outputs, in conjunction with S2, enable the desired channel to be selected. The input may be linked directly to the output, if wanted. The input impedance and amplification of the equalizer are set with S1 and S3. The audio frequency spectrum of 31 Hz to 16 kHz is divided into ten bands. Ten bands require ten filters, of which nine are passive and one active. The passive filters are identical in design and differ only in the value of the relevant inductors and capacitors. The requisite characteristics of the filters are achieved by series and parallel networks.

The filter for the lowest frequency band is an active one to avoid a very large value of inductance. It is based in a traditional manner on op amp A1. The inductors used in the passive filters are readily available small chokes. The filter based on L1 and L2 operates at about the lowest frequency (62 Hz) that can be achieved with standard, passive components. The Q(uality) factor of the filters can, in principle, be raised slightly by increasing the value of R19 and R23, as well as that of P1–P10, but that would be at the expense of the noise level of op amp IC1. With component values as specified, the control range is about ±11 dB, which in most case will be fine. A much larger range is not attainable without major redesign.

10-Band Equalizer Circuit diagram:

The input level can be adjusted with P1, which may be necessary for adjusting the balance between the channels or when a loudness control is used in the output amplifiers. Several types of op amp can be used:in the prototype, IC1 is an LT1007, and IC2, an OP275. Other suitable types for IC1 are OP27 or NE5534; and for IC2, AD712, LM833 and NE5532. If an NE5534 is used for IC1, C2 is needed; in all other cases, not. The circuit needs to be powered by a regulated, symmetrical 15 V supply. It draws a current of not more than about 10mA.

Motorcycle Battery Monitor

A circuit for monitoring the status of the battery and generator is undoubtedly a good idea for motorcyclists, as for other motorists. However, not every biker is willing to drill the necessary holes in the cockpit for the usual LED lamps, or to screw on an analogue accessory instrument. The circuit shown here manages to do its job with a single 5-mm LED, which can indicate a total of six different conditions of the onboard electrical system. This is done using a dual LED that can be operated in pulsed or continuous mode (even in daylight). Built on a small piece of prototyping board and fitted in a mini-enclosure, the complete circuit can be tucked inside the headlamp housing or hidden underneath the tank.

Motorcycle Battery Monitor Circuit Diagram:
BatteryCircuit_Diagram01

The heart of the circuit is IC2, a dual comparator. The comparator circuit is built without using any feedback resistors, with the indication being stabilised by capacitors C4 and C5 instead of hysteresis. Small 10-µF tantalum capacitors work well here; 220-µF ‘standard’ electrolytic capacitors are only necessary with poorly regulated generators. Voltage regulator IC1 provides the reference voltage for IC2 via voltage divider R2/R3. The onboard voltage is compared with the reference voltage via voltage dividers R4 /R5 and R6/R7, which are connected to the inverting and non-inverting comparator sections, respectively.

Using separate dividers allows the threshold levels to be easily modiﬁed by adjusting the values of the lower resistors. IC2a drives the anode of the red diode of LED D4 via pull-up resistor R10. The anode of the green diode is driven by IC2b and R11. T2 pulls R11 to ground, thereby diverting the operating current of the green diode of the LED, if the voltage of the electrical system exceeds a threshold level of 15 V (provided by Zener diode D3). The paralleled gate outputs on pins 10 and 11 of IC3 perform a similar task. However, these gates have internal current limiting, so they can only divert a portion of the current from the red diode of the LED.

The amount of current diverted depends on the battery voltage. The two gates are driven by an oscillator built around IC3a, which is enabled via voltage divider R14/R15 and transistor T1 when the battery voltage is sufficiently high. Depending on the state of IC3a, the red diode of the LED blinks or pulses.

The circuit is connected to the electrical system via fuse F1 and a low-pass ﬁlter formed by L1 and C1. If you cannot obtain a low-resistance choke, a 1-Ω resistor can be used instead. In this case, the values of C3, C4 and C5 should be increased some-what, in order to help stabilise the indication. D1 protects the circuit against negative voltage spikes, as well as offering protection against reverse-polarity connection. Due to its low current consumption (less than 30 mA), the circuit could be connected directly to the battery, but it is better to power it from the switched positive voltage.

Pc Temperature Alarm

If your PC overheats, it could damage its expensive components. Here’s a circuit that warns you of your PC getting heated. Today’s computers contain most of the circuitry on just a few chips and reduced power consumption is a byproduct of this LSI and VSLI approach. Some PCs still have power supplies that are capable of supplying around 200W, but few PCs actually consume power to this extent.

On the other hand, apart from some portable and small desktop computers that use the latest micro-power components, most PCs still consume significant amount of power and generate certain amount of heat. The temperature inside the aver-age PC starts to rise well above the ambient temperature soon after it is switched on. Some of the larger integrated circuits become quite hot and if the temperature inside the PC rises too high, these devices may not be able to dissipate heat fast enough. This, in turn, could lead to failure of devices and eventually of the PC. Various means to combat overheating are available, ranging from simple temperature alarms to devices like temperature-activated fans to keep the microprocessor cool.

Here is a temperature alarm that activates an audio ‘beeper’ if the temperature inside the PC exceeds a preset threshold. This temperature is user-adjustable and can be anywhere between 0°C and 100°C. The unit is in the form of a small PC expansion card, which you simply need to plug into any avail-able slot of the host PC. It is powered from the PC and consumes only about 12 mA. The sensor (LM35) used here pro-vides a substantial amount of on-chip signal conditioning, including amplification, level shifting and phase in-version. As a result, it provides an out-put of 10 mV per degree centigrade rise in temperature. It caters to a temperature measurement range of 0°C to 100°C, which corresponds to 0V to 1V of voltage.

Pc Temperature Alarm Circuit Diagram

The voltage-detector stage com-pares the output voltage of the temperature sensor with the preset reference voltage. The output of the comparator goes high if the output potential from the sensor exceeds the reference voltage. When this happens, the voltage comparator enables a low-frequency oscillator, which, in turn, activates the audio oscillator. The out-put of the audio oscillator is connected to a loudspeaker (LS1), which sounds a simple ‘beep-beep’ alarm. The reference voltage determines the temperature at which the alarm is activated.

Fig. 1 shows the circuit of the PC temperature alarm and Fig. 2 shows the pin configuration of sensor LM35. IC LM35 (IC1) is an easy-to-use temperature sensor. It is basically a three-terminal device (two supply leads plus the output) that operates over a wide supply range of 4 to 20V. It consumes only 56 µA at 5V and generates insignificant heat.

IC2 is an operational amplifier used here as a voltage comparator. VR1 pro- vides a reference voltage that can be set anywhere from 0V to approximately 1V, which matches the output voltage range of IC1. This reference voltage is applied to the inverting in- put of IC2 and the output of IC1 is coupled to the non-inverting input. Consequently, the output of IC2 is low if the output of IC1 is below the reference voltage, or high if the output of IC1 exceeds the reference voltage.

Pin details of LM35

Pin

The low-frequency oscillator IC3 is a standard 555 astable multivibrator circuit. It is gated via the reset input at pin 4, which holds output pin 3 low when IC3 is gated ‘off’ (when the out-put of IC2 is low). This prevents IC4 from oscillating. IC4 is another 555 astable multivibrator circuit, gated via its reset input. It has an operating frequency of approximately 2.5 kHz. When IC3 is activated, its output pro-vides a square wave of 1 Hz. This is used to trigger IC4, which gives an audio output of 2.5 kHz in bursts. It is connected to loudspeaker LS1 to generate alarm.

The alarm circuit can be fitted into any spare expansion slot of the PC, but be careful to fit it the right way round. Before setting VR1 to a suitable thresh-old temperature, decide what that temperature should be. The technical specification in your computer’s manual might be of help here. If we assume that the room temperature will not normally exceed 25oC, the temperature of the interior of the computer would be up to 35oC. Unless you have good reason to use a different threshold temperature, VR1 should be set for a wiper potential of 350 mV.

Trial-and-error method can be used in the absence of test equipment to enable VR1, but it would be a bit time-consuming. There is a slight complication in that the computer’s outer casing must be at least partially removed to provide access to VR1. Once VR1 has been adjusted, the outer casing must be put back into place so that the interior of the computer can warm up in the normal way. You must therefore al-low time for the temperature inside the computer to rise back to its nor-mal operating level each time VR1 is readjusted.