Collection Schematic

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Saturday, November 8, 2014

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.

Wednesday, October 29, 2014

USB Powered Audio Power Amplifier Circuit Diagram

This is the simple USB Powered Audio Power Amplifier Circuit Diagram. This circuit of multimedia speakers for PCs has single-chip-based design, low-voltage power supply, compatibility with USB power, easy heat-sinking, low cost, high flexibility and wide temperature tolerance. At the heart of the circuit is IC TDA2822M. This IC is, in fact, mono-lithic type in 8-lead mini DIP package. It is intended for use as a dual audio power amplifier in battery-powered sound players. Specifications of TDA2822M are low quiescent current, low crossover distortion, supply voltage down to 1.8 volts and minimum output power of around 450 mW/channel with 4-ohm loudspeaker at 5V DC supply input.

An ideal power amplifier can be simply defined as a circuit that can deliver audio power into external loads without generating significant signal distortion and without consuming excessive quiescent current. This circuit is powered by 5V DC supply available from the USB port of the PC. When power switch S1 is flipped to ‘on’ position, 5V power supply is extended to the circuit and power-indicator red LED1 lights up instantly. Resistor R1 is a current surge limiter and capacitors C1 and C4 act as buffers. Working of the circuit is simple. Audio signals from the PC audio socket/headphone socket are fed to the amplifier circuit through components R2 and C2 (left channel), and R3 and C3 (right channel).

Circuit diagram:

USB

USB Powered Audio Power Amplifier Circuit Diagram

Potmeter VR1 works as the volume controller for left (L) channel and potmeter VR2 works for right (R) channel. Pin 7 of TDA2822M receives the left-channel sound signals and pin 6 receives the right-channel signals through VR1 and VR2, respectively. Ampl i f ied signals for driving the left and right loudspeakers are available at pins 1 and 3 of IC1, respectively. Components R5 and C8, and R6 and C10 form the traditional zobel network. Assemble the circuit on a medium-size, general-purpose PCB and enclose in a suitable cabinet. It is advisable to use a socket for IC TDA2822M. The external connections should be made using suitably screened wires for better result.

Sourced By: EFY

Saturday, September 13, 2014

Self powered Fast Battery Tester

This schema runs a fast battery test without the need of power supply or expensive moving-coil voltmeters. It features two ranges: when SW1 is set as shown in the schema diagram, the device can test 3V to 15V batteries. When SW1 is switched to the other position, only 1.5V cells can be tested.

Battery

Parts:
R1______________2K2 1/4W Resistor R2______________3R3 1/4W Resistor R3_____________10R 1/4W Resistor R4______________4K7 1/4W Resistor R5_____________33K 1/4W Resistor R6,R7_________100K 1/4W Resistors R8____________220K 1/4W Resistor R9____________330K 1/4W Resistor R10___________500K Trimmer Cermet C1,C2__________10nF 63V Polyester Capacitors C3-C7_________100nF 63V Polyester Capacitors C8____________220µF 35V Electrolytic Capacitor D1,D7___________LEDs Red 5mm. (see Notes) D2-D6________1N4148 75V 150mA Diodes Q1___________2N3819 General purpose FET Q2,Q3_________BC337 45V 800mA NPN Transistors IC1,IC2________7555 or TS555CN CMos Timer ICs P1_____________SPST Pushbutton SW1____________DPDT Switch BUT____________Battery under test Holder or clips to connect the Battery under test to the schema Testing 3V to 15V batteries: 1. Switch SW1 as shown in the schema diagram. 2. Place the battery under test in a suitable holder or clip it to the schema. 3. Wait some seconds in order to let C8 reach its full charge. 4. LED D1 illuminates at a constant intensity, independent of battery voltage. 5. If D1 illuminates very weakly or is completely off the battery is unusable. 6. If D1 has a good illumination, press P1 and keep an eye to LED D7. If D7 remains completely off, the battery is in a very good state. 7. If D7 illuminates brightly for a few seconds, the battery is weak. This condition is confirmed by a noticeable weakening in D1 brightness. 8. If D7 illuminates weakly for a few seconds but D1 maintain the same light intensity, the battery is still good but is not new. Testing 1.5V batteries: 1. Switch SW1 in the position opposite to that shown in the schema diagram. 2. Place the battery under test in a suitable holder or clip it to the schema. 3. Wait some seconds in order to let C8 reach its full charge. 4. LED D1 illuminates very weakly only in presence of a new battery, otherwise is off. 5. Press P1 and keep an eye to LED D7. If D7 remains fully off the battery can be in very good state. 6. If D7 illuminates brightly for a few seconds, the battery is weak. 7. If D7 illuminates weakly for a few seconds, the battery is still good but is not new. 8. If you are suspecting a 1.5V cell to be completely discharged, a better test can be made wiring two 1.5V batteries in series, then running the 3V test. Circuit operation: FET Q1 provides a constant current generator biasing LED D1 and Q2 Base. In this manner D1 illuminates at a constant intensity, independent of battery voltage from 3 to 15V and Q2 (when P1 is closed) applies a constant current load of about 120mA to the battery. IC1 is a square wave generator oscillating at about 3KHz. IC2 acts as an inverter and drives, together with IC1 but in anti-phase, Diodes D2-D6 and Capacitors C4-C7, obtaining a voltage multiplication. C8 is charged by this raised voltage and R8-R10 form a voltage divider biasing the Base of Q3. When P1 is open, a very light load is applied to the battery under test and Q3 Base is biased in order to maintain LED D7 in the off state. Closing P1, a 120mA load is applied to the battery under test. If the battery is not fully charged, its output voltage starts reducing: when this voltage falls 0.6V below the battery nominal voltage, Q3 Emitter becomes more negative than the Base, the transistor is hard biased and D7 illuminates. Obviously, this state of affairs will last a few seconds: the time spent by C8 to reduce its initial voltage to the new one, proportional to the voltage of the loaded battery. If the battery under test is in a good charging state, its output voltage will not fall under a 120mA loading current, so LED D7 will stay off. When testing 1.5V batteries, the schema formed by Q1, Q2, D1, R1 & R2 does not work well at this supply voltage, so a 150mA load current is applied to the BUT by means of the 10 Ohm resistor R3 after switching SW1A. Q3 bias is also changed via SW1B. Notes: * To set-up this schema apply a 6 to 7.5V voltage source to the input and trim R10 until LED D7 is completely off (without pushing on P1). * 1.5V test position needs no set-up. * CMos 555 ICs must be used for IC1 & IC2 because they are the only cheap devices able to oscillate at 1.5V supply or less.

Wednesday, August 27, 2014

NiMH NiCd Li ion lead acid Solar Powered Battery Charger

This is the NiMH, NiCd, Li-ion, lead acid Solar Powered Battery Charger Circuit Diagram. solar battery charger that will charge a variety of batteries: NiMH, NiCd, Li-ion, lead acid. Although there are solar battery chargers on the market, most are only for one application: cell phone, NiMH batteries, etc. Our charger will have the user input the battery type, capacity, and voltage. It will display the charge status and incorporate various safety systems, including temperature monitoring and battery polarity checking.

NiMH, NiCd, Li-ion, lead acid Solar Powered Battery Charger

Friday, August 22, 2014

24V DC Powered Beeper with 4 Separate Inputs

24v DC is a very popular voltage used in industrial settings. This hobby schema below was designed to accept four different 24v DC alarm input signals, which are then used to drive a single low power beeper. The beeper is a magnetic type with its own oscillator/driver. The four diodes form an “OR” gate so any one of the four inputs will cause the beeper to make noise. A CMOS version of the popular 555 timer is used to strobe the beeper on and off at about 1Hz.

Source :Streampowers