Showing posts with label automatic. Show all posts
Showing posts with label automatic. Show all posts
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.
Tuesday, October 28, 2014
Automatic Emergency Lamp Circuit
This is an automatic emergency lamp with day light sensing, means it senses darkness/night and turns ON automatically. Similarly it senses day light and turns OFF automatically. A simple emergency lamp which does not require any special equipment; even a multimeter to assemble and use. Any individual who can do a good quality soldering must be able to build this circuit successfully.
This can be easily accommodated in the defunct two 6 watt tube National Emergency Lamp or any PL tube type emergency lamp. The difference will be in the working; it will work non stop for more than 8 hours. Deep discharge is taken care by the LED characteristic and over charge protection is taken care by the fixed voltage regulator.This uses a simple 3Pin fixed regulator which has a built in current limiting circuit.
Simple Emergency Light Circuit Diagram:
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| Automatic Emergency Lamp Circuit |
The only required adjustment is the preset which has to be set to ensure the LEDs just light up (it should be left at that position). The 5mm LDR is just mounted on top of the emergency light as shown in the photograph. LDR is used to avoid it lighting up during day time or when the room lights are ON. 2 LEDs are used in series; the dropping resistance is avoided and 2 LEDs light up with current that is required for a single LED, by which energy is saved to a great extent.
This particular circuit has been kept so simple for people who has limited access to components or in other words this is an emergency light that you can build with minimum components. In addition to circuit diagram, He has shared photographs of the prototype he made in National emergency light and a PCB design.
Friday, September 26, 2014
150 watt Inverter Circuit with Automatic Battery Charger Changeover Output
Many of the readers have time and again requested for inverter circuits. Given below is one such system, rated at 150 watts, complete in all respects.
The circuit works automatically when mains supply fails and switches back to charging mode when the supply is resumed. A prototype of the same has been constructed by me and is in operation for the last 4% years, power in a 122 cm (4 feet) ceiling fan and a tube light. The circuit shown here may be divided into two sections: The first, charger section, includes step-down transformer Xl to provide l2V—0—l2V AC. When switched on through Sl, relay RLI gets energised by the DC voltage supplied by one set of full-wave rectifier comprising D3 and D4. This rectified DC voltage smoothed by C1 is again brought down to the required RLl coil voltage through R2 and C2. When RL1 gets energised, it connects the mains live line to the output socket through RLl’s N/O contacts. Diodes D1 and D2 form another set of full-wave rectifier which charges the battery through resistor R1 and the N/ C contacts of relay RL2.
The value of Rl should be so chosen as to give the desired current level. lt is advisable to have two or three resistors in parallel, each rated 25W. A 20 ampere meter may be connected between the battery`s negative terminal (after the fuse) and the RL2’s main contact to monitor the charging rate as well as the consumption during inverter operation. When the AC mains supply fails, relay RL1 gets deenergised and connects the live line of the secondary of the inverter transformer X2 to the output socket through its N/ O contacts. At the same time, RLl causes RL2 to operate through its N /C contacts. (lt is assumed that S2 is in on position.) ln this circuit the transistors operate as switches. Resis tors R3 through R6 are used to provide the requisite base drive through the feedback winding for starting the oscillations. , Slight imbalance in the two halves of the primary winding of X2 as well as in the component values, causes one set of transistors to conduct. Say, for example, T1 is conducting while T2 is off thus the supply to the top half of the primary winding through the RL2 contact (Of course it is assumed the mains supply is off and that switch S2 is in ON position) When T1 is in full Conduction, heavy current flows in the transformer which saturates the core causing the magnetic field to collapse as also the polarities of all the windings in X2 to reverse and also the switching positions of the transistors too. Because of the auto-transformer action, a potential of twice the supply voltage is developed across the total primary winding of X2, which is stepped up by the secondary winding. This process continues. R7, C4, D5 and D6 are used to protect the transistors from spikes while C3 and C5 are used to improve the oscillations. Resistors R8 and R9 have been incorporated to facilitate distribution of current equally amongst the transistors. The value of R8 and R9 is around 0.05 ohm each; these can be made by taking about 1.75 metres of 20S WG enamel wire and winding it over a pencil to give it the shape ·of a coil.
Some useful hints regarding the proposed inverter with charger changeover circuit
1. On switch on (S2), if the circuit does not function, reverse the feedback winding connection of one set (or both, if required). In other words, if the beginning of L2 is connected to emitter of Tl , the other end of feedback winding L1 should be connected to the base of T2.
2. Connection from the battery terminals to the chassis tag should be as short as possible, and the wire used must be rated to carry 13 to 14 amperes.
3. Wherever heavy current flows, i.e. from the tag to the RL2 contacts and from there to emitter resistors (R8 and R9) through the centre—tap of X2, wiring must be done by 15SWG wire.
4. The no—load current is 5.5 to 6.5 amperes, depending upon the base drive. For a 122 cm ceiling fan load, it will rise to 8.5 to 9 amperes, and for both fan and tube light it will rise to around 12 to 13 amperes. lf it is more or less, adjust the values of R4 and R5 suitably.
5. Efficiency will be around 80 per cent on full load.
6. Sometimes the tube light may not light immediately on switch on, or it may start blinking when the fan is working. In such an event, a 0.68 F paper condenser rated at 400V in series with a push button switch may be connected (as shown by dotted lines) across A and B terminals of X2. However this is not necessary when it automatically takes over upon failing of mains. provided S2 and tube light switch are kept closed.
A 12V 5 plate lead-acid battery used in automobiles is the minimum requirement for this system. This battery can be used for about four hours continuously at full load. Since the battery is used in inverter system, it never attains full charge, even when put under charge for long hours. As these batteries are not intended for cyclic operation, only 75 per cent of the stored energy can be used. Deep discharge or over-charge should be avoided.
The circuit works automatically when mains supply fails and switches back to charging mode when the supply is resumed. A prototype of the same has been constructed by me and is in operation for the last 4% years, power in a 122 cm (4 feet) ceiling fan and a tube light. The circuit shown here may be divided into two sections: The first, charger section, includes step-down transformer Xl to provide l2V—0—l2V AC. When switched on through Sl, relay RLI gets energised by the DC voltage supplied by one set of full-wave rectifier comprising D3 and D4. This rectified DC voltage smoothed by C1 is again brought down to the required RLl coil voltage through R2 and C2. When RL1 gets energised, it connects the mains live line to the output socket through RLl’s N/O contacts. Diodes D1 and D2 form another set of full-wave rectifier which charges the battery through resistor R1 and the N/ C contacts of relay RL2.
The value of Rl should be so chosen as to give the desired current level. lt is advisable to have two or three resistors in parallel, each rated 25W. A 20 ampere meter may be connected between the battery`s negative terminal (after the fuse) and the RL2’s main contact to monitor the charging rate as well as the consumption during inverter operation. When the AC mains supply fails, relay RL1 gets deenergised and connects the live line of the secondary of the inverter transformer X2 to the output socket through its N/ O contacts. At the same time, RLl causes RL2 to operate through its N /C contacts. (lt is assumed that S2 is in on position.) ln this circuit the transistors operate as switches. Resis tors R3 through R6 are used to provide the requisite base drive through the feedback winding for starting the oscillations. , Slight imbalance in the two halves of the primary winding of X2 as well as in the component values, causes one set of transistors to conduct. Say, for example, T1 is conducting while T2 is off thus the supply to the top half of the primary winding through the RL2 contact (Of course it is assumed the mains supply is off and that switch S2 is in ON position) When T1 is in full Conduction, heavy current flows in the transformer which saturates the core causing the magnetic field to collapse as also the polarities of all the windings in X2 to reverse and also the switching positions of the transistors too. Because of the auto-transformer action, a potential of twice the supply voltage is developed across the total primary winding of X2, which is stepped up by the secondary winding. This process continues. R7, C4, D5 and D6 are used to protect the transistors from spikes while C3 and C5 are used to improve the oscillations. Resistors R8 and R9 have been incorporated to facilitate distribution of current equally amongst the transistors. The value of R8 and R9 is around 0.05 ohm each; these can be made by taking about 1.75 metres of 20S WG enamel wire and winding it over a pencil to give it the shape ·of a coil.
Some useful hints regarding the proposed inverter with charger changeover circuit
1. On switch on (S2), if the circuit does not function, reverse the feedback winding connection of one set (or both, if required). In other words, if the beginning of L2 is connected to emitter of Tl , the other end of feedback winding L1 should be connected to the base of T2.
2. Connection from the battery terminals to the chassis tag should be as short as possible, and the wire used must be rated to carry 13 to 14 amperes.
3. Wherever heavy current flows, i.e. from the tag to the RL2 contacts and from there to emitter resistors (R8 and R9) through the centre—tap of X2, wiring must be done by 15SWG wire.
4. The no—load current is 5.5 to 6.5 amperes, depending upon the base drive. For a 122 cm ceiling fan load, it will rise to 8.5 to 9 amperes, and for both fan and tube light it will rise to around 12 to 13 amperes. lf it is more or less, adjust the values of R4 and R5 suitably.
5. Efficiency will be around 80 per cent on full load.
6. Sometimes the tube light may not light immediately on switch on, or it may start blinking when the fan is working. In such an event, a 0.68 F paper condenser rated at 400V in series with a push button switch may be connected (as shown by dotted lines) across A and B terminals of X2. However this is not necessary when it automatically takes over upon failing of mains. provided S2 and tube light switch are kept closed.
A 12V 5 plate lead-acid battery used in automobiles is the minimum requirement for this system. This battery can be used for about four hours continuously at full load. Since the battery is used in inverter system, it never attains full charge, even when put under charge for long hours. As these batteries are not intended for cyclic operation, only 75 per cent of the stored energy can be used. Deep discharge or over-charge should be avoided.
Friday, September 5, 2014
Automatic Speed Controller for fans Coolers
During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of one’s body decreases. Thus, initially the fan/cooler needs to be run at full speed. As time passes, one has to get up again and again to adjust the speed of the fan or the cooler.The device presented here makes the fan run at full speed for a predetermined time. The speed is decreased to medium after some time, and to slow later on. After a period of about eight hours, the fan/cooler is switched off.Fig. 1 shows the schema diagram of the system. IC1 (555) is used as an astable multivibrator to generate clock pulses. The pulses are fed to decade dividers/counters formed by IC2 and IC3. These ICs act as divide-by-10 and divide-by-9 counters, respectively. The values of capacitor C1 and resistors R1 and R2 are so adjusted that the final output of IC3 goes high after about eight hours.The first two outputs of IC3 (Q0 and Q1) are connected (ORed) via diodes D1 and D2 to the base of transistor T1.
It can be seen that initially the fan shall get AC supply directly, and so it shall run at top speed. When output Q2 becomes high and Q1 becomes low, relay RL1 is turned ‘off’ and relay RL2 is switched ‘on’. The fan gets AC through a resistance and its speed drops to medium. This continues until output Q4 is high. When Q4 goes low and Q5 goes high, relay RL2 is switched ‘off’ and relay RL3 is activated. The fan now runs at low speed.Throughout the process, pin 11 of the IC is low, so T4 is cut off, thus keeping T5 in saturation and RL4 ‘on’. At the end of the cycle, when pin 11 (Q9) becomes high, T4 gets saturated and T5 is cut off. RL4 is switched ‘off’, thus switching ‘off’ the fan/cooler.Using the schema described above, the fan shall run at high speed for a comparatively lesser time when either of Q0 or Q1 output is high. At medium speed, it will run for a moderate time period when any of three outputs Q2 through Q4 is high, while at low speed, it will run for a much longer time period when any of the four outputs Q5 through Q8 is high.If one wishes, one can make the fan run at the three speeds for an equal amount of time by connecting three decimal decoded outputs of IC3 to each of the transistors T1 to T3. One can also get more than three speeds by using an additional relay, transistor, and associated components, and connecting one or more outputs of IC3 to it.
Friday, August 22, 2014
Basic Automatic Day Night Lamp with LDR
Automatic Day-Night Lamp wit LDR
![Basic]()
Maybe it's a lot who know how to work this one series, but I wanted to share back to the beginner on this. In the existing lighting circuit automatic lights that use components LDR (Light Dependence Resistor).
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Maybe it's a lot who know how to work this one series, but I wanted to share back to the beginner on this. In the existing lighting circuit automatic lights that use components LDR (Light Dependence Resistor).
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