Showing posts with label photo. Show all posts
Showing posts with label photo. Show all posts
Monday, October 20, 2014
Photo Electric Street Light Circuit Diagram
This is basically a Schmitt Trigger circuit which receives input from a cadmium sulfide photo cell and controls a relay that can be used to switch off and on a street lamp at dawn and dusk. I have built the circuit with a 120 ohm/12 volt relay and monitored performance using a lamp dimmer, but did not connect the relay to an outside light.
The photo cell should be shielded from the lamp to prevent feedback and is usually mounted above the light on top of a reflector and pointed upward at the sky so the lamp light does not strike the photo cell and switch off the lamp.
Photo Electric Street Light Circuit Diagram
The photo cell should be shielded from the lamp to prevent feedback and is usually mounted above the light on top of a reflector and pointed upward at the sky so the lamp light does not strike the photo cell and switch off the lamp.
Photo Electric Street Light Circuit Diagram
The photo cell is wired in series with a potentiometer so the voltage at the junction (and base of transistor) can be adjusted to about half the supply, at the desired ambient light level. The two PNP transistors are connected with a common emitter resistor for positive feedback so as one transistor turns on, the other will turn off, and visa versa. Under dark conditions, the photo cell resistance will be higher than the potentiometer producing a voltage at Q1 that is higher than the base voltage at Q2 which causes Q2 to conduct and activate the relay.
The switching points are about 8 volts and 4 volts using the resistor values shown but could be brought closer together by using a lower value for the 7.5K resistor. 3.3K would move the levels to about 3.5 and 5.5 for a range of 2 volts instead of 4 so the relay turns on and off closer to the same ambient light level. The potentiometer would need to be readjusted so that the voltage is around 4.5 at the desired ambient condition. Link
The switching points are about 8 volts and 4 volts using the resistor values shown but could be brought closer together by using a lower value for the 7.5K resistor. 3.3K would move the levels to about 3.5 and 5.5 for a range of 2 volts instead of 4 so the relay turns on and off closer to the same ambient light level. The potentiometer would need to be readjusted so that the voltage is around 4.5 at the desired ambient condition. Link
Sunday, January 12, 2014
Photo Transistor Detector
All of the circuits on the PCB are configured so with the intention of as the photosensors are dark, the output of the 556 timers want stay peak. The issue delay period of each one 556 timer can be tainted by selecting as it should be combination ideals representing the R7/C2, R8/C3, R9/C4 and R10/C5 pairs.The LM339 input detection voltage levels for the circuit while publicized is settle on on 1/2 of the supply voltage. If a subordinate before elevated detection level voltage is wanted, the standards of resistors R5 and R6 can be there misused to suit.hint as soon as power is functional to the circuit, the outputs of the 556 timers pray be piercing in place of 1 discharge delay period phase. (Until the timing capacitors hold charged to 2/3rds of the supply voltage.) in attendance are RESET inputs for apiece LM556.
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| Photo Transistor Detector |
These inputs complete not have terminal stop contacts but do have pads with holes to solder wires to if considered necessary. The RESET inputs might take place used to force the outputs of the 556 timers LOW until the timing capacitors have fully charged behind power is practical to the circuit but an outer timer would be required to accomplish this.This circuit does not require a regulated power supply and can carry on on supply voltages of up to 15 volts.
on behalf of in turn on other light detector circuits, comprehend Light Activated Detector Circuits by the side of this put.For added broad in a row on Voltage Comparators see the Voltage Comparator in sequence piece of paper by the side of this place.on behalf of further universal in sequence on LM556 timers see the 555 Timer Information bleep next to this place.threatening - If the polarity of the power supply for this circuit is reversed before the circuit is connected to an AC or else DCC source this circuit pray exist damaged. The most supply voltage meant for this circuit is 15 Volts.
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