Solar streetlights can be easily integrated with a dusk-dawn controller by simply employing a pnp transistor and a few resistors where the solar panel itself works as the sensor. But what about other lighting sources that do not employ solar panels such as automatic lighting systems in small wind turbines, automatic lighting in cars or battery based systems where automatic lighting is necessary?
A simple, low-cost, yet an effective solution for the dusk-dawn controller circuit is described here.(a) dawn mode, (b) dusk mode and (c) prototype
Circuit and working
Circuit diagram of the dusk-dawn controller is shown in Fig. It is built around a light-dependent resistor (LDR), n-channel MOSFET IRF640 (T1), 12V LED light or a small inverter (100W) and a few other components.
The 12V battery-operated circuit is designed such that the common battery supply is used for operating the circuit as well as for load, that is, for power LED/small inverter circuit. Resistors R1 and R2 are used as a voltage divider and a current limiter in the circuit, respectively. LED is used as circuit de-activation indicator. LDR is the main component for actuation of the dusk-to-dawn sensing. The n-channel MOSFET IRF640 is for the switching action of the LED light or the small inverter connected to the system through switches S1 and S2, respectively.
With daylight falling on LDR , resistance of LDR becomes low, a small current flows through LED and it glows. At the same time, due to low voltage across LDR, MOSFET IRF640 does not trigger. So load remains off.
But when the surrounding area of LDR (dusk mode) is dark (at night), resistance of LDR becomes very high, no current flows through LED and it does not glow. At the same time, due to higher voltage across LDR, IRF640 triggers. So load light comes on, provided switch S1 or S2 is on.
IRF640 can handle a maximum current of approximately 18A, but you can limit its application to approximately 8A-9A only, based on which the heat-sink is attached to the
PCB and component layout
After assembling the circuit, enclose it in a suitable box. The unit should be fixed on the pillar in such a way that the daylight falls directly on LDR.
A simple, low-cost, yet an effective solution for the dusk-dawn controller circuit is described here.(a) dawn mode, (b) dusk mode and (c) prototype
Circuit and working
Circuit diagram of the dusk-dawn controller is shown in Fig. It is built around a light-dependent resistor (LDR), n-channel MOSFET IRF640 (T1), 12V LED light or a small inverter (100W) and a few other components.
The 12V battery-operated circuit is designed such that the common battery supply is used for operating the circuit as well as for load, that is, for power LED/small inverter circuit. Resistors R1 and R2 are used as a voltage divider and a current limiter in the circuit, respectively. LED is used as circuit de-activation indicator. LDR is the main component for actuation of the dusk-to-dawn sensing. The n-channel MOSFET IRF640 is for the switching action of the LED light or the small inverter connected to the system through switches S1 and S2, respectively.
With daylight falling on LDR , resistance of LDR becomes low, a small current flows through LED and it glows. At the same time, due to low voltage across LDR, MOSFET IRF640 does not trigger. So load remains off.
But when the surrounding area of LDR (dusk mode) is dark (at night), resistance of LDR becomes very high, no current flows through LED and it does not glow. At the same time, due to higher voltage across LDR, IRF640 triggers. So load light comes on, provided switch S1 or S2 is on.
IRF640 can handle a maximum current of approximately 18A, but you can limit its application to approximately 8A-9A only, based on which the heat-sink is attached to the
MOSFET.
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