Electronic Circuits and Projects Forum

If you already have this photocell; can you tell us what kind of photocell it is (it could be resitive or generate a voltage?),
could you tell us what it does at the dusk level you want? (if it is just an ORP12 or something then that info will do).

Dawn and dusk times (both about 10 seconds) will one 10s timer be OK or will you want different times for dawn and dusk?.

Will the motor just run for 10 secs or will the direction be different?.
:wink:

I have a Maplin (UK) catalogue here that lists four light dependent resistors - the old standard ORP12 is the most expensive (£1.40), I see one at £0.50 - it claims 120k at 10lux and 5Meg at 0lux.

The choice of LDR is easy - whatever is cheapest! give us the spec if you can find it and a simple 741 op-amp circuit will work as a trip amplifier.

I think that the trip amplifier's output could be inverted by a single transistor and two diodes can steer the direct and inverted outputs via simple RC pulse shapers such that either (both now as positive pulses, one at dawn, one at dusk) will start a 555 timer (or even a 4093B Schmitt NAND timer?). The timer could have a few preset times selected by switches or a variable resistor.

What power is the motor ? a power transistor can switch small loads but a relay could be easier for higher currents.

pm me (button below) with an email address and I can send some circuit sketches...