5th November 2002 09:39 PM
needing help designing circuit.....
I am trying to build a circuit on a timmer and I am not sure on how to do it. I know what I want it to do.. I have a 12vDC source and with a photo cell. At daylight I want a 12V motor to run for 10 or so seconds and an hour before dark I want it to run for another 10 or so seconds.. Not sure on how to build what I'm wanting. Thanks for any help that I can get!!!!
6th November 2002 03:26 PM
More info wanted
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?.
8th November 2002 05:05 AM
No, I dont have the photo cell yet, what would be the best kind to use?? This is how I would like for this to work... At daylight the photo cell will activate a 6VDC or 12VDC motor to run for ten seconds, now if I can use a DIP switch to have different configurations of cycle times for like in between 5 and 20 seconds that would be great too, but no more than 20 seconds.. and sometime before dark, when the photocell acivates agian the DC motor would run for the set amout of time.... I really don't have to use a photocell for this, I just thought that it would be the easiest and cheapest way. If I could use a clock to trigger the this that way I could have more than just two times that the motor would be activated.. I know that there is alot of diffrent ways to build this configurtion, but I would like to build one myself for less than $25 I can get this already made for that price... I hope that I am explaining myself well enough... If you have anyother questions just ask.........Thanks
8th November 2002 12:45 PM
First Idea - Dusk & Dawn switch
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...
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