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can i add a dusk to dawn senser to a 9 led light ? Answered

I have a diy 9 led marker light,Each led with 100 ohm resistors.
ontop of my wind generator. Powered by 5 - 1.2 v AA (6v) batteries charged by
9v-120 mA 1.0w mini solar panel.
can i add a dusk to dawn circuit/senser/photo cell or somthing to be off at day/on at night ?
The simpler, the better for my little electronic knowledge.
Thank you!


Quercus austrina

Best Answer 8 years ago

Go to your favorite search engine and plug in " dark activated switch schematic " (no quotes) and you'll find quite a few to choose from. In the Google search I did, the link to the Evilmadscientist looks to be the most promising for your setup. You will probably have to play with the value of the resistor (increase) in order to make it work correctly/not draw too much current with your 6 volt setup. As a safe starting point, I'd  place a 10k ohm potentiometer ("pot") in where the 1k ohm resistor is located, connecting only one end of the "pot" to the battery (positive rail in the schematic) and the wiper (center tab) of the pot to the phototransistor collector. Vary the resistance from the full 10k ohm to the lower end, testing to see what maximum value is reliable. When you find it, disconnect the battery and measure the resistance between the 2 connected tabs and use the closest standard value. If it is between 2 standard values, use the lower one in order to assure correct operation.

Good luck!


While you're at it, add up the current draw of your LED's. If the draw is close to 200 mA, you should change the 2n3904 for a beefier one, either a 2n2222 or a 2n4401, 800 mA and 600 mA respectively. If you change the transistor, you'll have to do the testing of the resistor (as above) with the new transistor to ensure proper operation.


felixthecat3Quercus austrina

Answer 8 years ago

will do !
waiting for parts at the moment.
defiantly will check draw from the 8 led's ,and will go from there


8 years ago

If you have very little knowledge of circuits, something you might be able to do is to rewire a 12 hour christmas light timer to work with your setup. It wouldn't go exactly dusk to dawn, but it would probably be the easiest way. The more complicated path would be to wire in a LSD (light sensing diode) like the little yard lights use to turn on and off.


8 years ago

I wou,d think so - It is just a light activated switch - HOWEVER telling you how would require an intimate knowledge of the device in question. that;s up to you.