Electrical question

I have a light out back of my house on a detached garage that lights up the parking area. I would like to run it off of a mechanical timer so it goes on at 5 p.m. and off at 10 p.m. I would also like to put a photocell on the light so that if it isn't dark at 5 p.m. the light won't come on. Now, I would also like to put a motion detector on the light so that after 10 p.m. when the timer shuts off the light will come back on in case I get home after 10 or someone trying to get in my garage would set it off.
If I feed the light from two different sources (same circuit) one through the timer and photocell and one through the motion detector, would I achieve my goal? Will there be a problem with each source backfeeding through the other. I can't imagine the mechanical timer will be bothered by the load side being hot but I'm not so sure about the photocell or the motion detector. Could I (should I) put diodes in to keep them from backfeeding each other? I won't be putting more than a 100-watt bulb in the fixture.
Thanks for any help, Dave
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You do NOT want to feed through two sources. You need to have a switchable relay to switch from one downfeed circuit to another with the motion sensor. The motion sensor will also have a photocell. so you want to switch to that at 10:)) PM to 5:00 PM

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Edwin Pawlowski wrote:

Thanks for the reply. Can you educate me? What problems am I creating? I can feed the relay through two sources? I don't suppose you could point me to a relay on line that would work? I don't suppose they make a double pole timer switch that would complete one circuit while disconnecting the other and vice versa?
Thanks again, Dave
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alternative plan: take a look at the seasonal lighting department for outdoor photocell with selectable dial for desired hours such as used for christmas lighting. separately pick out that motion light with photocell. that way with 2 bulbs you won't go crazy when one of the control units goes crazy. and with them burning out separately you're less likely to wind up in the dark.
those diodes block AC and pass DC, not what you're looking to do on this.
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I believe you are making the circuit too complicated. The power from the motion detector would override the photocell/timeclock and your light would work off of your motion sensor.
I would recommend just using the motion sensor. Most motion sensors already include a photocell, so your light wouldn't turn on in the daylight.
By using just the motion sensor, you will save money on your electricity bill, because the light would only be on when it detected motion and not for the 5 hour period each night. You would save more money from not having to purchase a timeclock (approx. $50.00) and another photocell (approx. $15.00). The circuit will also be less complicated and have less things to go wrong.
Good luck and be safe,
Wayne www.gilchrist-electric.com
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On 25 Nov 2005 08:55:35 -0800, "gilchrist-electric"

Use the timer to drive the little windmill in the front yard, and that will set off the motion detector....
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I believe you are making the circuit too complicated. The power from the motion detector would override the photocell/timeclock and your light would work off of your motion sensor.
I would recommend just using the motion sensor. Most motion sensors already include a photocell, so your light wouldn't turn on in the daylight.
By using just the motion sensor, you will save money on your electricity bill, because the light would only be on when it detected motion and not for the 5 hour period each night. You would save more money from not having to purchase a timeclock (approx. $50.00) and another photocell (approx. $15.00). The circuit will also be less complicated and have less things to go wrong.
Good luck and be safe,
Wayne www.gilchrist-electric.com
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Nothing wrong with your circuit at all, except as Wayne said, it's unnecessarily complicated

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RBM wrote:

having the light on a few hours each evening. Kind of a "We'll leave a light on for ya" up until 10 p.m. not a "Who goes there?" light that comes on when it catches someone approaching. Complicated yes, but unnecessarily complicated, maybe. Would it work to achieve my goal of having the light on a few hours then just on when someone/something trips it.
Thanks, Dave
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Yes it would!!!

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Check out the ready made motion detector/photocell units available at places like HD. They have ones that are sold seperately from the lights and include a photocell and motion detector all in one unit. They can be set to give you 2/4/6 hours of illumination after sunset and during that time you can have the lights on at 1/4 power if you want. During the time they are at 1/4 power, or after they go out, they will come on at full power if motion is detected. You can also set how long you want them to stay on when motion is detected.
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snipped-for-privacy@optonline.net wrote:

detectors but I didn't know they would give you 2/4/6 hours of illumination after sunset and then switch to motion detecting. I'll go take a look.
Thanks, Dave
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Dave Miller wrote:

Too much work. Check out www.smarthome.com or other supplies and find one fixture that will do it all for you. Don't limit yourself to mechanical timers, they tend to be less reliable anyway.
--
Joseph Meehan

Dia duit
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It seems to be it would be a lot easier and cheaper to install 2 lights. You can buy one with a motion detector at home depot for about 10 to 15 dollars. Put that on one corner of the garage covering the areayou need covered. The other regular light you could just hook up to a timer. Adjust the timer as needed for the season....5pm winter...8 pm summer.
Just my thoughts Pat
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My head is spinning. I think you can keep the light off using a timer but to have two different ways (timer and motion) seems "interesting". You may need to do two lights.
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