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ageniusforhire
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Need a Light Sensor to Turn ON Power

11/09/2015 11:28 AM

Hi everyone. I am looking for a photosensor to turn ON power when it senses light. All the ones i can find turn power off when light contacts them. This is needed to turn on the autofeed for the wood chip burner i have built to heat my home this winter. It will need to turn on 12v dc power. Not sure how many amps, around ten amps i guess. The screw feeding my chip burner is powered by 2 kids "powerwheels" gear motors. Any help finding a sensor like this, or even the correct thing to call it would be helpfull. thank you!

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PWSlack
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#1

Re: need a light sensor to turn ON power

11/09/2015 11:36 AM

The turn off sensor could still be used, however it wouldn't be fail-safe. The interposing device is a relay, with a coil rated for the voltage applied to the sensor, and an appropriate contact rating for the 12V supply and the rated current. Turn on the light, and the relay switches off, closing the contact on the 12V.

Don't forget to put a "flywheel diode" rated to the same current as the load reverse-biased across the 12VDC load, as it will protect the contacts.

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dj95401
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#3
In reply to #1

Re: need a light sensor to turn ON power

11/09/2015 1:21 PM

GA PW, one other-thing the latching coil should also be rated for continuous energized. as far fail-safe as a cheap way of adding redundancy, they could stack 2 N/C relays in series, powered by either the same photo cell or a separate photo cell

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#2

Re: need a light sensor to turn ON power

11/09/2015 12:48 PM

What is your source of light?

AS PWSlack has commented a relay can be used.

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ageniusforhire
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#8
In reply to #2

Re: need a light sensor to turn ON power

11/10/2015 2:27 AM

either an led bulb or the garage light, which is usually left on.

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ozzb
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#11
In reply to #8

Re: need a light sensor to turn ON power

11/10/2015 7:14 AM

If you have to turn the light on to get it to run. Why not just use a switch to turn it on?

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ageniusforhire
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#16
In reply to #11

Re: need a light sensor to turn ON power

12/01/2015 2:27 AM

it is an autofeeder for a wood chip burner, having to turn it on and off negates the AUTO of the whole project. everyone has fires they have to babysit and tent to to stay warm. therefore, i want one that requires minimal babysitting.

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Andy Germany
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#18
In reply to #16

Re: need a light sensor to turn ON power

12/01/2015 7:30 AM

My favourite source for heating!!

Mine is totally automated, all I need to do is fill it occasionally and clean the grate once a week......

Why do you need anything more?

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#13
In reply to #8

Re: need a light sensor to turn ON power

11/10/2015 8:19 AM

You could connect a relay directly to the light source(s) maybe?

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dj95401
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#14
In reply to #8

Re: need a light sensor to turn ON power

11/10/2015 3:07 PM

Your OP-- " I am looking for a photo-sensor to turn ON power when it senses light. And your reply commit #9-- "either an led bulb or the garage light, which is usually left on." - I'm curious, what's the purpose of the photo cell if it's exposed to a light source that's continuously on?

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lyn
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#4

Re: Need a Light Sensor to Turn ON Power

11/09/2015 1:55 PM

Products & Suppliers is the place to go at the top of the page. They do purchasing.
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andreapg
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#5

Re: Need a Light Sensor to Turn ON Power

11/09/2015 8:51 PM

This is a circuit I made two years ago. It works with a power supply of 12Vdc and uses a relay.

http://andreapg.altervista.org/sensore-crepuscolare.jpg

I tried to upload the image here, but it doesn't work
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ageniusforhire
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#9
In reply to #5

Re: Need a Light Sensor to Turn ON Power

11/10/2015 2:35 AM

i never learned how to make circuits or read them very well. i usually just scavenge parts from other things premade,lol. thanks tho. Now if you still have one of those laying around and would sell it low enough, i may well be able to use it.

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andreapg
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#12
In reply to #9

Re: Need a Light Sensor to Turn ON Power

11/10/2015 7:33 AM

I made it on a breadboard just for hobby purpose.
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Andy Germany
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#10
In reply to #5

Re: Need a Light Sensor to Turn ON Power

11/10/2015 3:55 AM

Looks good, but the OP (as far as I am aware) hasn't stated as to whether he wants to buy something built, or to build it himself (the best way I feel as you do!).

The DIY approach is cheap and easily tailored to "fit"!

I was searching, for him, just such a circuit, you were first!!

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Legolaz
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#6

Re: Need a Light Sensor to Turn ON Power

11/09/2015 9:46 PM

This should do just fine. Interface it.

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ageniusforhire
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#7

Re: need a light sensor to turn ON power

11/10/2015 2:26 AM

I may try that one. looks cheap enough if i let the magic smoke out of it,lol. thanks.

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jt
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#15

Re: Need a Light Sensor to Turn ON Power

11/10/2015 7:23 PM

Buy a small solar panel or scavenge one. 12v are quiet common.

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ageniusforhire
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#17

Re: Need a Light Sensor to Turn ON Power

12/01/2015 2:35 AM

ok, i scrapped the light sensor idea for a relay. Thanks for all the good help tho, i may use one of those circuits in the future . i just used a dpst relay switch, and set it up like the "tilt" mechanism on a pinball machine, for those old enough to know what that is,lol.

now it just " tilts"' and shuts off the autofeed when the chip hopper is full. this is on a thermal mass rocket stove, that has been built to burn woodchips, instead of sticks and such. I have now had over 15 hour continuous burns, without having to babysit the darn thing, or clean out the ashes

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Andy Germany
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#19
In reply to #17

Re: Need a Light Sensor to Turn ON Power

12/01/2015 7:31 AM

Or the ash hopper is full?

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Users who posted comments:

ageniusforhire (5); andreapg (2); Andy Germany (3); dj95401 (2); jt (1); Legolaz (1); lyn (1); ozzb (2); PWSlack (1); Tom_Consulting (1)

Previous in Forum: Seeking Recommendations for a Microphone Amplifier   Next in Forum: A Spectrometer for Your Cell Phone

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