dark sensor using a kit - Electronic Circuits Projects Diagrams Free

Dancin David · 25th July 2008, 03:01 PM

Its late, I cant think straight, please help...

after several failed attempts to build a simple LDR circuit to turn on series of LED's at night, I gave up and spent 10 bucks on a KEMO 12v light barrier kit, which can be used as a twilight sensor - I built it, no worries. The only problem is now I have a cute little board that I don't know how to use or how connect my LED's to it.

There is a '+' and a '-' on the kit's board for what I assume is where my battery will go into, but the only 2 little holes in the PCB other then that are near the Relay labeled 'S' and 'P' - Is that where my bank of LED's goes (+-)?

The LED circuit that I built is simply a 120 Ohms resister for 3 super-bright LED's (I will eventually have more of these to get 18 LEDs in total) - that works fine on its own with 12V's, I figured it would be easy enough to put this Kemo twilight sensor in between the battery and the LED's and Abra-Kadabra the lights come on at night)

Im very new to this any help would be greatly appreciated.

jimmythefool · 25th July 2008, 04:22 PM

Pretty much how you said david. The relay contacts are just a switch, controlled by your sensor. Its normally good practice to switch the positive side, so put your positive to 1 contact, the Led chain to the other, and the negative back to your battery. (obvously the led chain has to be the right way round, but you already know this)
regards
Jim

ericgibbs · 25th July 2008, 04:22 PM

hi,

Do you have a circuit diagram for that kit [the photo].?

If you post the diagram perhaps we could advise.

audioguru · 25th July 2008, 04:51 PM

Kemo has the schematic on their website but not the parts list.
The instructions show a single photo-transistor connected in only one of the two positions in the schematic.

Hero999 · 25th July 2008, 06:31 PM

It's pretty obvious, the IC is a generic op-amp like the 741, the resistor values can be calculated pretty easilly.

+ and - are fairly self-explanatory.

Just connect the load in series with the relay contacts.

What colour are the LEDs?

Dancin David · 26th July 2008, 01:13 AM

I attached the circuit diagram of the kit as well as my LED series.

Hero, You said just connect the load in series with the relay contacts, do you mean use the S and P as + and - on my LED series?

Also, Jimmy - with what you said - its sounds like I should not put the + and - from the battery straight to the + and - on the kit, is that right ?

Could some scribble on my .jpg where to put what contacts? Im the kind of guy who reads magazines for the pictures if you know what I mean

(thanks to you all for getting back to me, Im sure we'll get this figured out soon - well you guys probably already do have it figured out

)

Roff · 26th July 2008, 01:36 AM

Do it like this,

Dancin David · 26th July 2008, 02:09 AM

Ok, cool, thanks Roff.

So I give the kit power via the obvious + and - as well as connecting the LED's positive direct to the power supply, but the LEDs negative goes through the switch?

(thanks)

ericgibbs · 26th July 2008, 07:59 AM

Quote:

Originally Posted by Dancin David

Ok, cool, thanks Roff.

So I give the kit power via the obvious + and - as well as connecting the LED's positive direct to the power supply, but the LEDs negative goes through the switch?

(thanks)

Hi David,
The LED -V going to the relay contact is OK, its being switched to 0V anyway.

You could also add a simple manual switch in parallel with the relay contact, giving you a manual 'ON' control.

jimmythefool · 26th July 2008, 09:46 AM

David, it doesnt really matter which side you put the relay on that kind of circuit.Its just like a switch, it could be anywhere, as long as it is in series, and makes/breaks the circuit when activated. It's just a habit I had drummed into me as an apprentice. It applies more to higher voltages where the voltage needs to be isolated as close to the source as possible for safety reasons.
Roff's diagram will work fine..
Good luck

Dancin David · 26th July 2008, 09:58 AM

The only thing about Roffs Diagram that confuses me is that originally 'P' does not appear to be connected but now it is... Im not sure where to put that connection.

so far Im thinking it goes battery(+) and (-) to kit(+) and (-) then kit(S) to led(-) then led(+) to battery(+)

Do I leave that 'P' thing with nothing ?

(incidentally, what does S and P stand for ?)

Thanks in advance.

ericgibbs · 26th July 2008, 10:25 AM

Quote:

Originally Posted by Dancin David

The only thing about Roffs Diagram that confuses me is that originally 'P' does not appear to be connected but now it is... Im not sure where to put that connection.

so far Im thinking it goes battery(+) and (-) to kit(+) and (-) then kit(S) to led(-) then led(+) to battery(+)

Do I leave that 'P' thing with nothing ?

(incidentally, what does S and P stand for ?)

Thanks in advance.

hi,
Added the wires to your dwg.
The +V LED connection could be either side of the diode, I would connect it to the cathode [bar] of the diode.

The P and S are just arbitary names, could be Pole and Switch

Dancin David · 26th July 2008, 11:03 AM

Thanks Eric... but no go...

all hooked up and I get nothing ... WAIT !!!!!

For some reason - it did not work for a few seconds !!!!! but just as I moved my hand to the keyboard and shaded the sensor the LEDs came on !!!!

ITS ALIVE !!!! HAHA!!!! MY MONSTER IS ALIVE!!!!!! MUAHAAAHHAAAAAA

Dancin David · 26th July 2008, 11:31 AM

And... back to being disappointed again... not sure if its a loose connection somewhere or what... but its stops working sometimes for no apparent reason - and when it stops working the relay makes a soft little moaning noise... like a dying baby cow - Is that supposed to happen?

Hero999 · 26th July 2008, 12:11 PM

It sounds like there's a loose connection in the power supply to the kit.

Another thing could be that there isn't enough hysteresis - the value of R1 might need to be lower.

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25th July 2008, 03:01 PM	(permalink)
Dancin David	dark sensor using a kit Its late, I cant think straight, please help... after several failed attempts to build a simple LDR circuit to turn on series of LED's at night, I gave up and spent 10 bucks on a KEMO 12v light barrier kit, which can be used as a twilight sensor - I built it, no worries. The only problem is now I have a cute little board that I don't know how to use or how connect my LED's to it. There is a '+' and a '-' on the kit's board for what I assume is where my battery will go into, but the only 2 little holes in the PCB other then that are near the Relay labeled 'S' and 'P' - Is that where my bank of LED's goes (+-)? The LED circuit that I built is simply a 120 Ohms resister for 3 super-bright LED's (I will eventually have more of these to get 18 LEDs in total) - that works fine on its own with 12V's, I figured it would be easy enough to put this Kemo twilight sensor in between the battery and the LED's and Abra-Kadabra the lights come on at night) Im very new to this any help would be greatly appreciated. Last edited by Dancin David; 25th July 2008 at 03:36 PM. Reason: adding a picture

25th July 2008, 04:22 PM	(permalink)
jimmythefool	Pretty much how you said david. The relay contacts are just a switch, controlled by your sensor. Its normally good practice to switch the positive side, so put your positive to 1 contact, the Led chain to the other, and the negative back to your battery. (obvously the led chain has to be the right way round, but you already know this) regards Jim

25th July 2008, 04:22 PM	(permalink)
ericgibbs	hi, Do you have a circuit diagram for that kit [the photo].? If you post the diagram perhaps we could advise. __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/

25th July 2008, 06:31 PM	(permalink)
Hero999	It's pretty obvious, the IC is a generic op-amp like the 741, the resistor values can be calculated pretty easilly. + and - are fairly self-explanatory. Just connect the load in series with the relay contacts. What colour are the LEDs? __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

26th July 2008, 02:09 AM	(permalink)
Dancin David	Ok, cool, thanks Roff. So I give the kit power via the obvious + and - as well as connecting the LED's positive direct to the power supply, but the LEDs negative goes through the switch? (thanks)

26th July 2008, 09:46 AM	(permalink)
jimmythefool	David, it doesnt really matter which side you put the relay on that kind of circuit.Its just like a switch, it could be anywhere, as long as it is in series, and makes/breaks the circuit when activated. It's just a habit I had drummed into me as an apprentice. It applies more to higher voltages where the voltage needs to be isolated as close to the source as possible for safety reasons. Roff's diagram will work fine.. Good luck Last edited by jimmythefool; 26th July 2008 at 09:47 AM.

26th July 2008, 09:58 AM	(permalink)
Dancin David	The only thing about Roffs Diagram that confuses me is that originally 'P' does not appear to be connected but now it is... Im not sure where to put that connection. so far Im thinking it goes battery(+) and (-) to kit(+) and (-) then kit(S) to led(-) then led(+) to battery(+) Do I leave that 'P' thing with nothing ? (incidentally, what does S and P stand for ?) Thanks in advance.

26th July 2008, 11:03 AM	(permalink)
Dancin David	Thanks Eric... but no go... all hooked up and I get nothing ... WAIT !!!!! For some reason - it did not work for a few seconds !!!!! but just as I moved my hand to the keyboard and shaded the sensor the LEDs came on !!!! ITS ALIVE !!!! HAHA!!!! MY MONSTER IS ALIVE!!!!!! MUAHAAAHHAAAAAA

26th July 2008, 11:31 AM	(permalink)
Dancin David	And... back to being disappointed again... not sure if its a loose connection somewhere or what... but its stops working sometimes for no apparent reason - and when it stops working the relay makes a soft little moaning noise... like a dying baby cow - Is that supposed to happen?

26th July 2008, 12:11 PM	(permalink)
Hero999	It sounds like there's a loose connection in the power supply to the kit. Another thing could be that there isn't enough hysteresis - the value of R1 might need to be lower. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.