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dark sensor using a kit

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Dancin David

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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.

**broken link removed**
 
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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
 
hi,

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

If you post the diagram perhaps we could advise.:)
 
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.
 

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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 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 :D

(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 ;))
 

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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)
 
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.
 
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 :)
 
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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.
 
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
 

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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
 
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?
 
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.
 
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.

The dying cow sound, could be the relay buzzing at a high rate.

This shouldnt happen if the +Vfeedback is set correctly.
All that means when the 'dark' switches the unit ON, it should take a little more 'light' to switch it OFF.. like a dead band, else the relay will buzz.

Whats the value of R1 ,2 and 3 and P1.?
 
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He he Eric,
it's getting desperate now :)

It might be driving you crazy David, but you will have learned 10x more, than you would have if it worked first time :)
 
David,
Have you tried adjusting P1?
 
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