Help with Dark activated relay circuit please

[Kadett200is]

Hi everyone

I want to build this circuit:
**broken link removed**

My question is will it work on 12V? Or must I put in a resistor to limit the current to the transistor? I did print documents on how transistors work but didn't get time to read throught it. Transistors still make's me confused. If there is a great tutorial on transistors that I can understand, something like "Transistors for dummies" LOL. can you please post a link.
I would appreciate any help please. I want to build this circuit this weekend to see if it works on the light a want to use it on. During the week it's work work work and no time to play.

 

[ericgibbs]

Hi everyone

I want to build this circuit:
**broken link removed**

My question is will it work on 12V? Or must I put in a resistor to limit the current to the transistor? I did print documents on how transistors work but didn't get time to read throught it. Transistors still make's me confused. If there is a great tutorial on transistors that I can understand, something like "Transistors for dummies" LOL. can you please post a link.
I would appreciate any help please. I want to build this circuit this weekend to see if it works on the light a want to use it on. During the week it's work work work and no time to play.

hi,
You would need a 12V relay and would increase R3 to 2.2K.

Bob Bowman's Free Educational Technologies: Votech Links

 

[Kadett200is]

Thanks for the reply.

 

[ericgibbs]

Thanks for the reply.

hi,
If you are stuck with a 6V relay, if you know the relay coil resistance you could connect a fixed resistor of equal value in series and use it on 12V.

 

[Kadett200is]

Did thought of that but luckilly I have a 12v relay. But to think of it I do have 6v relay's and they are a bit smaller. What is the formula to work out the resistor value when I have the coil's resistance? The 6v relays might work better because they are smaller in size.

 

[Kadett200is]

Oops. read your reply to fast. Must the value just be the same as the coils resistance?

 

[ericgibbs]

Oops. read your reply to fast. Must the value just be the same as the coils resistance?

Yes the same value or close.

 

[Kadett200is]

Thanks alot for your help. Gonna try to build this asap. Thanks