Activate LED when circuit broken.

A

ApplePiePod

New Member

• Jul 30, 2009

• #1

I wish to create a circuit. (How original)

Basically, when a phototransistor is not making the circuit (No light) I wish to have the circuit light a LED.

Simple.

I can't figure the 'if NOT made, light LED' bit.

 

marcbarker

New Member

• Jul 30, 2009

• #2

I like your screen name apple-pie-pod

You'll not get anything simpler than this:
**broken link removed**

Note to Electronics course Professors, Tutors, Examiners: We're not really helping your Students to cheat, honest!

 

Last edited: Jul 30, 2009

birdman0_o

Active Member

• Jul 30, 2009

• #3

Here's a good link I just found.
**broken link removed**
I think you can put the photo transistor as a voltage divider at the base of a transistor and it can work as a switch (Instead of using the op-amp).

 

A

ApplePiePod

New Member

• Jul 30, 2009

• #4

Can I get dome help modifiying

**broken link removed**

to work with 9 volts?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Jul 30, 2009

• #5

Remove 12V supply, fit 9V supply - it's not difficult.