Help with wiring diagram!

[sethmaster]

http://imgur.com/VTsAP.png

i am pretty confused about where the phototransistor goes and why there is a wire going between the 200k and 100k resistors, its also connected to pin one of the lm358? Any suggestions?

 

[Mitchekj]

Heya,

The "wire" going between the 200k and 100k resistors are the wiper leads. Those are potentiometers, adjustable resistors with three leads. The arrow pointing into the resistor is the wiper. You can adjust how much resistance is between either terminal and the wiper by turning the pot. The wipers are tied together, and also to pin 1 on the amplifier. In the case of the 200k guy, his wiper is tied to one of his own leads, as well.

As to the phototransistor... it goes right where it says it goes. This will take an optical input, I'd assume it would go in/on the business end of whatever you're device is. This is basically turning a light level into a sound level, right? What are you trying to do with it?

 

[sethmaster]

Thanks! That helps alot. This is a signal amplifier for a laser microphone. I was reading about it a while ago and I decided to try it.