Re: Newbee: Optocoupler to BasicStamp


"Sam" <N@xxxxxxxxxx> wrote in message news:1128650145.897554@xxxxxxxxxx
> I just ordered some 4N28s. While I am waiting for them to arrive I thought
I
> would play around a bit.
> I just cracked open a mouse and removed the photo transistors, but cant
get
> the circuit to work.
>
> I have the center leg (base?) going to the input on my Stamp it is also
> pulled up by a 10K resistor.
> I have tried grounding both (not at the same time) other legs of the
photo
> transistor, straight to ground and also through various resistors.
>
> I cant get the Stamp to detect on/off states. Any suggestions on where my
> circuit went wrong?

Offhand I would say you leave the base open and connect the other two leads
to the Stamp. The collector (probably need a pullup resistor) goes to an
input and the emitter goes to the ground or common of the circuit.

The input to the base of a transistor is what normally turns it on. In the
case of a phototransistor the base is left open (in most cases) and its
input is the light (photons ?) .


.

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