[mowbot] Infared circuit

Raymond Skarratt (skarratt nospam at ati.com)
Thu, 28 Oct 1999 12:43:17 -0400

Hello all,

I am trying to do some experimentation with IR. I went to the local
electronics store last weekend and picked up an IR LED and an IR detector.
Unfortunately I didn't get a datasheet for either one. I went home and
tried to hook up a simple circuit to see if I could get TTL level signaling

I want to make two separate circuits. The first one is a simple LED
resistor circuit and I had no problem with that. So I have the IR LED
working now (I think, at least when I put a visible LED in place of the IR
one it lights up). The problem is with the detector circuit. I have this
detector but I am not sure exactly what it is. It looks sort of like a
square black LED. I have a circuit hooked up so that there is a visible LED
in series with this detector. What I want to be able to do is have the
visible LED toggle on/off when the detector has the IR LED shining on it or
doesn't have the IR shining on it. Right now the visible LED stays on all
the time. If I measure the voltage drop across the IR detector it changes
from 4.75V or so to 4.60 V when the IR LED is shining on it. I have tried
to measure current but I can't seem to get that to work.

Does anyone have any idea of what kind of circuit I should be building. I
am thinking I need to use a transistor as a switch but I am not sure if that
is the right way to be doing this.

Thanks for any help,
Ray Skarratt