🚀 go-pugleaf

nyarko@ee.ualberta.ca (David Nyarko) writes:........
> Could I have help (circuit diagrams etc.) for an Infra-Red
> (IR) transmitter/receiver with a {HIGH} tolerance to ambient light. 

 The ambient light you wish to tolerate is:
(1) SUNLIGHT   (2) 60 cycles   (3) harmonics of 60 cycles
and you need to DETECT/MEASURE  a weak IR signal in the presence of 1/2/3.
Apply some servoing (negative feedback) to the base of the phototransistor,
to control the operating point in the presence of changes in sunlight, etc.
And you might use that servoing to cancel out MOST of the 60 cycle energy.
And modulate your IR source, at a high rate, that is not an obvious harmonic
of 60Hz (that is, 120/180/240 Hz are right out). Try 3,141.5926535 Hz instead.
The challenge is applying bias to the phototransistor without draining away
the photon-induced current. And without adding lots of noise.
Allen Sullivan
Examining how design is a process of discovery.