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From: john larkin <JL@gct.com>
Newsgroups: sci.electronics.design
Subject: Re: IR detector system, biasing of photo diode
Date: Sun, 27 Oct 2024 10:56:42 -0700
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On Sun, 27 Oct 2024 09:03:20 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Sun, 27 Oct 2024 02:19:14 +0200) it happened Klaus Vestergaard
>Kragelund <klauskvik@hotmail.com> wrote in <vfk0u0$3u9en$1@dont-email.me>:
>
>>Hi
>>
>>I am working on an IR detector that will guide a robot into a docking 
>>station.
>>
>>A IR transmitter on the docking station transmits a beam, and 2 IR 
>>detectors on the robot detects the beam and lets the robot navigate 
>>towards the target. The working distance is a couple of meters.
>>
>>I need it to be insensitive to ambient light/sunlight.
>
>
>I use a cheap camera module to track a light source in H and V direction, and just a simple Microchip PIC : for processing
>It can, with some added code, track object forms too, like a cross or maybe a big character.
> panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
>those camara modulea are IR sensitive to some extend, sometimes you can remove the IR filter from such modules.
>It may be a bit of overkill for your application, but OTOH it can do a lot more.
>Mainly designed to detect and follow jet exhaust..
>You could uee utrasonics too, maybe even simpler, no sun problem, like a bat.
>Cheap electret mikes? or modify some ebay 1 dolalr distance sensors...
>can be used for anti-collision too.
>
> 

Right. A sonic scheme could measure the phase between two mikes to
determine the direction of the source with high resolution. That could
be an analog multiplier or a bit of code. The amplitudes would be
useful too.

One could compute direction, distance, and velocity almost for free.

No problem with sunlight!

Cheap electret mikes have gain inside, a jfet or an IC, so there would
be lots of signal to go straight into a uP ADC pin.