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[DPRG] Controlling 4 Polaroid (SensComp) Sonar units

Subject: [DPRG] Controlling 4 Polaroid (SensComp) Sonar units
From: deltagraph at aol.com deltagraph at aol.com
Date: Thu Jan 7 12:24:32 CST 2010

I believe that David (dpa) triggers sonar modules on jbot in a pattern  
that minimizes interference while allowing him to trigger faster then the  
sensors individual "MAX listen for echo time". Beam width,  angular  separation 
and sonar range can all affect max rate at which you can trigger  sonar 
Some experimentation might be needed, but probably good idea to know MAX  
range on modules. Also, some modules are capable detecting multiple 
reflections.  I have played around just enough to know that filtering measurements 
seems to be  very important.  On sensors that return a pulse width you might 
need to  multiplex sonar outputs to controller pin that is used to measure 
pulse width. 
MaxBotix sonar modules have the ability to be daisy chained. I would guess, 
 without looking at their specs, that they wait until longest expected time 
to  hear an echo before triggering the next module. Therefore if you have a 
radial  array of say 4 of these these sensors you would need to manually 
trigger to  speed up the rate, e.g. 1234 you might trigger 1 4 2 (delay) 3 1 4 
2 ...
Note added delay between 2 and 3 because they are adjacent.
Hope this makes sense.
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