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[DPRG] Controlling 4 Polaroid (SensComp) Sonar units

Subject: [DPRG] Controlling 4 Polaroid (SensComp) Sonar units
From: Duane Brantley d-brantley at sbcglobal.net
Date: Thu Jan 7 13:02:28 CST 2010

A staggered firing pattern, makes sense.  

The instruction for the SensComp (Polaroid) Sonar unit says MAX range is 35 feet.  I don't really need to look that far.  I just want to make sure things don't get too close!


From: "deltagraph at aol.com" <deltagraph at aol.com>
To: d-brantley at sbcglobal.net; peburrell at yahoo.com; dprglist at dprg.org
Sent: Thu, January 7, 2010 12:24:32 PM
Subject: Re: [DPRG] Controlling 4 Polaroid (SensComp) Sonar units

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 modules.
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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