Multiple PING))) triggering question

TheGrue

I have a robot with 5 PING)))'s mounted on the front. 3 face forward and two at 45 degree angles like so:

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My question is this, do I need to add a WAITCNT command to space the calls of each PING))) so that echos from the last one don't give false readings to the current PING))) called?

PUB SensorArray

   repeat
       PngCenter      := Ping.Inches(p_CPing)
       PngLeftAngle   := Ping.Inches(p_LAPing)
       PngRightAngle  := Ping.Inches(p_RAPing)
       PngLeftFront   := Ping.Inches(p_LPing)
       PngRightFront  := Ping.Inches(p_RPing)

More details and pictures of my robot can be found here at my robot build site

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TOBI – The Tool Bot
letsmakerobots.com/node/7025/
RoBo Remote - Programmable Remote Controller
letsmakerobots.com/node/18692

Post Edited (TheGrue) : 7/27/2010 5:47:29 AM GMT

Mike Green

Yes.

You need to allow enough time so that the echoes from each PING can die out before the next one is triggered. Remember that the PING itself can respond to an echo up to 18.5ms from emitting a pulse of sound, but returns a response when the first echo is received (as early as 1ms from emitting a pulse of sound).

TheGrue

Thanks Mike. I knew that I could count on you. Do know if there are any recommended delays? I have been searching for recommendations but I have not found any yet.

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TOBI – The Tool Bot
letsmakerobots.com/node/7025/
RoBo Remote - Programmable Remote Controller
letsmakerobots.com/node/18692

Mike Green

Use common sense and physics. What's the largest space that you expect your robot to work in? Figure out the time it would take for sound to cross that space and allow 2 or 3 times that. If you don't know, use the maximum range of the PING and triple that. I'd probably round up the 18.5ms and triple it to get 60ms, maybe use 100ms, something on that order.