PING ))) eco problems

David Alvarez C

Hi, I wonder why the eco pulse I receive from the sensor·is only 0.5 volts, I·had connect the signal to my micro MC68HC908GP32, I am connecting the PING))) to 5 volts as the data sheet indicates, but something must be wrong, because the eco pulso must be 5 volts right?
·
Thank you for your advice

Mike Green

The echo pulse is normally 5V (or slightly below that).

1) Somehow the scope is set wrong (most likely) and you really do have a 5V pulse.

2) There's something odd about how you've connected everything together. You'll have to post a diagram.

3) The PING))) is somehow damaged or there's a error in its manufacture.

Logic like the PING))) rarely fails with a low output voltage. It either works or you get nothing.
Maybe the microcontroller has a problem or is programmed incorrectly so it's shorting out the PING)))'s output.

Post Edited (Mike Green) : 11/6/2008 1:34:56 AM GMT

Chris Savage

I’ve seen this scope reading before…usually from college students experimenting with the PING))) using a scope and a pulse/signal generator. The problem in this case is that the signal generator is asserting the line so the PING))) cannot drive the line for the return pulse properly. My guess is you are not setting the I/O pin on your microcontroller to an input immediately after the trigger pulse. As an output, it would fight to keep the line low against the PING))) which has an internal series resistor.

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Chris Savage
Parallax Engineering

David Alvarez C

You are totally right, that was the problem.
I fix it this morning.

thanks for your help guys .

Tracy Allen

You've already solved the problem, but this result can come from having a 10x 'scope probe when expecting a 1x reading. The coincidence that caught my attention was a beautiful 0.5 volt reading when you expected 5.

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Tracy Allen
www.emesystems.com

Post Edited (Tracy Allen) : 11/6/2008 11:14:10 PM GMT