piclist 2000\12\15\133430a >
Thread: Ultrasonic Sensors
face BY : Dan Michaels email (remove spam text)

Fred Bailey wrote:
>I have built a few interfaces from PIC's to ultrasonic sensors. Basically, you
>ping (trigger) the transducer using a FET and a good sized inductor (1uH). You
>have to wait for the ping ring to dampen down before you can see the echo

Hi Fred,

Were you using a Polaroid transducer, or the ceramic kind? I found the
following simple ckt on the robohacking sites. Any comments?

             22K  <--- probably too large
              |              |
              c           U/S xmtr
PIC---1K-----b    NPN         |
              e              |
              |             gnd

>The echo amplifier is done with four or more op-amps in series to get about 10K
>gain in total. Many stages are used to keep the frequency bandwidth high.

Uh oh. Guess I would learn this soon as I breadboarded the ckt.
The ckts I've seen had fewer stages with more gain, but you are
certainly right. Hmmm.

>Try puting the sensor on a stepping motor and map in all directions.

Tom has stepper motors for everything :). My bot will probably
just turn its whole body [initially].

- dan michaels

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