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Unread 20-09-2009, 13:48
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Re: MaxBotix Sonar Sensor - Help please

Two problems:

First, the input impedance of this circuit is far too low, which is what is dragging the sensor output down. Increase the values of the 1k and 10k/15k resistors by a factor of 10 or even better 100.

Second, this circuit appears to have a gain of -10, while you seem to want a gain of something like -(3.6/5=0.72), so the 1k and 10k resistors need a different ratio. (I could be wrong here - it's been a long time since I did this, but check into it please)

Here is a spec sheet for the LM358, study it (especially the examples at the end) and use Google to look up op-amp circuits (you want an inverting gain amplifier, even if the gain is -0.72).

Good luck!
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