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How does one use the PT100 Amp Board with a 3.3v controller, eg RADDs

The documentation indicates that the PT100 needs a 5v supply and provides a 5v output.

Is this usable with a 32-bit contoller? Can it be supplied with 3.3v and hooked up to a 3.3 v input?


Thanks!

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3 Answers

Hi Duncan,

The PT100 amplifier board requires a stable 5v connection to work correctly therefore it is not possible for use with a 3.3v power input.

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A stable 5v supply is available in my system, I have one to drive the bltouch. Is there a recommended solution to scale the output back to 3.3volts? Or some other solution? It looks like the amp itself will run at 3.3v.

If not, it looks like a gap in your product line given the popularity of 32 bit controllers now.

Thanks!

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The issue is most 3.3 volt 32-bit controller chips are only 5 volt signal tolerant on their digital pins.


Placing more than 3.3 volts on an analog pin will damage the chip.


You may be able to limit the PT100 amplifier output signal’s voltage to a max of 3.3 volts by using a moderate resistance in series resistor (60 to 100 ohms 1/4watt) on the 5 volt powered PT100 amplifier signal output to limit the output current with a small signal diode (e.g. a 1N914) connected to the resistor’s other pin in reverse biased fashion to the 3.3 volt supply of your 32-bit controller board. A 60 ohm resistor should limit any current from the PT100 signal output at 5V to the 3.3V supply via the diode to 20 mA protecting your 32 bit electronics.


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Duncan Smith will be eternally grateful.
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