Electronic – Convert 0 to -150V DC to 0 to 3.3V

microcontrollernegativevoltage

I have a signal that gives spikes up to negative 150V. I need to be able to determine these spikes using MCU that can sens 0 to 3.3V.
How can i adjust a signal so that it doesnt fry my MCU. It should be a power friendly method.

Thanks!

Here is the measurement of the spike on oscilloscope

Best Answer

Something like this should work if the source of your pulse has a reasonably low impedance. The MCU input would preferably have a Schmitt trigger input type, or add a ST buffer before the input. If the load on your 3.3V supply is at least 1.5mA it will be able to handle +150V/-500V transients (limited in the negative direction by the resistor surge rating and voltage rating). Transition (1.65V) is at about -33V, so the pulse at the MCU should be around 150usec.

schematic

simulate this circuit – Schematic created using CircuitLab