I'm building an industrial circuit, and want to use 0-10V and 4-20mA sensors in this circuit.
I want to protect my ESP32 MCU(NodeMcu board) from transients and high voltages.
I design this circuit and have questions:
-
Is this circuit works good for my purpose?
-
which component is necessary and Which one is optional(schottky diodes,100nf capacitor,polyfuse)?
-
NodeMcu does not have any Analog ground ,does it matter?
-
whats your opinion on this circuit?
It's not a precision system, but I want to protect it in a good way.
Best Answer
assuming that you modified the D3
it should be working. However you should not that in the ADC analog front end there is an internal holding capacitor. You potential divider has an output resistor of R2 approx. This may delay the charging of the hold capacitor if you have high sampling rate or high frequency signal. Attached is the ADC front end inside a microchip. It should be the same.
schottky diodes important. 100nF don't know, you should take care they attenuate your signal and add a delay(phase shift) in to your signal so you may get the wrong value of the sensor in that time. The corner frequency of this circuit is about 400 Hz. If your signal frequency is more than that the capacitor will filter out the high frequency and you will get small readings.
It may be directly connected to the Digital one. check datasheet and technical references.
You will have negative voting by this kind of questions.
I will add another resistor (1k) before connecting this circuit to the ADC. so the schottky diode will conduct most of the currents if a surge occurred in the analog side. This resistor should be as close as possible to the ADC pin in the board.