Analogue input 0-10V DC or 4-20ma DC measure circuit.

parth kothiya · ‎2022-04-05

I want to measure analogue input ( 0-10V DC , 4-20ma) using STM32 MCU.

STM32 pin ip voltage (0-3.3)

Now I want to convert 0-10V & 4-20ma in to (0-3.3V DC) what is the circuit diagram for getting 0-3.3V output ?

Peter BENSCH · ‎2022-04-06

This can be done quite easily by connecting both a resistor in series to the ADC input and two Schottky diodes:

from GND --> ADC input
from ADC input --> VDD

The first limits negative input spikes, the latter diverts positive voltages with more than VDD+Vf to VDD. Both ensure that the input voltage remains within the permissible range because of the small forward voltage of Schottky diodes.

The resistor limits the current that can flow through an overvoltage, so its size depends on the expected overvoltage. If you use a voltage divider to measure the 0...10V, you can usually do without the series resistor.

Regards

/Peter

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View solution in original post

Peter BENSCH · ‎2022-04-06

You asked essentially the same question as you have asked before.

Regards

/Peter

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parth kothiya · ‎2022-04-06

How can I protect MCU pins if input analogue voltage is greater than 3.3 voltage?

Or how to limit voltage divider op not increase then 3.3 voltage when ip voltage is increasing grater then 10v.

Example

IP........OP

0V. 0V

10V. 3.3V

12V. 3.3V

Peter BENSCH · ‎2022-04-06

This can be done quite easily by connecting both a resistor in series to the ADC input and two Schottky diodes:

from GND --> ADC input
from ADC input --> VDD

The first limits negative input spikes, the latter diverts positive voltages with more than VDD+Vf to VDD. Both ensure that the input voltage remains within the permissible range because of the small forward voltage of Schottky diodes.

The resistor limits the current that can flow through an overvoltage, so its size depends on the expected overvoltage. If you use a voltage divider to measure the 0...10V, you can usually do without the series resistor.

Regards

/Peter

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Peter BENSCH · ‎2022-04-06

If the problem is resolved, please mark this topic as answered by selecting Select as best under your preferred answer. This will help other users find that answer faster.

/Peter

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