Read 4-20 mA from MCP4725 using RPi

gman · November 5, 2020, 8:44am

Hi,

I am using the 1-Channel 4-20mA Current Loop Transmitter I2C Mini Module (MCP4725) with a raspberry pi (with I2C Expansion Port) to power a valve using 4-20 mA. I use python smbus to write to the DAC, however, it seems like I need a power supply of 6 V in series with the output in order to receive correct measurements. Is this correct or have I misunderstood something?

Thanks in advance!

Bhaskar · November 5, 2020, 2:53pm

Hi,
It does not require 6V supply. it should work with 5V supply.

Thanks

gman · November 5, 2020, 3:12pm

IMG_6702.HEIC (1.7 MB)

I have the following setup, so an extra supply on the output is indeed necessary for it to work?
Thanks

Bhaskar · November 5, 2020, 3:14pm

Yes, you will need a loop power supply to power up your 4-20mA device.

I use this code for testing

github.com

bhaskar-anil429/0-10V-DAC/blob/master/MCP4725.py

import smbus
import time

# Get I2C bus
bus = smbus.SMBus(1)
# 0x60 --- i2c address
# 0x41 -- DAC cahnnel one
while True:
    for i in range(0,4095):
        data1 = (i>>4)
        data2 = (i&15)<<4
        data = [data1, data2]
        bus.write_i2c_block_data(0x60, 0x41, data)
        time.sleep(0.01)
        print "Writing on DAC %d DAC value " %i
        i = i+1