Hello all I want to connect a pressure transducer which is 12VDC, 4-20ma output to my ESP32-C3.
Is this the correct way to wire it?
Thanks for your help!
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Hey. Welcome welcome.
That middle device looks like a buck converter? May we have a model please.
In general looks good but we need more details to be sure.
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Model is 680579955293
is this it ?
If so, your setup looks mostly ok.
The key bit will be to ensure you set the jumpers to ensure you keep the “output voltage” <= 3.3V
Based the that pages data supplied.
4–20ma:
0 - 2.5V range: J1 1,2 Jumper Short, 3,4 Jumper Short
0 – 3.3V range: J1 1,2 Jumper Open, 3,4 Jumper Open
With these sorts of things I like to test it bit by bit.
e.g. Connect the power Supply and sensor to the unit (no connection the the C3)
then measure the voltage on the V out pin and run some tests to ensure the max voltages is safe (e.g. max out the sensor).
If that looks ok, then run the ground wire to the C3 and the Vout to your Input Pin.
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The wiring looks good, but you might not get the measurements you are expecting.
There is conflicting information re the ADC for the ESP32-C3 Super Mini. Espressif is quite clear that the reference voltage used for ADC is a nominal 1100mV. Other commentary indicates a range of 0V to 3.3V, albeit with errors at the ends of the range. The board schematic does not show a divider network on the ADC pins. The datasheet does not specify a separate maximum input for the analog inputs (presumably because the analog inputs can be used as digital inputs). So it would be worth checking what the actual range of the ADC is, and using a voltage divider if needed for covering the full range available from the converter.
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Yes, that is the exact one. Thanks. Will try that first so I dont ruin the board.
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Ok, I will endeavour to get more information. Thanks.
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Hello all,
Current to voltage conversion, why not use a simple series resistor network. Check the voltage range of the ADC and set the appropriate resistor across the input for max. 20mA. If the additional series resistor is required, calculate it accordingly.
Basically that is the practice followed for years with industrial PLC’s.
Regards
Bryan
Hi All
No need for a network. That interface does all the work and outputs a voltage (range jumper selectable as Michael researched) that can be massaged if required and used in whatever way is applicable. In this case the ADC input of an MCU.
This is a bit more info on the Amazon site which indicates the output range is set with the 2 potentiometers. Not sure where Michael’s reference to the links comes from but I did not search in depth, only used Michael’s link.
About this item
- The module according to the definition of wiring, power supply voltage 7-36V (if the output to 10V, the supply voltage must be greater than 12V)
- After power-up, the D2 indicator should be on, otherwise, check the line connection. Board with reverse protection, the reverse does not burn.
- When the current input is the minimum (0mA or 4mA), adjust the ZERO potentiometer so that the VOUT output is the minimum (0.0V or other voltage)
- When the current input is at maximum (20mA), adjust the SPAN potentiometer so that the VOUT output is the maximum (3.3V or 5V or 10V, the output can be as low as 2.5V when the input is 4-20ma).
Heed Jeff’s advice. There has been others found some problems with some ADC inputs lately.
Cheers Bob
Hello all again,
In the industrial world there is mostly 2 versions of transducers used, in this case the output being 4-20mA, 1/ loop powered, 2 wires only, that is the current from 0 to 4mA effectively powers the transducer unit. This type would need an interface as is the current to voltage converter assuming the input provides a loop powered arrangement. 2/ the second unit separate power supplied unit mostly 4 wires. The power supply can be 12 or 24V or what ever. The 4-20mA output being 2 of the 4 wires can be terminated directly to a resistor with the resulting voltage applied to the ADC input.
From the ESP32 table below and using ATTEN3 the max input voltage is 2500mV. At 20mA max signal the value of R is 125 ohm. Most transducer data sheet would specify a max value of R it can drive into. In the past this would have been 500 ohm giving 10V. My simple sketch below.
Hartley initially advised he had a 12V DC transducer? 4-20mA output.
My 2 shillings for what it is worth.
Regards
Bryan
Hi Bryan
All good. It is my belief that that “interface” board would form part of what you have labeled “Transducer 12VDC 4-20mA” and includes the 125Ω load resistor.
I am not conversant with the finer details of this board but my reasoning is the 12V operating voltage is supplied to this board which would generate the loop current which in turn is circulated via the actual pressure transducer and modified by this to reflect applied pressure.
The load resistance is variable to provide the required DC output voltage. This resistance is obviously incorporated on board as the output is a varying voltage of adjustable level to suit the end use. Thus the whole thing is really a complete package and appears to be pretty versatile having a fairly wide input and output range with the only external connections being input DC voltage and out DC voltage for further use by whatever.
Not so much in the past. It has been a while but I think the “standard” PLC analog input (ADC) is still 0-10V. Could be wrong but if I get a chance I will try to find out.
Cheers Bob
