bartya43
Posts: 8
Joined: Thu Apr 26, 2018 10:05 am

ADS1115 sensor Interfacing with Raspberry Pi

Thu Apr 26, 2018 10:36 am

I am using ADS1115 sensors interface with Raspberry with industrial temperature sensors but while using reference code when I am checking the value in OS command of Raspberry Pi it continuously giving the value of 2.5V continuously, when there is a change in temperature, the voltage variation does not takes place.

Please help me out where I am facing the problem

Thanks in advance

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KLL
Posts: 1453
Joined: Wed Jan 09, 2013 3:05 pm
Location: thailand
Contact: Website

Re: ADS1115 sensor Interfacing with Raspberry Pi

Thu Apr 26, 2018 2:10 pm

-1a- how you connect the ADC to the raspberry?

-1b- did you get it running,
work on range 0..4 V
testing with some voltage signal in that range?
whats your code

-2- the 2 wire 4 ..20mA sensor
how you want connect it?
what resistor you used?
with the official 250ohm it would be (0) 1 .. 5 V signal.

what power supply you used?
should be 12 .. 24VDC

you know that the 2 not really fit, but you could make that.

bartya43
Posts: 8
Joined: Thu Apr 26, 2018 10:05 am

Re: ADS1115 sensor Interfacing with Raspberry Pi

Mon Apr 30, 2018 5:24 am

-1a- how you connect the ADC to the raspberry? - Using I2C connection with the help of I2C sheild

-1b- did you get it running,
work on range 0..4 V
testing with some voltage signal in that range?
whats your code - I am using this code and I didn't test it out with the range of 0 to 4 V

-2- the 2 wire 4 ..20mA sensor
how you want connect it? - I wanted to connect it with 4-20mA temperature sensor with I2C based current loop receiver
what resistor you used?-
with the official 250ohm it would be (0) 1 .. 5 V signal. - Not using any resistor, directly connected current loop receiver with raspberry Pi I2C sheild and configuring the mentioned code

what power supply you used?
should be 12 .. 24VDC - 24VDC

but I am not able to understand why its showing 2.5V every time while running the code

User avatar
KLL
Posts: 1453
Joined: Wed Jan 09, 2013 3:05 pm
Location: thailand
Contact: Website

Re: ADS1115 sensor Interfacing with Raspberry Pi

Mon Apr 30, 2018 7:28 am

i have a bad feeling,
with I2C based current loop receiver
but you link to 4 single ended / 2 differential input with max ±4.096VDC
  • you must go back to step -1-
    and verify that the 0..4?8?V ADC and your code works ( without the sensor hardware )
    and verify that 0 and 3v3 volt is shown correctly
  • if you connect a 2 wire sensor ( 24VDC powered ) to a ADC without the proper resistor
    you actually did put 24V on the ADC input ( so it might be damaged )
    ( again go back -1- and test )
  • if you connect it with the 250ohm measuring resistor ( what is used on all industrial 4..20mA loops )
    you get a signal range of 1 .. 5 V ( on a adc input ( 0 ..4 V ) what still not work fully ), so a smaller (200ohm)
    resistor would be required.

    • there is a old trick how to measure 4 ..20mA in loops without opening them,
      you build in a diode (permanently)( on the high side /between sensor and resistor or 24vdc and sensor )
      and for measure you press the leads from the mA DMM over the diode contacts.
      the measuring current will commute from diode to measuring instrument and you can read the mA
  • pls. show us the circuit drawing how you wired all up, or ask here how to connect

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