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i have a beaglebone card, a temperature sensor PT100 and a temperature conditionner. I'm new in beaglebone, as i see the ADC is already in beaglebone but the voltage is mx = 1.8V With my industrial temperature sensor, i connect the power supply 24Vdc, connect the PT100 then the output will be in 0 to 10V

What circuit do i need to interface the temperature conditioner with beaglebone card? Should i use a voltage divider? if yes can someone guide to a basic diagram. Should i use LM317 as voltage regulator? I found this circuit in internet.enter image description here Thank you

Ian
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  • Yes but i have to see how i can get temperature values when i get the output. –  Jan 08 '19 at 16:26
  • You have two very separate issues - 1) get the temperature sensor connected to the BeagleBone without blowing it up, 2) read the analog input from within Linux (or whatever you're using) - deal with #1 first. – Attie Jan 08 '19 at 16:33
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    But yes, a voltage divider would be a good and basic way to connect it, and no an LM317 would not be helpful for connecting the 0-10v output to the ADC... – Attie Jan 08 '19 at 16:33
  • thank you, is this thread closed now? if LM317 would not be helpful, which component should i use. –  Jan 08 '19 at 18:12
  • Is there another way to regulate 0-10V to 0-1.8V for beaglebone ? – Ian Jan 09 '19 at 01:56

1 Answers1

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The LM317 is not what you are looking for. It's a voltage regulator, it does not translate a voltage level, but it does generate a stable output voltage, even with variable input.

What you need is voltage level translation, as provided by e.g. a level shifter or a voltage divider.

  • Voltage divider
    • simple
    • needs careful dimensioning to avoid problems
    • in case of BBB needs precautions like a Zener diode to clamp the input voltage to never exceed 1.8 Volt.
  • Level shifter
    • more complex
    • safer
    • output voltage range can be set by feeding in V_ADC
    • Needs a reference voltage for the input side

For controlling relays with the BBB you can use its GPIO functionality. Note though that you can NOT drive relays directly from the GPIO pins as their current consumption generally exceeds the pin drive capability of the AM335x SoC on the BBB! You must either use relay modules with built in drivers (transistor or better an opto-coupler) or attach a transistor/optocoupler (module) between each GPIO pin and relay.

Feel free to ask for clarification or further pointers.

TBR
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  • Thank you TBR, yes it should be controlled by the BBB. The BBB need to retrieve the value from the temperature sensor and then control a relay for actionning a heater or dc motor. – Ian Jan 11 '19 at 03:24
  • Added relay drive explanation to the answer. – TBR Jan 11 '19 at 09:07
  • @TBR: A level-shifter is not what OP Needs. Don't know what you mean by level-shifter but commonly it means a converter for **digital logic levels**. Just read the Wikipedia article you've linked :-) OP, however, needs a converter for an analog signal in the range of 0..10V into the range 0..1.8V. Either a simple voltage divider or a voltage divider with OpAmp buffer will do. – Curd Jan 11 '19 at 09:52
  • Yes i tried a basic voltage divider and it works, but i need elaborate the circuit to protect the BBB adc – Ian Jan 11 '19 at 13:36
  • This link was very usefull : https://www.teachmemicro.com/beaglebone-black-adc/ – Ian Jan 11 '19 at 13:49
  • Please note that that link discusses a non-standard distribution running a specific older Linux kernel. Setting up the ADC will be different depending on the image used. The user-space IIO should be similar though. Also it might make sense to open a separate question for the software side. Maybe on superuser? – TBR Jan 11 '19 at 14:00
  • I found this ADC = ADS4229 from Ti – Ian Jan 11 '19 at 16:39
  • @curd you're right, I meant an OpAmp… will revise the answer. – TBR Jan 14 '19 at 08:05
  • @TBR i found a level shifter and adc here: -1 card= 8-Channel 0-10V Analog to Digital Converter with I2C Interface - store.ncd.io -1 card= PCA9306 I2C Data and Power Level Shifter .3VDC to 5VDC Bus Handler I2C Mini… – Ian Jan 15 '19 at 20:32
  • i suggest to close this thread, my problem is resolved and thanks for everyone. – Ian Jan 16 '19 at 14:00