Device with 4-5 temperature probes (0 - 250 deg F) - what options - Arduino, Raspberry Pi?

Discussion in 'Embedded Systems and Microcontrollers' started by RogueRose, Jul 21, 2016.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    I need to be able to take the temp of 4 locations/devices, possibly 5 (not necessary but could be handy down the road). They are all fairly close to each other, 2-4 ft.

    I'm not familiar with Arduino, or raspbery Pi capabilities, but I would assume that this would be possible with that but I would think that the display/monitor would be the most difficult/expensive of the project maybe.

    Does anyone have any suggestions for this application?
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,991
    3,736
    What do you mean by "take" in, Take the temperature. Do you want to display one at a time, display all four at the same time, or do you want to record the temperatures. Do you want the temps displayed or to read it back to a laptop for display.
     
    RogueRose likes this.
  3. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,383
    495
    I have done it. My senior design project we used three termocouples to take high temperature and used one TMP36 to take regular ambient temperature.

    For termocouples we got special little boards that have circuitry on it to amplify and digitize the temperature, then we sent it to Arduino Due using SPI. This is well developed application.
    https://www.adafruit.com/products/269
    If you use the boards, you can share clock and data lines, then use digital lines from Arduino board to select individual board to read temperature.

    The TMP36 we wired directly to the Due ADC. I think most Arduino boards have 5 or 6 ADC so you can just wire one temperature sensor to the each ADC. TMP36 is Celsius sensor, you can convert the temperature to °F in the program. Or you can get °F sensor, TMP35 maybe, I have not worked with °F sensors so I don't know their model names. Again, the software for Arduino is well developed so no need to reinvent the wheel.
    https://www.adafruit.com/product/165

    With your upper limit of 250°F (121°C) you can use either method. However, it is close to limit of TMP36 so you might want to see if there is similar sensor that goes a little higher so that you have a little overhead.
     
    RogueRose likes this.
  4. RogueRose

    Thread Starter Member

    Oct 10, 2014
    189
    4
    Thanks for the replies! Basically I at least need them to display the temps. Ideally all 4-5 at the same time but I guess I could scroll through the temps with a button or something. They are for monitoring a process that has 4 different zones and each needs to be within a specific temp range.

    I guess it would be really cool if I could hook this up to a spare laptop (I have some P4's 2.6Ghz - 2-4Gb ram - I prefer Linux but can russle up a Windows license if needed) and use that as a display and maybe store the data.

    So, Ideally I would be able to:
    -store data points every 1 minute
    -set alarms when temps are reached (visual or audio alarm works)
    -possibly incorporate a power relay to turn power off if alarm is tripped
    -Moisture monitor to sense when a liquid reaches a certain level (I guess something like a float that will trip a relay/switch at a certain point - triggering an alarm/notice)


    The 250 is a super top end (run-away process I would say) and I don't expect over 200 99% of the time. Most will be 30-200F.

    That thermocouple in the second link looks like what I might be looking for but there are also ones that are just a wire, like those that attach to a CPU or RAM that would be ideal for this. I've also seen ones that attach to fridge/AC/dehumidifier/freezers, that are the size/shape that would be ideal.

    At two locations I need to place this inside a pipe (one PVC, one copper) so a "wire" type would be ideal. My multimeter has a temperature probe that is a 2 conductor wire and my meat probe has a similar one.

    I'll read over Shteii01's post a little more and see what I can work from it.
     
  5. Robin Mitchell

    Well-Known Member

    Oct 25, 2009
    732
    199
    I am working on a very similar project. Here is what I got and it works well so far:

    • PIC18F45K22
    • OLED - 128 * 64 SPI
    • DHT111 Probe (1 Wire)
    • RTC (I2C)
    • ESP8266 Module (Wifi, UART)
    • Several buttons
    • LDR (for light detection)
     
    RogueRose likes this.
  6. shteii01

    AAC Fanatic!

    Feb 19, 2010
    3,383
    495
    Termocouples output milliVolts. For this reason they are always connected to some kind of instrumentation amplifier. The thing is, you almost never see this amplifier. The temperature probe that came with your multimeter is termocouple, but the amplifier is built into your multimeter so you never see it.

    Displaying all the temperatures is not a problem. You read the temperatures sequentially, but you do it so fast that it appears like you are getting them all at the same time. If you get one of those 4 lines, 20 character lcd displays, you can show all temperatures in two columns or two rows.

    Arduino has the native ability to send data to pc. For more sophisticated approach to data logging, and if you have Excel, you can use this: http://robottini.altervista.org/arduino-and-real-time-charts-in-excel

    In case you missed it, some soldering is required.
     
    RogueRose likes this.
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    5,991
    3,736
    Get a small display for your arduino like a Nokia 5110. They are available on ebay or sparkfun for under $10. You can send your values to the display and see all four at once. You can add column headers and possibly more. Bigger displays are available if you need more space or have a bigger budget.
     
  8. DC_Kid

    Distinguished Member

    Feb 25, 2008
    638
    9
    they make temp sensors that can use a single bus, so essentially you can probe many many temp sensors via a single wire. something like a maxim DS18B20
     
Loading...