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Cheapest way to get data from multiple(100s) of sensors?

Discussion in 'Sensors and Actuators' started by Steve Peart, Jun 23, 2016.

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  1. Bluejets

    Bluejets

    4,053
    847
    Oct 5, 2014
    Arduino output pin will only handle 20ma max and 2803 is open collector
     
  2. Steve Peart

    Steve Peart

    51
    3
    Sep 16, 2015
    @Bluejets: I am not entirely sure what you are hinting at but i was under the impression that a darlington setup would increase the voltage and amperage of whatever is being sent into it. Typically to roughly double the voltage, so I am unsure why it's reading 0.63V when the voltage applied is ~4.9V
     
  3. Steve Peart

    Steve Peart

    51
    3
    Sep 16, 2015
    So should I be using the "output" channels on the 2803 as the GND for the LEDs instead of as the positive voltage? I switched around the wires on one after you mentioned it being an open "collector" and things appear to be working.

    Is that the correct way to handle it?
     
  4. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    0.63V should be fine.
    What is the value of the resistor in green?
    Please measure the voltage on it.
    Is the Transmitter LED polarity o.k?
     

    Attached Files:

  5. Steve Peart

    Steve Peart

    51
    3
    Sep 16, 2015
    @dorke:
    What do you mean by resistor in green?

    For now, I have been using some red LEDs so I can see that it's working before i use the IR Transmitter LED. If I line the 5v from the arduino to the resistor before the LED, then the resistor to the LED, then the cathode of the LED to the ULN2803, it lights up (when the shift register pin enables).
     
  6. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Look at the schematics attached in #84.(the resistor is marked in green).
    I think you should connect the 5V directly to your 5v power supply(may be fused) not the Arduino.
     
  7. Steve Peart

    Steve Peart

    51
    3
    Sep 16, 2015
    Oh i missed the attachment, the resistor there is the one that the LED is using, which is 200ohms for this LED, the Voltage, when enabled, is reading: 4.87V leading up to it, and 2.73V after it.

    The 5v line I have it connected to on the arduino, is the 5V always on line. Shouldn't that be ok? I don't have a power supply hooked up to this at all, it's running from the USB power of my laptop at the moment.
     
  8. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    So you have:
    VR200=4.87-2.73= 2.14V
    ILED=IR200=2.14/200=10.7mA

    That current should be fine.

    You do need to calculate the total current that the full circuit consumes,
    as long as it is below 500mA you can use the USB alone for the 5V supply.
     
  9. Steve Peart

    Steve Peart

    51
    3
    Sep 16, 2015
    UPDATE! (finally):

    I finally got some more time to work on this project and got the prototype for the sensor board running standalone. I am building my own CNC machine to make a ton of these circuit boards as small as I can so I can make a table surface from them.

    Just a small step, but progress! Thanks to everyone here so far, this has been a major learning experience for me. I am sure I will have more questions and progress to post on this soon, so stay tuned!

    Pictures of the sensor working!
    Image uploaded from iOS.jpg Image uploaded from iOS (1).jpg
     
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