Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to multiplex signal from multiple sensors

  1. Feb 24, 2012 #1
    I have a bunch of photodiodes and I want to interface to these to a computer using my sound card. I have 12 sensors and stereo input samples at around 96000hz. My idea is to connect 12 sensors to each line and have them turn on or off at a specified offset so that the total output signal would be sensor1,sensor2,....sensor 12. I can then split the signal up in software (I only need around ~500 hz for each sensor)

    Is that a good way of doing it or do you think there is an easier way? How difficult would the precise synchronization of turning detectors on/off would be?

    I was thinking of using a bunch of 555 timers but need a way to synchronize them or set the phases
    Last edited: Feb 24, 2012
  2. jcsd
  3. Feb 26, 2012 #2
    The easiest way to go about doing this is to just use an off the shelf USB data acquisition device.

    Otherwise if you need the sensors to connect to your sound card, consider using an analog multiplexer IC to cycle between each sensor and interleave the analog data onto a single output line.

    To synchronize the output signal with your software, use a sync break in between each round of sampling. You could leave an obvious time delay between sensor 12 and sensor 1. Or you could have an unused channel 13 that outputs some reference voltage that indicates the start of a new frame.
  4. Mar 9, 2012 #3
    You might look into a fairly consistent oscillator, maybe a 32.768kHz. Then put it through a divider and have a divide by four select a 1-16 must. As ST said, make one of the 16 channels a reference value and use it for synchronization.

    I don't think your sound card is DC coupled, so you may have to introduce one channel as a ground value, so you can use it as a baseline to correct for the offset in the other values.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook