Help needed with switches & connections

Discussion in 'General Electronics Chat' started by uscgirl517, Jul 8, 2008.

  1. uscgirl517

    Thread Starter New Member

    Jul 8, 2008
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    0
    Hello,

    I have a question regarding switches. As part of my dissertation research, I need to hook up a pulse stimulator and an EEG machine to a test sample. I need to be able to switch back and forth between applying the stimulus to the sample and then recording an EEG reading from the sample. I don't necessarily need to record the EEG during the application of the stimulus, but I need to be able to switch back and forth very quickly. The stimulus only lasts 1 sec, and I need to be able to record an EEG both before and after.

    I have a positive and a negative lead coming from the test sample, the pulse stimulator, and the EEG machine, so I am guessing that whatever sort of switch I use needs to have places to hook up 6 wires.

    I'm pretty much learning about electronics as I go along on this project, so any help you could give me about what type of switch I need, how to hook it up, etc, would be greatly appreciated!! If I've left out any important details, please let me know--I'm not sure what's important and what isn't :rolleyes:

    Thank you!!
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    Are you looking for something automatic or manual?
     
  3. roddefig

    Active Member

    Apr 29, 2008
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    Do the EEG and pulse stimulator have control interfaces (GPIB, USB, etc.) that you could connect to a computer? If you're trying to do this automatically you'll need some way to trigger the pulse stimulator and the EEG.
     
  4. uscgirl517

    Thread Starter New Member

    Jul 8, 2008
    4
    0
    Thanks for the replies!

    Bill--At present, anything that will work is fine with me :) I had envisioned it being manual though, mostly because I thought that would be simpler for me to set up.

    Roddefig--I don't believe either of them have any sort of interface to connect to a computer. So that may feedback into Bill's question, and limit it to manual..?
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    You could probably get a telephone switch box or data switch box fairly easily, just connectorize your wires and label the front. More than enough wires and positions.

    If you need something more sophisticated don't hesitate to ask.
     
  6. uscgirl517

    Thread Starter New Member

    Jul 8, 2008
    4
    0
    Thanks Bill! I'll give that a try today and see how it goes. Thanks for all of your help.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    6 Wires huh

    That's lucky

    The standard rotary switches have 12 positions and come in the following flavours

    1 pole 12 way
    2 pole 6 way
    3 pole 4way
    4 pole 3 way
    6 pole 2 way


    Each pole is a switched wire, so you need a 6 pole 2 way switch. As your medical physics tech or college radio/electronics workshop to put one in a box for you with some terminals.

    cheers
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    That is a very slow and reliable way to go. If the switching has to be done with better accuracy as to time and duration, something like analog switches will be more like it.

    To Uscgirl - is the switching simply to isolate the EEG inputs from the stimulus? How is the process controlled? If we know everything, then we can give much better advice.
     
  9. uscgirl517

    Thread Starter New Member

    Jul 8, 2008
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    0
    Thanks for the replies!

    studiot--Good tip about the rotary switch. I looked those up online and they look like a really good idea. I'll ask around at the machine shop and see what they can do.

    beenthere--I am hoping to use the same bipolar electrode in my sample for both recording and stimulating, so i need to be able to switch back and forth between using it to record and using it to conduct the stimulus. So I want to be able to use the electrode to record EEG activity, then flip a switch and use the same electrode to apply a stimulus, then flip the switch again so that I can record more EEG activity. I'm not sure if that exactly gets at the answer to your question though, so if not, just let me know and I'll try to describe it better. :)
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Something else that may do the trick for you is a manual parallel (printer) port switch (not an electronic one). Your computer support department may have some sitting around. You will need DB25 male and female connectors to hook things up.
     
  11. beenthere

    Retired Moderator

    Apr 20, 2004
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    The thing that makes one method work and not another is twofold - timing and the magnitude of the stimulus. Can you quantify them?
     
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