EMG and robotic arms

Discussion in 'General Electronics Chat' started by bug13, Jul 30, 2013.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Hi guys

    I came across this Op amp from analog device AD8220, on P25, there is an example ECG circuit, by the look of it, it's not too hard to make a EMG circuit with this instrument op amp?

    I have no experience with EMG, but if I want to a make robot arm with simple 3 fingers and just grab/close and open action, and control it EMG circuit, it should be reasonable easy to do.

    Am I right? or is there a lot of thing that I don't know and I am just being stupid?
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I assume you are talking about cardiogram circuitry, and wish to apply it to a surface detecting system for muscle movements?

    Is this correct? If so, there will need to be sophisticated noise filtering and output response conditioning applied to the circuitry. It may not be as simple as you imagine.
     
  3. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    I am refering to EMG (Electromyography), spark fun sells a kit like this one, it looks like it's just a differential amplifier + rectifier + filter + another amplifier.

    I am thinking just a simple one channel circuit, I assume it would be difficult if more than 1 channel is needed?
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    Not stupid, just inexperienced.
    Biological signals such as EEG, EKG and EMG are very difficult to measure, single or multiple channels. That is because the signal level is very low and the common mode signal is very high. You need instrumentation amplifiers with high common-mode rejection ratio CMRR.
     
  5. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    arhh... I think I understand what you say, do you mean the differential signal is very small between two inputs, but the signal to - or + input of a op amp is very high?

    correct me if I get it wrong please, thanks!
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    Yes, the difference signal is very small, microvolts.

    The two leads from your subject to the amp inputs will pick up every TV, radio, cell phone, wi-fi, satellite and 60Hz and 120Hz mains. That is what is the problem.
     
  7. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Thanks a lot MrChips, now I understand what problems need to be solved.
     
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