heartbeat simulator/tester/calibrator (ECG waveform generator)

Discussion in 'The Projects Forum' started by Azzy, Oct 17, 2010.

  1. Azzy

    Thread Starter New Member

    Oct 9, 2010
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    Hi, I’m trying to generate a signal that looks like a heartbeat, couple mV, and somewhere around 60Hz, I used LM555(Timer) to generate a pulse satisfy the criteria, but need to shape those pulses that my look close to a heartbeat signal. Please if you guys have any suggestion I will try it, or some other circuits that may work for the same purpose I will appreciate it.
    Thank you all
     
    Last edited by a moderator: Nov 5, 2010
  2. beenthere

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  3. retched

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    Go for audio, and play the recording back.

    You will have a _TIME_ trying to manually shape the signal.

    AND you should have a heart to record right there in your chest. ;)

    A decent DSP PIC or other flavor can speed up or slow down the audio playback to be triggered by an external trigger..like your 555.
     
  4. KMoffett

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    To go with beenthere's post, this is a UJT based ECG rate/amplitude calibrator that I designed as a student for a Biomedical Electronics class back in the 70's.

    I have another one that a friend made with 555s that replicated actual 12-lead waveforms. I'll have to dig that out.

    Seems like that a microcontroller with a look-up table and a filtered PWM output would be the way to go now.

    Ken
     
  5. KMoffett

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    Here's a BP/ECG simulator designed by my friend, John Kruse, VA Hospital, back in 1976.

    Ken
     
  6. Azzy

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    Oct 9, 2010
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    thank you all
     
  7. jpanhalt

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    If it's normal, why do you need to simulate it? Do you eventually need to simulate abnormal heart beats?

    John
     
  8. Azzy

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    Oct 9, 2010
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    The reason behind simulating a heartbeat monitor is the fact that the monitor has some electrical current running through it and for the safety and precautions, the monitor needs to be tested before a patient can use it.
     
  9. jpanhalt

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    One of the oldest adages of medicine is, you look for what you know and you find what you look for. Why would a potential patient want to listen to a normal heartbeat? I will bet they will miss Kentucky or Tennessee (etc.), if all they have heard is the normal rhythm.

    John
     
    Last edited: Oct 22, 2010
  10. Azzy

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    Oct 9, 2010
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    Actually, they are not going to be listening to the rhythm of a heartbeat, they will test the ECG monitor, on their simulator to see if it’s working properly then they will plug to a computer to send the waveform to the hospital so doctors can monitor the stability of their heart from home.
     
  11. Audioguru

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    Dec 20, 2007
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    After I had a heart attack 1.5 years ago my heart has an slightly abnormal rhythm.
    Two of the arteries feeding my heart were blocked causing the heart attack but got fixed soon in an angioplasty operation and later tests showed no damage to my heart.

    But now my heart occasionally skips a beat or two then later adds a beat or two. The doctors say that it normally happens to some people and don't know why. It doesn't bother me because I feel fine. I wore a portable ECG monitor for 48 hours as a test of my heart rate. I also wore a blood pressure monitor for 24 hours and it woke my wife and I each hour at night. The doctors also don't know why my blood pressure fluctuates (maybe because I like to eat salty foods or because I like ... never mind?).
     
  12. jpanhalt

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    You seem to be asking two questions here. One is how to produce an electrical voltage that simulates the normal heart beat detected by an EKG lead. The second is to ensure that your monitor does not subject the subject to too much voltage/current when it is attached (post #8).

    Which is it?

    John
     
  13. Azzy

    Thread Starter New Member

    Oct 9, 2010
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    I have been working extremely hard to come up with a heartbeat Simulator that can generate an ECG waveform. I almost tried everything from timer LM555 to CD4017, and UJTs anything I’ve heard of. Please if anyone has an idea I can try the due time almost up
    THANK YOU ALL
     
  14. blueroomelectronics

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    How about a MP3 player.
     
  15. kubeek

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    If you can use some kind of micocotroller, that can be quite easy. Get a recording of a real signal, and play it back by the uc, for example using 1bit D/A.
    You will for sure find some projects that will do playback, even with source files for the right microcontroller.

    ETA: MP3 player as blueroomelectronics said would be the simplest solution, but I think this task is some kind of a school project, so making a basic wav player should fulfill the requirements. If not, then OP will spend lots of time tweaking some kind of waveform shaper.
     
  16. hgmjr

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    One technique would be to use an 8-bit wide EEPROM memory device programmed with the waveform. This would in turn be fed to a Digital-to-Analog convertor.

    This approach would permit you to speed up the clock or slow it down in order to simulate different heart rates.

    hgmjr
     
  17. jpanhalt

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  18. bertus

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  19. kubeek

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    From the thread you opened a couple weeks ago it looks like you didn´t really try everything you could. If you for example stated what exactly does make an ECG "up to standard" i.e. what criteria must if fulfill, you would have gone a lot further.

    My idea is that to test an ECG if it is displaying the measured voltages correctly, you don´t need to provide a true heart´s waveform. Some simple waveform to check for example slew rate, amplitude and noise immunity is a LOT simpler.
     
  20. jpanhalt

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    We still don't know whether this project is to ensure patient safety from shock (see: http://forum.allaboutcircuits.com/showpost.php?p=288848&postcount=8 ) or as some sort of calibration for the instrument.

    I suggest these threads be merged. There are several solutions in the earlier thread from KMoffett that might be relevant to this renewed endeavor.

    John
     
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