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Sweat monitor using electrodes.

Discussion in 'General Electronics Discussion' started by JPU, Sep 12, 2012.

  1. JPU

    JPU

    281
    1
    May 19, 2012
    LOL...Thanks:p

    How are you feeling?
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Better today than yesterday.

    Thanks,
    Chris
     
  3. JPU

    JPU

    281
    1
    May 19, 2012
    Hi chris

    I have been asked the impedance of the circuit?

    I have had look into ths and it looks like nightmare to work especially as the circuit has two supplies. Can I use Tina to work out the impedance..

    Justin
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    The impedance of what circuit? The heart rate monitor or the sweat monitor? Input Z or output Z? Who asked and where was it asked?

    Chris
     
  5. JPU

    JPU

    281
    1
    May 19, 2012
    Hi Chris

    I asked for help also on the Picaxe programming from the Picaxe forum. I have to be honnest with you though, I think I was way to "get up and go" and after a wasted day today I think I will have to come back to you "cap in hand" as my signal capture/amplification circuit needs much more work. As I think, you implied! Today, I seem to have had nothing but noise and the odd peek or two. It is very hit and miss on the capture side!!

    Edit: I have just noticed your post regarding the ADC programming in the other thread..This thread jumping is getting confusing and its my fault!!! However I am going to make a start on the program as it will still be necessary regardless of the capture quality. There has been mention of an ST which I have tried, in the other forum. However and this is the most resent thought, I think I will go with your suggestion of continuing with the ADC method...It will be a learning curve anyway!

    Here is the Picaxe forum link:

    http://www.picaxeforum.co.uk/showth...pulse-counter-help-please&p=217383#post217383

    Just
     
    Last edited: Sep 23, 2012
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Keep your new topic to discuss your heart monitor and use this thread to discuss this.

    [​IMG]

    Which I posted here.

    https://www.electronicspoint.com/sweat-monitor-using-electrodes-t252095p3.html#post1493021

    Justin, I spend time drawing and spicing things for you to only have you ignore them. Take the time to re-read this thread starting here..

    https://www.electronicspoint.com/sweat-monitor-using-electrodes-t252095p3.html#post1493021

    The signal voltages coming off the human body are in the microvolt region. Ambient mains noise is much greater in amplitude.

    Chris
     
  7. JPU

    JPU

    281
    1
    May 19, 2012
    Chris

    I think I got a bot caught up in the excitement of making my circuit and actually getting a result. (as bad as it was!)

    You are right, I did gloss over the posts you have re-pointed me to but I assure you it was not intentional. You know me by now to be very impulsive!! I just wanted to get on with getting the prototype out there.. Now I know, I am quite a way off!

    So cap in hand Sir,,,The OPA134s have arrived today and I have created the circuit you have shown above in Tina. I realise that, we have to get rid of the noise and also improve the signal by using a differential circuit. I have also read and taken on board your advice.

    What are your thoughts and what do I need to do from here. I think "scrap the existing circuit and start again!!!"

    Edit: I couldnt find the opa134 though!! is it in Tinas default list of op amps?

    Edit: Found it!! I had to do a search as it wasn't on the op amp list?

    Edit: Nope,,,I'm having a job to finish the Tina circuit, I think its a problem with the +5v and -5V,,How do I do that bit?? It doesn't seam to want to work...

    Thanks

    Justin
     
    Last edited: Sep 24, 2012
  8. JPU

    JPU

    281
    1
    May 19, 2012
    Hi Chris

    I'm having problems..

    Here is the circuit and I cant get it to do a transient analysis. I couldn't work out how to do the +5v and -5V so I tried it this way? Where have I gone wrong?

    Here is the Tine file: http://dl.dropbox.com/u/7717360/opa134 from chris.TSC

    Thanks

    Justin
     

    Attached Files:

  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Let's start by discussing the OPA134 spice sim. Did you run a Transit plot? If so, do you understand the results?

    Chris
     
  10. JPU

    JPU

    281
    1
    May 19, 2012
    Hi Chris

    Thats just it, I cant run the transit I keep getting an error. Can you take a look at the file I have in the drop box. I am fiddling with it as we speak but I keep getting "convergence problems" and a hint tells me its to do with the opa134??

    I am lost!

    Just
     
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    It's no wonder you're having problems. You have the Transit Time set from 0 to 50M. That's 50 Million Seconds! It should be 50m. You made the same mistake on the AC voltage setting for Vsig. 'M' = Meg or Million while 'm' = milli or millionths.

    Lastly, if you use voltage pins for the supplies, as I did, you have to click on the properties of the negative supply pin and put a '-' in front of the 5. Yes, it's one of those "duh" moments but we all have them. :p

    One note here. You'll find the when you enter "-5" on the -5V pin it will display both a + and - on the schematic. You can eliminate the + symbol by right clicking on the Vpin and select "Edit Symbol". Double click on the label property and delete the +. That's what I did and is why you don't see a +- on my schematic.

    Chris



    Chris
     
  12. BobK

    BobK

    7,609
    1,648
    Jan 5, 2010
    Whoa! Did virtual smoke come out of Tina when you fed Megavolts into an op-amp?

    Bob
     
  13. JPU

    JPU

    281
    1
    May 19, 2012
    Thanks Chris:p:p:p

    Here is the output I am getting now. Im still confused as VF1 scales is not the same as yours and also you have both noise waves included,,how did you manage that?

    Justin:confused::p
     

    Attached Files:

  14. JPU

    JPU

    281
    1
    May 19, 2012
    Ha ha,, I feel stupid enough,,Thanks:D
     
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    648
    May 8, 2012
    Actually, the Pro version of Tina includes a quasi virtual smoke test but the cost difference between Tina Classic and Tina Pro is known to induce heart attacks.

    Chris
     
  16. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Not sure. I'll have to check your TSC. file again. I hope you didn't blow the chip! What version of Tina do you have?

    Chris
     
  17. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    I see it and you did it again!!!!!!!!!!!!! Look at the value of R1.

    Chris
     
  18. JPU

    JPU

    281
    1
    May 19, 2012
    Yes you are right....done! (the electronics malarkey is very exact!!)

    How do you get the two noise waves to be shown?

    Just
     
  19. JPU

    JPU

    281
    1
    May 19, 2012
    Chris

    I am going to have a go at this..

    I can see that the op amp has a gain of 10.

    The signal and the noise combine with each other to reduce the wave and also to increase the size of the wave depending on position. So, as the signal is being multiplied by a factor of 10 these slight deviations due to noise are magnified greatly. Which means my circuit must have been magnifying the noise by 10s of 1000s.

    I can see that we must somehow remove the noise before we attempt to magnify the signal.

    Am I getting this..(sorry for the layman's speak)

    Just
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    648
    May 8, 2012
    Yes, electronics is an exact Sinus.
    You can separate the plot curves by clicking View - Separate Curves on the tool bar in the plot window. Let me know that you did it and we'll do the next step.

    Chris
     
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