johnwmillr

Hi zevinton,What are the particular difficulties you're running into with this project?I'm afraid I don't have any schematics beyond what's shown in this tutorial. My advice would be to start simple—try to assemble just the "Nerve Impulse Amplifier" shown in Figure 8. Don't worry too much about the resistor and capacitor values until you've got a working prototype put together. As long you have the right order of magnitude on those values, you'll be fine. If you get the nerve impulse amplifier working, send its output into Vin of the audio amplifier.Good luck!John

I think I combined a low pass and high pass to make a band pass filter, but I'm not sure. You mostly don't want frequencies over approximately 1,000 Hz.

Hi DeepthiR8,Sorry for not getting back to you sooner. I realize the pictures of the circuit I assembled don't exactly match the diagrams.From left to right: - Op-Amp (A) - Instrumentation amp (A) - Op-Amp (B) - Op-Amp (B) - Audio amp (LM386)The first four chips (A & B) are actually two copies of the same circuit. For both A and B, the electrode input goes into the Instrumentation Amp and from there into the Op-Amp. The Op-Amps of A and B both output into the audio amplifier. I forget now, but I *think* I added the Op-Amp chips to A and B either as bandpass filters or extra buffers. You don't have to include them.So the most simple circuit to amplify just a single muscle would only use two chips: 1.) Instrumentation amp (gets input from the electrode) 2.) Audio amp (gets inpu...

Hi DeepthiR8,Sorry for not getting back to you sooner. I realize the pictures of the circuit I assembled don't exactly match the diagrams.From left to right: - Op-Amp (A) - Instrumentation amp (A) - Op-Amp (B) - Op-Amp (B) - Audio amp (LM386)The first four chips (A & B) are actually two copies of the same circuit. For both A and B, the electrode input goes into the Instrumentation Amp and from there into the Op-Amp. The Op-Amps of A and B both output into the audio amplifier. I forget now, but I *think* I added the Op-Amp chips to A and B either as bandpass filters or extra buffers. You don't have to include them.So the most simple circuit to amplify just a single muscle would only use two chips: 1.) Instrumentation amp (gets input from the electrode) 2.) Audio amp (gets input from instrumentation amp)Let me know if that answers your question!John

Hi there,I'm glad you've found the project helpful!1) Yes, you should be able to swap in the AD620 fairly easily, since it's an instrumentation amplifier just like the LT1117.2) I don't know the specifics of the PIC 32, but you should be able to still use the EMG signal as an input. The only possible concern is if the PIC 32 sampling rate is less than approximately 500 Hz. Usually you want a sampling rate of at least 2 kHz when sampling EMG, but you can get by with about 500 Hz.I hope that helps! Let me know if you have any more questions.

Thank you! My main concern with using a bluetooth module would be the potential for it to introduce a delay between flexing your muscles and triggering the audio output. There is a maximum acceptable delay of about 10 ms when playing electronic instruments. Anything above 10 ms could be pretty frustrating to play with.If delay doesn't turn out to be an issue, then there shouldn't be any major issues with using bluetooth. The module may not transmit at the proper sampling frequency for EMG, but we don't really care about that for this application, as we're mainly just using the EMG signal as a trigger.Let me know if you have any more questions! Good luck with the project.

It should be fine to replace the LT1167 with the INA12x. Have you tried it and ran into any issues? Any instrumentation amplifier will work.

Good luck on your project! Let me know if you have more questions and be sure to post a picture here once you've finished!

Do you mean the electrolytic capacitor in the top left going from power to ground? The value of that one isn't too important, it's just to smooth any fluctuations in the power source. 250 uF should be fine.

Hi Somilya, I'm glad you found my project!Do you have a question about a specific step of the process?

Hello! It's certainly possible to build an instrumentation amplifier without the LT1167, you just won't get as good signal quality. The first digram on the instrumentation amplifier Wikipedia page (and the first image in my post) shows the basic schematic you'd need to follow. All you need is three op-amps and seven resistors, wired together as shown in the diagram. You can buy chips that combine multiple op-amps in one package, like the LM148, to save space on your board. I hope this helps! Let me know if you have questions.

Ah yes, I think I see your point. Doing a frequency analysis on the EMG signal and directly converting to pitch would be tough to do, especially on the Arduino. For my other project I just used the amplitude of the rectified signals to control both pitch and volume of the MIDI notes. Thanks again for your comments!

Check this out! https://www.instructables.com/id/Make-Muscle-MIDI-Music/

Thanks for the feedback! In this Instructable I was just going for the most basic raw EMG sound (with the usual low-pass filtering built in). But it'd be cool to modulate the EMG signal into a higher frequency range like you're describing!In one of my other Instructables I describe how to use the EMG signal to control a MIDI device. That project worked best when controlling drum sounds, but I also used it to trigger a synthesizer. Maybe this is like what you have in mind?

Thanks for the feedback! In this Instructable I was just going for the most basic raw EMG sound (with the usual low-pass filtering built in). But it'd be cool to modulate the EMG signal into a higher frequency range like you're describing!In one of my other Instructables I describe how to use the EMG signal to control a MIDI device. That project worked best when controlling drum sounds, but I also used it to trigger a synthesizer. Maybe this is like what you have in mind?

Thanks for the feedback! In this Instructable I was just going for the most basic raw EMG sound (with the usual low-pass filtering built in). But it'd be cool to modulate the EMG signal into a higher frequency range like you're describing!In <a href="https://www.instructables.com/id/Make-Muscle-MIDI-..."> one of my other Instructables</a>, I describe how to use the EMG signal to control a MIDI device. That project worked best when controlling drum sounds, but I also used it to trigger a synthesizer. Maybe this is like what you have in mind? <iframe src="https://player.vimeo.com/video/201798380?byline=0&portrait=0" width="640" height="360" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></...

Thanks for the feedback! In this Instructable I was just going for the most basic raw EMG sound (with the usual low-pass filtering built in). But it'd be cool to modulate the EMG signal into a higher frequency range like you're describing!In <a href="https://www.instructables.com/id/Make-Muscle-MIDI-..."> one of my other Instructables</a>, I describe how to use the EMG signal to control a MIDI device. That project worked best when controlling drum sounds, but I also used it to trigger a synthesizer. Maybe this is like what you have in mind? <iframe src="https://player.vimeo.com/video/201798380?byline=0&portrait=0" width="640" height="360" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>

Haha, thank you! Yes, a friend pointed that out to me while I was working on the project. I'd need a few more sensors to recreate his setup. And a few more muscles...

Thank you very much! I'm sure there's an Instructable waiting to written about that Christmas! :)

Thank you! I'm glad you enjoyed reading it!

Thank you! Glad you enjoyed the project.