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  • DIY Muscle Sensor / EMG Circuit for a Microcontroller

    I am using alligator cables directly connected to electrodes on one end and circuit on the other.

    Hi Gundanium,I am facing 2 issues with my output voltage.1. The minimum voltage (output at 0 muscle exertion) at uC end is going to 1.25V. I think this is due to some mismatch on the circuit but i ma not sure what. Increasing the potentiometer gain makes this go higher and decreasing it makes it go lower. Of course decreasing the gain to solve this problem is not an option. I was thinking of using a voltage shifter however it will only be a hack. I am not sure why this problem is happening.2. The maximum voltage at output is saturated at 3.75V. Irrespective of how much gain i increase, the output never goes above 3.75V. I think this is happening due to my supply voltage. Earlier i was using +/-9V directly from battery and output sometimes went over 5V. Today i switched to +/-5V and have...

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    Hi Gundanium,I am facing 2 issues with my output voltage.1. The minimum voltage (output at 0 muscle exertion) at uC end is going to 1.25V. I think this is due to some mismatch on the circuit but i ma not sure what. Increasing the potentiometer gain makes this go higher and decreasing it makes it go lower. Of course decreasing the gain to solve this problem is not an option. I was thinking of using a voltage shifter however it will only be a hack. I am not sure why this problem is happening.2. The maximum voltage at output is saturated at 3.75V. Irrespective of how much gain i increase, the output never goes above 3.75V. I think this is happening due to my supply voltage. Earlier i was using +/-9V directly from battery and output sometimes went over 5V. Today i switched to +/-5V and have been facing this issue ever since.I am using a basic op-amp inverter using TL072 and 5V supply from arduino to get +/-5V. I checked through multimeter, my input voltages are steady at +/- 4.88V.I see that myoware sensor only requires a 5V supply from arduino and still achieves about 0.2V to 4.8V output. Have you faced these problems before ? Is there something i am missing ? Anything you would suggest to read ?Thanks

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  • DIY Muscle Sensor / EMG Circuit for a Microcontroller

    I see. in that case you have plenty of options like digibay, robokart or kits spares. there are many other sites from where you can get standard resistors.

    If you are in India, digikey might not help. I used kitsnspares.com for most of the stuff. However there are few components like 80.6k resistor which are not available anywhere for retail. So i had to order them directly from element14 (kitsnspares' parent site). I ordered 50 pieces (that was the minimum for wholesale order).

    Thanks a lot for the tutorial. Was able to make this and the output is pretty much same as myoware sensor kit. In India it cost me about 2K. The output voltage to uC is still about 3.8V but adjusting the input voltage takes care of it. I suggest adding a trimmer with your batteries to get the +/- voltage and start with a low voltage (like 10V instead of 18) since it makes it a lot safer with these expensive parts.Nice instructions.

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  • DIY Muscle Sensor / EMG Circuit for a Microcontroller

    Thanks a lot for the tutorial. Was able to make this and the output is pretty much same as myoware sensor kit. In India it cost me about 2K. The output voltage to uC is still about 3.8V but adjusting the input voltage takes care of it. I suggest adding a trimmer with your batteries to get the +/- voltage and start with a low voltage (like 10V instead of 18) since it makes it a lot safer with these expensive parts. (Check bottom part of circuit in attached image)Nice instructions.

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  • DIY Muscle Sensor / EMG Circuit for a Microcontroller

    Hi Gundanium,I am in the middle of making this circuit. I have just made Stage 1 (Differential amplification using INA106) and Stage 2 (15x amplification WITHOUT AC coupling). I tried analyzing the output of these stages using oscilloscope.I am seeing that stage 2 output is going to about +-9V. It's like a square wave with some distortion. I am unable to understand this output. As per my understanding, the max output should go to 750mV (muscle output is +-5mV and total amplification in circuit is 150x).Is the circuit / chip flawed or will AC coupling or the next stages bring the output down ? Do you know what should the output of this stage look like ?Thanks

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