I am a college graduate that is going back to school for a degree in EE, with emphasis in electromechanical prosthetic systems. In the course of trying to teach myself and get my hands dirty, I came across Sparkfun's myoelectric muscle sensor kit (SEN-11776)(https://www.sparkfun.com/products/11776). Really neat looking product. So I grabbed a couple units, and a Arduino Uno to do signal pickups.
Sparkfun provides a user manual, with diagrams and instructions on how to set up the board, and connect it to a Arduino. They also provide a sketch that declares the pins, and does a looped read of them and outputs the read to the serial port. Here are some pics of the setup I have -
There are two issues so far, one of which I think I have figured out, but some confirmation would be nice.
1 - Sensor outputs read ~0.5 V. The datasheet seems to indicate that the output of the sensor board would be amplified and rectified up to +Vs, which in this setup is ~18V. However, when I put a voltmeter to the +signal and GND pins, it only reads ~ 473mV. I think this is because the Arduino analog pins can only handle a range of 0-5 V, so I have overloaded the circuit and that's why. When I switch the supply voltage over the Arduino's 5V rail, I was able to get a reading of ~4.2 to 4.7V. Much closer to what I would expect. This sound right to people?
2 - Regardless of the setup I use, the linked 9Vs or the 5V rail on the Arduino, I get no change in signal when the electrodes are hooked up, no matter which muscles I use it on, or how I orient the contacts. I can always read a voltage across the supply terminals, and I can read a differential on the leads of the 3.5mm connector. I have tested as many of the components as I can with my multimeter, and most of them seem to be reading something across their terminals. I can read the capacitors and some of the resistors, and all show a differential. But, no dice on getting a variable signal that tracks with any sort of movement from the muscles.
I have two of these boards, that came with electrode pads, their own set of leads and board. Both boards seem to suffer from the same symptoms, in that they do no respond to any muscle movements.
Is there something I'm missing here? Is there a way I can reasonably test board functionality to see if there is an issue with the board? Have I blown something up inadvertently? By looking at the user manual, it seems that the setup should work if I have done it correctly, which I believe I have. Any input someone can offer me would be great. Thanks guys.