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Electromyography is a technique used for recording the electrical activity of a muscle. In order for a muscle to move, it must receive an electrical signal from the brain via a motor neuron, with the frequency of nerve impulses controlling the force of contraction. This generates a potential difference on the surface of the skin (in the magnitude of 30micro - 50millivolts)* which the EMG circuit can pick up and amplify to around 1-2V, allowing it to be easily read on an analog pin of a microcontroller such as Arduino.
The simplest EMG circuit has 3 electrodes and can measure the electrical activity of one muscle. 2 electrodes are placed next to each other in the middle of the muscle, approx. 3-8cm apart, and the 3rd one is grounded and placed on a bone or held in hand and acts as a reference electrode. Typically, EMG electrodes are ‘wet’, consisting of a conductive gel sticker that is stuck on the muscle. and ensures a constant connection. Unfortunately, these electrodes can be a bit expensive, difficult to get, and usually not reusable. ‘Dry’ electrodes do not contain any gel and although they can produce more noisy signals and sometimes disconnect, they do are much more convenient and can be made from just a piece of metal and wire.
Materials Needed:
- At least 2-3 meters of wire, for electrodes and circuitry.
-Metal sheet (can use a drink can with the plastic coating removed)
-1x LM324n general use opamp IC
-1x 200 - 220 resistor
-3x 10k resistors
-2x 100k resistors
-2x 1M resistors
-Microcontroller (Arduino)
-Tape (for sticking on the electrodes
-Soldering iron

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