Hi All,
i have a circuit which has an input for two 9V batteries to supply it with +9V ,GND and -9V
This circuit is used to detect the EMG (ELECTROMYOGRAPH) which is the muscle contraction.
The output in relaxation is about 0.66 to 0.8 V
when i try to connect this output to arduino uno and connect the ground of the arduino to the ground of my circuit to unify the ground , the output in relaxtion jumps up to be about 1.7V .
So I dont have any info about how to make the output equal to 0.8 in both cases(connected with arduino OR not connected to arduino)
Hi, do you have the arduino powered via USB or its own supply, USB supply might introduce some earth problems.
Also the analog or digital inputs of an arduino UNO is 5V max, arduino DUE 3.3Vmax, so you may have to use a potential divider between the output of the EMG and the arduino to drop the max output.
Hi, I'm not sure, USB is produced from the switch mode supply in the computer.
Have you tried 0.1uF capacitors from analog input pins to the gnd on the arduino, it may be noise of some sort.
I don't know if the caps will change the response of the system, a small value like that shouldn't cause a problem.
Also it might be worth using shielded cable between the EMG and arduino, just as it is used on the input to the EMG.
I thought about using a voltage follower, do u think that will fix the issue?
And is it valid if i cut the usb cable for arduino and put the red to 5V and black to GND directly ?
Probably no, about the cable cutting.
The problem is at the gnd and arduino analogue input.
Have you got the gnd of the EMG connected to anything other than the arduino GND, you may need to make the arduino gnd the only gnd for the EMG, then make sure you have proper gnd at the arduino to make it medically safe.
