He didn't change when I opem and close my hand.
This website is my Arduino code and wiring diagram:
https://drive.google.com/drive/folders/1zw8KeFZXghhGBmJSJz14jeoLL1tZ-Vor?usp=sharing
This is the website I refer to:
https://www.youtube.com/watch?v=D-6GDlvAMCI&list=LL&index=12&t=145s
Thank you so much if you can figure out the problem.
Hi Wu Po-Lin ,
in order to search in a systematic way, you'll need at least a voltmeter or better an oscilloscope.
1. Measure both supply voltages (+/-9 V) with reference to GND directly at the pins of the amplifier.
2. Measure the output voltage of the amplifier. In the video showing a working setup, the output value changes from about 264 to 313 => difference = 49. The reference voltage for the ADC within the ATmega328 is either 1.1 V or 5 V (don't know how the ADC is configured here), and it is a 10 bit ADC (2^10 = 1024 values), so an output value of 1 is equivalent to an input voltage of about 1.07 mV or 4.88 mV, and an output difference of 49 equals a voltage difference of 53 mV or 239 mV. With a digital voltmeter of 3 1/2 digits, the 20 V range has a resolution of 10 mV, and the 2 V range of 1 mV, so you should see the difference between relaxed hand and clenched fist clearly.
If the amplifier works fine, the problem has to be in the Arduino (hardware and/or software). To rule out hardware, try another board.
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