At first glance battery low alarm seen on the screen as if 12v given to detector for this replace R19 value 22k to 18 k.
But 18 Volts must be supplied to the detector for proper working. Also can work best on 24 VDC.
Video : https://www.youtube.com/watch?v=RlMi2n-AguY
complete circuit available at
https://felezjooblog.wordpress.com/2017/12/17/felezjoo-pi-metal-detector-fpi/
Check detector performance
Click on below
KSF Electronics 
Hello,Very interested in the Felezjoo PI but for my application I need a way to monitor the current readings and settings from the ATMEGA in real-time and transmit that data to an Arduino based device (maybe through SPI?). I know code is not open source and only the hex file is available to public. Any idea if this is possible and if so, how you would recommend I go about it?Thanks!Brian
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This will be my next project, one of my friend also demand me about this type of project, but you can find this type of circuit through net like arduino to arduino link through 433 MHz type trans receive modules or x bee like.
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Wrora ma ta da felezjoo original file pa kar dai meherbani wakry rawalaza kawi ta Sara shukriya.
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