First port P0 of Digispark used to receive servo pulses (1ms-2ms) coming from the radio receiver. Next port P1 is used to drive the relay K1 thru T1 which is a low-power NPN BJT. Resistor R1 is the ...

Control was via a floating 2.4 GHz receiver, as high-frequency radio signals don’t penetrate water very far. The floating box also carries an FPV transmitter to allow the sub to be piloted via ...