I want to make use of the Dagu 4 channel motor control board, but I've had difficulty with this device in the past. Particularly, the last one I had seems to have been overloaded and is now totally broken. Naturally I want to keep this from happening, but I'm not sure what are the proper operational ranges. The website says 4.5 to 12 volts for the motor power supply, but what about the rest? What is a comfortable power for the board itself? What would it take to overload the control logic pins? My previous set up sent 7.2 volts to the board, with 3.3 volt signals to the control logic pins.
The safe way to use it is to read the specification and find out what range of signals it is designed to accept, and then work within those levels. If it’s designed to be controlled by TTL inputs then it is probably designed for 3.3V or 5V and it sounds as if you have exceeded that rather substantially. So this time I suggest you find out what it needs before you blow it up, rather than after.
You misunderstand me. The control pins are only receiving 3.5 volts. However, the board itself needs to be powered, and the literature is rather vague on the ranges it can take.