I have a fan I'm trying to control using a Yourduino RoboRed. The fan is a 600W radiator fan from a Mercedes Benz. The fan has 4 wires two large cables are connected to the battery at all times. It has a smaller wire that is connected to +12V with the key on to activate the high power fan controller. And finally a PWM signal wire. I have successfully been able to control the fan with a wave form generator as shown in the video below. I have also been able to control it with the Arduino with the exception that when I turn the fan off the Arduino will not reset itself unless I momentarily disconnect and the PWM signal wire from the Aurdrino. This appears to be cause by voltage leaking from the high power module into the PWM circuit. Measuring the voltage on the PWM signal I find it to be ~2.5V with the Arduino connected. It measures 12V at the wire on the wire on the High Power module when the PWM wire is disconnected from the Arduino.
So I have two questions.
1) Is this leakage normal.
2) Can I stop this voltage from getting back into the Arduino with a diode. And if so how do I size the diode. I know the PMW circuit runs at 5V PWM at 10 Hz. While in operation I measured 75mA of current. The PMW wire is the blue wire in the schematic below. In the video it is the white wire.
So I have two questions.
1) Is this leakage normal.
2) Can I stop this voltage from getting back into the Arduino with a diode. And if so how do I size the diode. I know the PMW circuit runs at 5V PWM at 10 Hz. While in operation I measured 75mA of current. The PMW wire is the blue wire in the schematic below. In the video it is the white wire.
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