Updated Case for Multi-Expansion Board

[admin]

A resistor will limit the current, not the voltage. So, a resistor will have a limited affect on the speed. Using a resistor will work up to a point where the fan won't turn on, but will have a minimal affect on the speed difference and that will vary from fan to fan. Start with a small value, like 100 ohms. That would reduce the max current to 50mA.