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Originally Posted by dddriveman
we are using it to power a small motor connected to a 5v output. I am not sure what the impedance is.
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D,
I am going to go out on a limb here and guess that you have a 5 volt motor you are trying to turn on with a logic digital output switching between 5 volts and ground. You are running into a problem that the motor won't start by itself even though you are sure the digital output is going to 5 volts when you want it to. So here is one method to get this working, it will allow turning in only one direction though. You need a NPN transistor capable of the current needed by the motor to run. I like 2N3055 but they are big and clunky (TO-3 case). Connect one terminal of the motor to the power supply 5 volts. Connect the other side to the collector of the transistor. Connect the emitter of the transistor to power supply ground, and connect the base to the digital output.(It may be wise to start with a 1000 ohm resistor in series with the base lead.) When the digital output goes high, the transistor collector and emitter will act as a short, grounding the lead of the motor attached to the collector. The motor is now effectively connected to 5 volts and ground. If the motor is turning the wrong direction, simply reverse the leads of the motor. Does this help?