I have a fan circuit TC642 connected to a microcontroller circuit 16f1519 which is in turn connected to an rtd sensor circuit. the same microcontroller circuit drives an led output. the problem is that when i connect all of them together, something interferes with the fan circuit. is it the common ground that is affecting the circuit? what else can cause the problem...the fan circuit works fine individually but with the led circuit connected it goes haywire..