See the very simplified schematic down. As what you can see: Two inputs are in the form of a DC signal. We operate each input individually. RL represents a motor. The two inputs are initialized by a micro controller. The transistor used is an NPN type (BJT) (or General Purpose one).
The problem is this: When we input one signal, the two motor spin while there should be only one of them spins.They affect each other. We do not want that.
Suggestions made by ourselves:
- Note that the signal is amplified by an op amp for each input's path. We used diodes for each input's path but it did not work.
- We tried to buffer the the power source rail but it did not work.
- We tried to create two separated power sources for each input (but with a one common ground and one micro controller) and it did not work.
- We put also diodes with each motor and it did not.
So, how can we isolate these two signals? Note that we are beginners with this.
The physical circuit is this (I am pretty sure it looks messy)