Hi Forum people,
today I have no problem (I am lucky :-)) but I want to share something that could interest somebody here:
I have a lot of 5wire steppers in my box of electronics but I need three 4wire steppers because I want to use TMC2209 microstep drivers in order to reduce occupation of so many outputs on my processor. Has somebody wandered if it might be possible to use a 5wire Unipolar as a 4wire Bipolar stepper motor ? YES you can but there is just one little problem. The fifth wire is the middle of the 2 coils connected together and this produces a shortcut between the two complete coils of the motor. Solution: cut this connection and you have two independent coils like a bipolar stepper. Look at the fotos and you see what I´m talking about.
It works, I did it with a 28-BJY48 stepper motor.
As bipolar steppers are driven by H-bridges the unipolar middle coil connection always is at mid voltage and does no harm if left unmodified.
It also should be mentioned that the motor voltage can/should be doubled to drive the coils in series, because else their doubled resistance will result in quarter motor power.
This might work when using full step mode: both coils always have the same current.
It won't work with microstepping when the coils have a different current.
General consensus is that 5 wire motors cannot be used with bipolar drives.
If you have a look at the circuit diagram you see that I CANNOT leave it like it is. After I cut the connection of the two middlepoints and leave the connection of the two halfcoils I have one single coil on each side no matter if the two were symmetric or not. Actually they were, each halfcoil had 20Ohms and now I get 40Ohms for each full coil.
It is true that I now need (or can) drive the motor with double voltage but this doesn´t matter, important is that it works
For full stepping, with both coils activated activated at the same time, it makes no difference whether the cut is made. As already mentioned, and as you can experimentally verify (I have).
