Tachus Unipolar 3 axis board

[shreifali]

Hi Everybody
I was reading the article about constructing the 3 axis driver board for unipolar , here is the link
http://pminmo.com/3axis/3axis.htm
but I was wondering how this board is for unipolar steppers and it only contains 4 conectors for each motor cuz as I know 4 wires motors are bipolar .

in other words if pminmo has read this message , plz let me know if I can use this board for these motors shown in this thread Bipolar Stepper Motor (Epson)
help plz
thx a lot

[jeffs555]

A unipolar motor has two coils, each with two end connections and a center connection. Sometimes they have 5 wires and the two center connections are internally tied together to the 5th wire. Sometimes they have six wires and the two center connections are brought out on separate wires. Anyway, with the unipolar driver you linked, the 4 motor terminals are for the 4 end connections and the center wires would be connected to the positive supply voltage.

The motors in that thread have 4 wires, so would probably be bipolar and not work with that unipolar driver.

It is however possible to have a 4-wire unipolar motor. In a 4 wire unipolar motor the center connections are internally connected to the metal frame of the motor, so externally the 5th connection would be made to the metal frame. The only way to know would be to measure with an ohm meter. If there is a low resistance between the 4 wires and the metal frame, then it would be a unipolar motor.

[pminmo]

The center tap connection of the motor goes straight to the power supply, there is no connection on the pcb.

[shreifali]

thx for u all for replying
I still have another question :
I opened the motors shown in the link above , no wires connected to the body of the motors. it contains eight coils (windings) . so my question is :
can't we transform this bipolar motor to a unipolar one , by connecting new additional wires from between the coils to the body of the motor.

thx in advance

[pminmo]

If the motor has 8 wires already it works either unipolar or bipolar.

[jeffs555]

You probably mean 8 coil ends and only 4 coils. If the coils are wired in series, then it is just a matter of adding a wire to the center connection of both pairs of coils. If they are wired in parallel, you would have to disconnect them and rewire them in series and then add the wires to the center connections.

[shreifali]

I will send you some pictures of the motor inside , and you will see that it contains eight coils and not four , I mean there are eight windings inside the motor .
but anyway , I would appreciate your help providing me with the schematics of a 3 axis bipolar controller.

[shreifali]

I am sorry , the pictures are not so much clear.
I disassembled those motors from epson and canon printers , and my bad luck they are bipolar . a 3 axis bipolar controller would be the solution .

[jeffs555]

There would be no way to rewire those motors for unipolar use.

Another important point is that it is a very bad idea to disassemble stepper motors that way. The magnets in them lose magnetism when removed so that the motor will lose a significant amount of power.

[shreifali]

thx jeff
but couldn't you provide me with a 3 axis controller to control those motors.
I got exhausted looking over the net for such circuit but in vain.

[pminmo]

There all kinds of free DIY bipolar circuits on my website. You just need to use individual boards and an interface board.

[shreifali]

I chose to use the L297-8 bipolar driver board with DIY 4 axis interface .
did I make the right decision? if yes , please tell me to start the building process.
thank you