Motor and controller questions

[sYmbot2]

Hello everyone;
I am working out the mechanical bits for a gantry router that would be my first learning curve into the home CNC hobby. I need advise and information on the following areas please.

I have come across a site called PMinMO and the gentleman there sells PCB's to build controller boards for bipolar motors and interface boards for same.
I had read somewhere that 6wire unipolar motors can be hooked up as bipolar on the controller boards, how is this done? I ask this question because I presently have an Applied Motion product 6 wire motor and would like to purchase two more 6wire motors to use the PCB's I just mentioned.
The next question is, should all motors be of the same rating in terms of volts and amps or could there be variations in ratings of the motors?
In the meantime I am working out the prices for parts to complete these boards versus buying a complete kit form HobbyCNC. The thing I like about building the PMinMO boards is the modularity versus everything on one board as the HobbyCNC kit .
Thank you for all the help you will give me .

Sincerely
sYmbot2(Larry)

[chazmtu]

Hi Larry,

The short answer is yes, you can use six wire steppers as a bipolar motor. Check out this site. The common wires mentioned here are not used. That leaves you with two coils each has its own small driver on a bipolar controller. Bipolar motors are stronger than unipolar but require more complicated hardware.
I own a hobby cnc board and they work pretty nice. They only run your motors as unipolar though. The big cost, imo is the power supply. I'm using some modified pc power supplies as they're free if you know where to look.

Chuck

[chazmtu]

Forgot about the second question. Generally when you have two motors with interpolated motions such as the x and y axis working together you want both motors to have the same number of steps/rev or deg/step. It should be printed on the motor. One point to consider is that two motors with different ratings are going to have different strengths and speeds, so the stronger and or faster motor will be limited by the other.
You would probably be better off with identical motors for the x and y axis and then a separate for the z axis wold not make much difference.

[sYmbot2]

Dear Chazmutu;

Thank you for clearing up the motor and controller questions that I posted.
I have another question.
The board that I plan to puchase from PMinMO is called the L297- 298 board. This controller has a power rating of 46VDC @ 2 amps. The motor I want to choose are either 5V/1.4A per phase or 2.3V/3.0A per phase.
The power supply specs that I am looking at is 36 Volts 2 amps or 2 PC power supply hooked up to produce 24volts @ 8 amps.
Which would be better to use for the motors I want to use and the controller power needs?
Again thank you for the advise you provide.

sYmbot 2(Larry)

[chazmtu]

OK,
The pminmo website says that your board can handle up to a two amp motor so I'd go with the 5V/1.4A per phase motor. Since this board is a chopper drive it will get the best performance with a voltage close to 46VDC but you could get away with 24v or higher. Don't use a supply at 46vdc you want some extra room in case of power spikes. I didn't find what kind of current supply you need but they do have a forum section for power supplies here. If your 36v supply will work then that would be the best. And keep in mind this board supports one motor so you will need 3 of them (one for each axis of movement) and the power supply will have to support all of them.

Finally, this board has a current controller that needs to be set for the motor. These controllers have instructions similar to my hobbycnc board. You might want to set the motor current to 70%-80% of their rated current (1.4A) to keep them from getting too hot. The idea is to sacrifice very little performance for much cooler motors. Maybe they could recommend an optimal value on their forum. I know it sounds involved but It's actually pretty simple once you get started.