Using a Higher torque motor on Driver Board not rated for that motor.

[Sterob]

Gents,
Hypothetical question for you.....
A home built CNC Router was fitted with a much heavier spindle and it started missing steps.
The Router uses a 'all-in-one ' driver board, so the steppers are wired directly to the Board.
The steppers are already the maximum current the board can supply.

Can a separate , Higher Current Rated Motor Driver Board be driven from the existing 'all-in-one' board, just for that one axis?

ie Fit a higher torque motor to the Z axis and use a matching Single Driver board to control it?

Does the 'all-in-one' board need to have that feature or can you just reduce the motor current down, to use to the control the New Driver?
Or does the 'all-in-one' board need to have a specific output in order to drive a External motor controller?

Just spitballing....

Steve

[Sterob]

I have done some reading of a couple of motor driver data sheets and they both seem to say it will work ok ,if you use the correct resistor in series with the control signals to limit the current to about 10mA.
I guess no one has done this?
Bigger Stepper driver.JPG
Steve

[pippin88]

Steve,

The answer is that it depends.

What is the 'all in one' that you have?

You can often find and piggyback the step and direction signals and feed them to a separate stepper driver.

You will not need resistors generally - not sure where that comes from.

The other option is mechanical - a gas spring, constant force spring, air cylinder, or counter weight.

[Sterob]

Did you see the email Nick?

Sent from my SM-G920I using Tapatalk

[pippin88]

Steve,
Got your email

The ebay stepper you linked in your email does not add up. It states in the title 425oz-in, yet in the description 0.8N.m. 0.8N.m is 113oz-in. (approx 141oz-in to the newton metre). I suspect the 0.8 is a typo.
The 387oz-in steppers from Peter Homann are excellent motors. They are about the best fit for most hobby machines. (https://www.homanndesigns.com/index....vers3cauqgcs63)
Note that maximum torque is not the correct way to select a stepper, as they are rated at zero rpm. Larger / "more powerful" steppers usually have worse performance at higher speeds. Inductance is also important.

The 23H276-28-4B stepper is a 270oz-in stepper. That is a reasonable size stepper. There are not many DIY Routers that require more than this. For reference, I use 387oz-in steppers and can rapid my machine around at 20 metres per minute, and it's a bit heavy steel machine.

Got any pictures of the actual machine?

Has the current limit for the axis been appropriately adjusted as described on Page 4 of the manual you sent? (Should be 5V between TP2 and ground to get the 2.5amp max the board will supply).

What is the acceleration set to? That may need to be lowered.

The Mechatronics board maximum voltage of 24V will limit higher speed torque, but will not affect lower speeds.

If it really is needed to use a higher rated driver, you could either solder wires on to the bottom of the Mechantronics board parallel port (e.g. pins 8 and 9 for A axis), or get a "DB25 Male / Female Header Breakout Board".
Or add a second parallel port (PCI card) - allowing additional inputs and outputs.

A mechanical solution may be best.