help-stepper controller v1.1

hello guys,
thanks for the reprap stepper controller.and keeping the design open source.
here my purpose of using stepper controller is moving an object in 2 different directions using ball screws.(not cnc).
so i made the board(using the Gerber file u guys provided).
but before starting i have some doubts in my mind.i'll be using step and direction from computer to control the steppers.
1.can i use this design very regularly? imean how tough it is?
2.can i use UF5408 instead of 5404(as 08 seems much better)
3.what is the method of tuning the current for different motors?
one of my friends said Vref=Imax*Rsense.
so say if i use motor with 4A rating,my Vref(value between TP1 and ground) should be 2 volts.is is right?(with 0.5ohms resistor)
4.if i over drive the stepper(5v stepper with 12v),what shld i change in the circuit? and what shld i get at the tp1 test point.

i already made my PCB's.so i desperately need help guys.
thanks once again.
Regards

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2.can i use UF5408 instead of 5404(as 08 seems much better)

Forgive my ignorance here, but what makes it better? It seems to have much higher voltage tolerances, but are they actually necessary?

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so say if i use motor with 4A rating

...then you'll probably destroy the L298. 2A per phase is the limit of the chip, and you don't want to be running things at their limits because they won't last anywhere near as long. If you mean 4A per phase, then you're out of luck.

If you want to drive bigger motors, there's always [avrstmd.com] which can manage 3A per phase, I do believe. Anything larger than that, and you'll have to roll your own own cough up for a commercial driver.

1. It will be reliable provided you don't exceed 2A and you have a big enough heatsink.

3. You adjust the voltage on vref or alter Rsense. As RU says 4A is way too much and for high currents you are better making Rsense smaller rather than raising vref to avoid wasting power and needing as high wattage resistor.

4. The motor voltage does not matter, the smaller the better. The driver board controls the current, which is what is important.

You can drive a 4A motor as long as you keep the current below 2A. You will get half the torque and four times less temperature rise in the motor. Note the if you run a stepper at its maximum rating continuously it will get very hot indeed and general requires to be mounted on something that will take the heat away. Better to use a motor that is more powerful than you need and under run it to keep it cool.

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[www.hydraraptor.blogspot.com]

Thanks for the reply guru's.
actually in my 2 motors one is rated at 4A and other at 1.5A.
so say if i want to use both of them i have to run the 4A motor at 2.0A(which makes the Vref-1 volt) and 1.5A motor Vref-0.75 volt.
and i'll surely use a big heat sink.

one more thing is bothering me.(iam not very good at steppers stuff).on my motor its written voltage-5V and Amp-4A,this mean 4A per phase or for all the phases.how can i clarify this.is there any formula calculate ?
thanks once again for the response.
Regards

Yes those would be the correct Vref values. Note that the power in the sense resistor is V^2/R, so you need 2W resitors and they will get hot. You might consider using lower value resistors to reduce the dissipation.

Motor currents are stated per phase in my experience. To check you can measure the resistance of a phase and use the Ohm's law: I = V / R.

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[www.hydraraptor.blogspot.com]

hello all,
after waiting for a long time,yesterday i got my PCB and motors.i populated the pcbs,they are working just fine(except one,pcb manufacturing problem).so i connected my 3 motors
rating is 2 motors -4v @0.95A
1 motor - 3.9v @1.3A
so i adjusted the Vref accordingly.0.45v for 2 motors and 0.65 for one motors.these supposed to be the required values.
but what i observed is when i run then on 5v supply they are little hot.(not very hot..but u know kinda warm)
so as iam running the motors at rated voltage and rated current why they are getting hot.is it normal?
and say if i over driver the stepper(12v instead of 5v) will my vref value changes?

*does any one have working single sided pcb layout for stepper controller?if yes pls do share.
thanks once again for ur help.

You should always run the board from 12V regardless of what the motor's rated voltage is. The board will regulate the current to the desired value. It is not over driving and vref does not change. When running from 5V most of the voltage will be lost in the drive so the current will probably not reach the target value. The higher the supply voltage the faster the current reaches its target, so the faster the motor can be driven.

Stepper motors always get very hot if you run them at their maximum ratings without any heatsinking. Quite often the max rating is for a 80C or 100C temperature rise. They are intended to be bolted to a metal frame to take the heat away.

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[www.hydraraptor.blogspot.com]

"Stepper motors always get very hot if you run them at their maximum ratings without any heatsinking. Quite often the max rating is for a 80C or 100C temperature rise. They are intended to be bolted to a metal frame to take the heat away."

thanks for the reply.after reading ur reply i ran my 2 motors at 12v for 1/2hr.and yes both of them get quite hot(unable to touch them).
so say if i run them below the rated current this will solve my heat problem right.at the same time this will effect my torque i guess.so what shld i do.
i need moderate torque with little heat generation(say touchable)
any more solutions for this problem?

Torque is directly proportional to current, but temperature rise is proportion to power, which is proportional to current squared.

That means if you drop the current to say 70% you lose only 30% of your torque but the temperature rise is halved, often bringing it below 60C, which is too hot to touch.

You can also cool them with a CPU heatsink and a fan, a picture here: [hydraraptor.blogspot.com]

Edited 1 time(s). Last edit at 09/01/2008 01:07PM by nophead.

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[www.hydraraptor.blogspot.com]