Re: Servo controller

["Fred Zinsli" <fred-at-shooter.co.nz>]

Hi Nic

We have found a similar problem with Stepper controllers. whilst there are 
many available, they are not cheap, and are very limited in there current 
capacity, therefore lending themselves to relatively small steppers.

We have almost finished our tests on a 5A/coil, 10A total continuos bi-
directional stepper controller without the use of FETs or BIPOLARs.

It's configuration will be as an individual channel per board with 
half/full step capabilities only. and will be ideally suited to the larger 
frame 34 & 42 types. as this is what we are using on our mill.

I will be advising the list as to when we have finished our testing, and as 
to the release into the public domain of ALL of the design details.

We are also testing our own SMPS (SwitchMode Power Supply) that will take 
110Vac or 220Vac and allow for an adjustable 5-36Vdc -at- 20Adc continuos  
output. This should suit every stepper motor imaginable. And in fact, was 
designed to run several motors as a unit.

I hope this helps anyone who is looking for a large capacity stepper 
controller, and wishes to build there own in order to reduce costs, or to 
customize a design for there own solution.


Regards


Fred

-----Original Message-----
From: "Nic van der Walt" <nic-at-unibell.co.za>
To: Multiple recipients of list <emc-at-nist.gov>
Date: Sun, 19 May 2002 12:47:40 -0400 (EDT)
Subject: Servo controller

> 
> Hi
> 
> I'm rather new to the CNC scene, and after a lot of searching around
> and reading about what is going on the biggest thing that strikes me
> is that there is almost nothing for free when it comes to servo or
> stepper
> drivers. This is a sad situation.
> 
> I have download and looked at Garrett's servo controller schematics.
> I have tried to send him email, but the address in the readme bounced.
> 
> What is the current status of the hardware and drivers for EMC? Has his
> design been tested?
> 
> I need a 3/4 axis servo controller with EMC and I'm willing to
> do the following:
> 
> 1) Change interface from ISA to Printer port. I have done this
> previously,
> and it should be possible to run four sets of DAC's and counters on the
> printer port. I can also add some IO for limit switches and relays.
> 
> 2) Do a PCB layout and put it in the public domain.
> 
> 3) Do some modifications of an existing driver to change from driving
> and ISA card to a parallel port based card. I don't want to get to
> caught
> up in lots of coding though. Starting a driver from scratch is not
> really an option.
> 
> Maybe modifying the servo-to-go driver is a better idea.
> 
> One thing I will need advice on is the best way to drive the servo's.
> The simple
> bridge in the circuit seems ideal, going for PWM is going to add
> mountains
> of complexity and maybe even resonance problems in the motors. The only
> downside I see in linear drive is dissipation, and if the driver is not
> inside the PC that does not matter.
> 
> I will keep this a TTL chip and standard transitor design, so that
> anyone anywhere
> can build it. I want something cheap, simple and not to nasty.
> 
> My expertise is digital electronics and PCB design. If the circuit is
> sound, and the
> driver not to complex I can do this very quickly.
> 
> If someone offers to help with the driver this will go much faster. I
> will post preliminary
> schematics in a couple of days.
> 
> Regards,
> Nic van der Walt
> 



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