help in chosing from surplus controlers

The boys and I are learning a lot from all of your posts. We would like to build a CNC router and plasma cutter, but are still a bit foggy when it comes to servo controllers. What do we look for when it comes to buying used, commercial equipment?

One vendor says his controllers for brushless servo motors can be used for brushed motors and are good for routers, plasma tables, etc. He has Advanced Motion Controls units, used, and online data sheet has technical infor that we are not too familiar with, as of yet. ( http://www.a-m-c.com/download/b15a.pdf )

Would someone care to advise us on these units? I think that someone familiar with commercial equipment might give some good advice that would carry over to other units often found on the surplus market. Getting comments online would benefit several of us who are getting ready to build.

Please advise ?
thanks
Marc

Hi Marc,

AMC is a trustworthy name. I use their other servo amps for brushed DC motors, and like them.

These amps require an external power supply, too.

These are just the amplifiers, you'll still need a PC software solution for a controller, along with a motion control card, of course.

Hey Marc I saw those amps last night and almost woke up enough to buy now but I kinda wonder about the pwm amps working for brush servos. I couldn't find it on the site he has linked. If you find out please let me know.
turmite

PWM amplifiiers are what I use with my DC brush servos. Nice and cool running.

OK...now we are getting somewhere...having spent years as a teacher on several fronts, I now get to be at a level where I am not even sure if I am able to ask a good question. You all seem to be rather gracious to newbies, so here we go!

Quoting from company literature: "The...PWM servo amplifiers are designed to DRIVE brushless DC motors at a high switching frequency.....They interface with a digital controller or can be used as a stand alone drive. These models requires only a single unregulated DC power supply...."

So, it appears that I mix-fused the terms "amplifier" with "driver" and "motion control card". Here, I was trying to equate these surplus amplifiers with something like a Gecko 320.
Obviously, this is not correct, but I am still not sure when a servo amplifier is needed and when it is not. I don't know enough about the specs that followed the intro paragraph segment quoted above....but, what specs and numbers would we be looking for?

Thanks in advance for further light...I hope I am setting this up so that others can learn as well. I dislike asking the kind of quetions that get asked 12 times a week, but have not found anything clear and concise as of yet for servo lingo...yet an appeal to company literature seems not enough for this newbie....perhaps the ratings for amps is enough to give it away that an amplifier is needed??

Actually Marc they are like the Geckos if I understand the concept.
I just had a return email from art at www.artofcnc.ca confirming the mach2 will output pwm.

turmite

They are not like the gecko's as I don't believe they accept step and direction inputs. They are like the gecko's in that they drive motors.

I personally would go with gecko's. For $114 each, you can't go wrong. Plus they are little.

Brushless motors have 3 wires. How do you run brushed motors with them? Just use two wires?

Roland makes and interface card for drives like that that take step and dir input and have -10 to +10 volt output. Of course a gecko is cheaper than the interface card.

Eric

OK...so we now know that the company is a good company, and the amps themselves are used by at least one person here on his brush motors. Some of us use Gecko drivers (we do in our metal working equipment at home), and one reason we use them is because of price and good reputation...$111 for Geckos are part of the draw, but $20 is an attention getter as well...

What I would like to understand is how do we determine when a servo amplifier is needed? The literature for those amps ( and at $20 each, used, that ain't bad!) says they can be used as stand alone...and there are locations for several motors on each card...

The vendor provided a wealth of material from the company, but newbies like myself are not sure what we look for in the specs, that tells us when a controller card is still needed....some wizards use the term "amp" to mean controller...not helpful, but the literature seemed to indicate they could be used as such...(and the vendor supplied HUNDREDS of pages of support material)

What specs do we look for that tells us when a motor needs an amplifier before the controller? What is it in the specs of an amplifier that tells us it can be used for CNC router/plasma type circuits?

Thanks for all the input...just looking for the kind of info that would enable some of us to NOT have to pester the wizards among you next time a "good deal" comes along in surplus circuits for servo use....

...to amp or not to amp....that is the question...