Servo power supply sizing?

You have brushed dc servos, you must have encoder feedback for linuxcnc or the machine will never be accurate or repeatable.

A mesa 5i25 and 7i77 with encoders and dc brushed motir drives is precisely what you need to build. The geko drives will require a encoder feedback. Do not trust those drives to accurately position the machine.

If you need elecrtocraft tachometers, i have 4 that might fit off some dead servo motors.

smc.collins wrote:

You have brushed dc servos, you must have encoder feedback for linuxcnc or the machine will never be accurate or repeatable.

A mesa 5i25 and 7i77 with encoders and dc brushed motir drives is precisely what you need to build. The geko drives will require a encoder feedback. Do not trust those drives to accurately position the machine.

If you need elecrtocraft tachometers, i have 4 that might fit off some dead servo motors.
 

Are you in sales or something? I thought i had made it clear that the servos on my techno-isel lc3024 have 1000ppr encoders attached and that i have acquired gecko G320x drives. My servos work fine. This cnc router has seen very little use in the 12 years since it was manufactured -- I just acquired it without the control box. The control box is probably still bolted to a wall somewhere in salt lake city. 

 

TimpanogosSlim wrote:

Are you in sales or something? I thought i had made it clear that the servos on my techno-isel lc3024 have 1000ppr encoders attached 

No need to be rude. People here are donating their time and  just want to help. Sometimes a helper might get something wrong.
Thats the beauty of communications... the only thing clear is the message the recipient gets. And you sent it so thats your responsibility. 

As i have explained, your encoders need to goto the control card, unless you're attempting to foolishly use dc motors in step direction with the gecko drives

Best of kuck, as i have explained, you're building the machine in the wrong way. 

 

rodw wrote:

TimpanogosSlim wrote:

Are you in sales or something? I thought i had made it clear that the servos on my techno-isel lc3024 have 1000ppr encoders attached 

No need to be rude. People here are donating their time and  just want to help. Sometimes a helper might get something wrong.
Thats the beauty of communications... the only thing clear is the message the recipient gets. And you sent it so thats your responsibility. 

Respectfully, the DIY CNC community is lousy with people whose free advice is "Nah, throw away all that stuff and buy this other thing that appeals to me, that I maybe have not ever even seen in person"

I've heard that over and over on this project. Trash the brushed DC servos and get AC servos. Trash the brushed DC servos and get these steppers. Don't use that tried-and-true driver use this other driver that appeals to me in some way. etc. 

And it's not helpful.  

And I'm also a little irritated that so many people have attended the Tim Taylor school of engineering and want to tell me that everything needs to be so much bigger with more power grunt grunt grunt. With no supporting logic. 

smc.collins wrote:

As i have explained, your encoders need to goto the control card, unless you're attempting to foolishly use dc motors in step direction with the gecko drives

Best of kuck, as i have explained, you're building the machine in the wrong way. 


 

The DC320x drivers are explicitly designed for this use case? 

tommylight wrote:

Geckos work well, use those.
And if by any chance the existing encoders do have differential outputs, you can have one side wired to geckos and the other side to Mesa so you can close the loop in LinuxCNC.
Just be aware that gecko and Mesa must have the same ground for the encoder side.
-
I have a huge industrial plasma using geckos, in use daily for over a year, it never shuts down.

That does seem to be the majority opinion. I'm sure that there are pros and cons for various other drivers. 

I'm dipping my toe in. I have no definite plans for commerce - I'm just fucking around. I may try to clone some of the odder soviet guitar bodies. 

So I'm starting small. I paid a bit short of $600 for the router including taxes, etc, and could have just stripped it for parts and sold them for a profit.

I'm starting with a parallel port BOB on an SFF computer I have kicking around. I'm sure there are opportunities for more speed, greater reliability, etc, that come with more money and more complexity. 

And yeah, they are differential output encoders, so I'll be attaching the positive side to the geckos and could connect the negative side to the controller. But I'll worry about that some time after it has moved under its own power. 

I've got enough pieces that i will cobble a temporary servo power supply and start testing stuff in earnest, maybe hook up the scope and function generator and take a look at the damping. 

I've got a large transformer that used to power motors on a c-band dish (with a single bigass diode and no filter caps!), that and a big bridge rectifier and some big caps should provide proof of concept. 

The price difference between 500w and 1kw antek supplies is small enough that I'm resigned to just getting the 1kw supply. And a soft start module.