Proto Trak MX3 Retrofit - Which Boards Mesa?

Your schematic looks to be correct to me. I now have all 3 Axes functioning using 7i25 and 7i85s Mesa boards. Another thread that has some excellent information on the subject can be found here. forum.linuxcnc.org/forum/38-general-linu...7i85s?start=30#77328

If you have any specific questions regarding my set-up, please feel free to ask.

Thanks,
Jeff

techrat wrote: Your schematic looks to be correct to me. I now have all 3 Axes functioning using 7i25 and 7i85s Mesa boards. Another thread that has some excellent information on the subject can be found here. forum.linuxcnc.org/forum/38-general-linu...7i85s?start=30#77328

If you have any specific questions regarding my set-up, please feel free to ask.

Thanks,
Jeff

Hi techrat
I've read recently your work about the Prototrak conversion, and it is awesome. I was thinking to convert my Bridgeport mill machine too. But to be honest I'm very new in servos control.

I've the same Servo controller that you (20201) and apparently the same motors too.

So I've a lot of questions about that and I would really appreciate your help.

Why you used the "Mesa 7i85s" instead of a simple "brakeoutboard" from ebay?

Can you please upload some pics of your setup configuration? That's really can be helpful.

My initial plan was to purchase a old pc and install LinuxCNC on it. But I have the "Raspberry Pi", so maybe I'll use it. And then connect the breakout board on it and the Servo controllers to the breakout board. But reading your post, I'm not sure that this will be the best way to follow.

Thanks.

P.D.

Sorry for my bad English, I'm studing the language yet.

vsidon wrote: Why you used the "Mesa 7i85s" instead of a simple "brakeoutboard" from ebay?.

The Mesa 7i85 (or, in fact, just about any Mesa card, or any Pico or Genreral Mechatronics board) can read encoder pulses at at least 250kHz and in some cases as much as 10MHz. A parallel port + breakout board (or a Raspberry Pi) has to count encoder pulses in software and so can only really manage 10kHz encoder counting.

Also, you have a very limited number of IO pins with a parallel port, and no easy way to get analogue voltages to control servo drives.

The PWM generation will also be an issue with a parallel port/RasPI implementation

For a step/direction driven system, a parallel port + simple breakout will work fine
as should a RasPI if low enough kernel latency is possible.

The Prototrack hardware is not step/direction and needs multiple channels of differential
15 KHz PWM and has high resolution encoder feedback, neither of which are going
to work well with a parallel port or RasPI GPIO interface

Thanks guys for your feedback.

In this point I'm not sure how to proceed. About the "RasPi" I remember that I used it for my Laser Engraver, so, my best option is to use a PC with LinuxCNC installed
on it.
So, what I suppose to do? I have read the two topics from techrat and Jrjones and replies from you. Jrjones has used an Ethernet interface from MESA and the 7i85s daughterboard, and apparently he needed some additional configuration.
The last thing that I've read is that techrat has used a 7i25 H-Bridge for his project, and this confuses me. So, If he uses the 7i25 I suppose that he no needs the servo amp from prototrak.

I need to do much more researching about how to use the MESA board because I'm in blank. In the past I have used only stepper motors and it's more easy to configure it and I was thinking to purchase 2 NEMA motors and put them instead of the original servos but the torque/horse power relation it worries me.

I've attached a diagram that's how I think it is the connection.
In resume. I just need :

1.- PC - LinuCNC
2.- 5i25 PCI board.
3.- 7i85s Mesa Board
4.- Servo Amp from Prototrak
5.- Original Servo an Encoders.
?

Thank you.

image missing https://dl.dropboxusercontent.com/s/lnb9n2so1kt15ji/Prototrak_To_LinuxCNC.PNG

The diagram looks about right. If your hardware is currently functional then the Jrjones solution is probably best.
You should be able to simply re-use all of his config files as-is of the machines are identical.