[billy]

Hello,

This is my first post on CNCZONE so first of all thanks for all the ideas/photos that the members of CNCZONE are sharing

I have started a CNC project together with a friend, based on a CAMTECH RM25 machine. The machine had NO electronics at all. Only the stepper drivers.

Since the machine arrived the following problems came out:
1) We are located in Greece = shipping from USA is expensive
2) We don't know if the mechanics of the RM25 has any problems = we cannot invest on controller/boards and power supplies, without knowing that it works

So we decided that we should go the DIY way.

Based on ideas around the cnczone, i have created a small parallel port driver - breakout port.

The board is not here to compete the boards from manufactures, it is a cheap solution (well not exactly a solution) which can be etch at home since it is single side (with about 10 jumbers) and with materials found on your/our local electronics shop.

The board has the following characteristics
1) Buffered output/input for the DB25
pins 1,2-9, 14,16,16 are outputs
pins 10,11,12,13,15 are inputs
and all the signals are going to the end of the board through connectors.
2) On board power supply of the 5V, or 5V through a connector

The board is NOT optoisolated, and the question is:
Should the board be optoisolated or you think that if the stepper motor driver is already optoisolated we don't need an extra layer of security ?

What do you think it should be added on the board based on your experience ?

Is something that we will need in the future that we should be aware now ?

The AVR based stepper driver will come in a second post

Thanks in advance,

Bill

[rokag3]

hello,
the stepper drive and the motor can you give some picture?
If you are in athens I have everything to build a power supply from 12V 50A to 180V 20A dc
about controller board you can work directly with the parallele port and a cheap breakboard or even make one just for one axe
Please do not speak to me in greek i am french living in athens for 13 years and i do not understand greek

[krazatchu]

I've never seen a BOB with buffers on it, but I haven't really seen that many BOBs...

If the driver's have there own isolation, then you prolly don't need it on the BOB...
However, it's always nice to have some isolation for inputs (limit switches, etc)...

You could also add a charge pump circuit, I think there is one floating around on the MACH3 website... It uses a 4538...

You can find a bunch of examples here: http://pminmo.com/

A common opto-iso would be the HCPL2630...
Careful where you run the supply voltage to... I've seen a few cases where they were used incorrectly such that there was no isolation because of supply voltage sharing...
I think the best implementation is to take the power off a USB connector to power the pc side of the opto isolators...

Ciao!

[billy]

hello,
the stepper drive and the motor can you give some picture?

I will upload them when i am back at home

If you are in athens I have everything to build a power supply from 12V 50A to 180V 20A dc
about controller board you can work directly with the parallele port and a cheap breakboard or even make one just for one axe
Please do not speak to me in greek i am french living in athens for 13 years and i do not understand greek

Great .

I've never seen a BOB with buffers on it, but I haven't really seen that many BOBs...

If the driver's have there own isolation, then you prolly don't need it on the BOB...
However, it's always nice to have some isolation for inputs (limit switches, etc)...

You could also add a charge pump circuit, I think there is one floating around on the MACH3 website... It uses a 4538...

You can find a bunch of examples here: http://pminmo.com/

A common opto-iso would be the HCPL2630...
Careful where you run the supply voltage to... I've seen a few cases where they were used incorrectly such that there was no isolation because of supply voltage sharing...

Thanks for the comments krazatchu.

I thought that adding simple 4N26 will do the trick. I will check for the HCPL2630 in my local eletronics shop.

Regarding the isolation on the limit switches.

When you close the switch you want 5V as input or 0 V ? What is the most common ?

I think the best implementation is to take the power off a USB connector to power the pc side of the opto isolators...

Isn't is a bit risky ???

[rokag3]

I think the best implementation is to take the power off a USB connector to power the pc side of the opto isolators...

Isn't is a bit risky ???

no but you must not share the ground on the board

[rokag3]

those steppers are MAE 1.8 DEG .95 ohms /phase 3A/phase
must be driven by a gecko with 75V minimum to have a corect torque at high speed but can be use for test purpose.
despite all controversy i consider servo a much better and cheaper choice

[krazatchu]

To add to rokag3's comment...

It's not risky at all, you already have the parallel port connected to the pc...
And where else would you get an isolated supply for the opto's....
Another trafo/psu is a bit inconvenient...

The 4n26 may work, just check the data sheet for the speed... The hcpl 2630 is a bit expensive at a few dollars each...

The USB port can source at least 100ma @ 5vdc perhaps more, you could find that on wikipedia...

Also, very good point about the grounds.... I made that same mistake on a BOB not so long ago... I ended up cutting the ground plane with a knife to break it up...
Not pretty but it worked...

[rokag3]

hey bill,
call me i am in team with a very good machinist who is making a retrofit of a lagun mill (1,5 tons) using home made roller screw but unfortunately he do not speak english also your machine despite his price is suffering of insufficient rigidity so making a team might be interisting
we have tig ac/dc plasma mill lathe oscillo servo and due to the ecomomic slowdown time me i work only sat/sunday