New to MESA

While I am here I also wanted to double check the power connections to the 7i76. As I understand it FIELD power is for 24V for things like LED's, proxy sensors etc that I have around the the machine and VIN power is the 5V to power the board and supply power to the stepper drivers etc.

I intend to power the 7i76 separately from the 5i25 as I already have that in the control box for the now replaced ethernet Smoothstepper I had when running Mach3.

Oh and I just checked how my package with the boards in it is doing and have to wonder about USPS. The package left Chicago and went to Dubai and has just left there. I always thought Australia was the other direction...hopefully the posty guys know it is Australia and not Austria

I'm not sure that VIN is what supplies 5 volt to the logic side. The manual says to use TB3. Just set the jumper to tie VIN to field power. I'm guessing that external 5V is via pins 21-24 on TB3.

I think I'd keep it simple and just take 5 volts from your 5i25. On my 7i76e (which has two expansion connectors like your 5i25), it has a separate 5 volt input and I used. I since found out that I wasted my money as its really only needed if you add expansion boards with high current draw and it can supply the 5 volt from a onboard 5v regulator (to replace the 5v feature of your 5i25).

One thing to check with PCW when you get to install your MPG is that becasue I was using an external power supply, I had to tie the 24V and 5 V earths together to get the encoder to work. I think he mentioned this broke the power supply isolation so the better way would be to use a 5V buck step down power supply attached to field power to retain isolation.

See what he has to say, maybe on a separate thread.

Thanks Rod

To be honest the whole power thing on the Mesa boards has me somewhat confused. In my current setup all the 24V volt power goes directly to each item that requires it and those items just trip the inputs on the PMDX126 to do what they need to do. The only instance where I needed to connect the 24V ground to the 126 was with my BD679 flasher that I built, aside from that 24V goes nowhere near the 126.

Is connecting the 24V supply to the 7i76 first a way of reducing wiring within the control box or something else? If that the case I will have to fully rewire mine to conform to the 7i76 way of doing things. If there is another reason I would love to know why....

Because the only thing I've ever done with CNC is with Mesa, I probably can't help much but here goes.

Forget the parallel port boards for now. What you have on its way to you is an industrial class control that can use 8-32 volt for field power on its inputs and outputs. Most of us run 24 volt power to the board. The advantage of this is that you are far much less suscesptible to noise. But the 7i76 retains 5 volts for step and direction and the logic circuits back to the 5i25.

I don't know about your PMDX but the BOB I've played with uses active low signalling and my 7i76e doesn't. It will make more sense when you get your hardware powered up and can see the pins using halshow but each output also has an inverted NOT signal and you can choose in hal if you want to use an inverted signal with a simple text edit.

I don't know if this helps much but here is how I've wired up my board using a couple of Jaycar BUS bars. One for +24V on the left and the other for -24V on the right. These are connected to Field power.



You can see I have not used many earths and basically only use this if I have a relay or prox sensor on the IO somewhere.

The only 5 volt stuff I have is my Pendant, the Mesa THCAD board to the left of the 7i76e and the relay I added yesterday you can just see at lower left for drive enable. The relay is turned on and off by a take a 24 volt output and switches 5 volts that goes to the stepper controller disable inputs. You will find there are a few places on the Mesa board you can steal 5 volt power from. You've got 5 stepgens and you are probably not going to use their power outputs (I don't). So each of my 5 volt bits is powerd from +5V/-5V on a stepgen. This means I have not needed to add any bus bars on the 5 volt side.

You can see a DB9 break out and plug beside the BUS bars and I've used this to run 24V power up onto my gantry and the 7 limit switches up there on another breakout board I made. Eventually this will migrate to the outside of the case.

So if I want to add a simple mechanical microswitch to an input all I need to do is loop +24 v from the bus bar through the switch and connect the other end to the Mesa input. I use halshow to make sure I have got it right and then do the hal config.

So you are going to throw away your smooth stepper and PMDX board and replace it with Mesa. As stated by Andy, you can also throw away your relay board as the protection and isolation is built in on the Mesa side.

Also remember you will have many more I./O pins so you can use separate home and limit switches on each axis. I've got one shared home/limit switch and its not as nice to configure as separated home and limits.

I think there is a utility that can import your mach config but I've basically done all my config hand editing hal and ini files once I got a roughly working config from pncconf.

Hope that helps.

There is a 5volt terminal specifically for 5 volt logic the 7i76 needs.
Seperate to that is the field power connector (orange terminal strip).
Leaving the default jumper, whatever you put on vin and ground will be for your field power. Re: inputs and outputs.
If you place the jumper to the right, you can provide vin a voltage (8 -32v), and a different voltage for the field output.
So you can supply three different voltages to the 7i76 if you like.

Thank you guys, really helpful. I am about to install the 5i25 as I received the cards today and then I'll be able to visually see whats available to me!