Which Mesa board?

Its probably worth recapping my take on Mesa's history as a relative newcomer to Linuxcnc. Initially Mesa came up with PCI and PCIe interfaces that contained two DB25 connectors that were parallel port BOB compatible. But then they added two main boards. The 7i76 (step and direction) and 7i77 (0-10v servos) plus a few other boards for extra IO. These boards introduced industrial 24 volt field power for IO.

So then they released the 7i92 which was an ethernet version of the 5i25 and 6i25 and it accepted the 7i77, 7i76 et al.
The next step was merging the 7i92 and a 7i76 into one board (the 7i76e) This single board has basically everything you need for a step and direction system with a spindle.

Then they released a cheaper 7i96 with limited IO (just enough) but no spindle control (except you could set one stepgen up as a PWM that could control the spindle via another external addon board. It can also be configured to put a MPG on some inputs but in my view its hard to give up the IO pins. The cool thing about the 7i96 Outputs is that they each contain a built in opto isolated relay capable of 2 amps or something. The IO pins are tied to a common pin that can be either +v or -v so it supports either active low or active high just by altering the wiring.

Mesa could not do that with the 7i76e so they released the 7i76eD which has active low IO. For a new machine you would typically choose the original Active high version but the D version is handy when interfacing with an existing machine that uses active low switching. Back when I built my machine the D version did not exist so it was easy to make a decision! You might have active low wiring on your machine but also, you might find a lot of relays you are using are going to be stripped out so maybe it does not matter much which way you go.

So with that history in mind, you can see a choice of the 7i92 only moves you part way along the evolution and the 7i76e or 7i76eD is really the best choice for a machine that uses step and direction drives and has a spindle.

You might also like to review Norbert's 7i76e connection sheet if you have not seen it yet.
forum.linuxcnc.org/27-driver-boards/3191...-sheet?start=0#85072

Clive, very good! The set up I have only uses step and direction DC servo drives on XYZ and a hybrid stepper motor on the 4th axis. Everything is still step and direction. The spindle is just on / off relay.
So I think the 7i76e will be perfect. Just need to check on pull up or down version. I think all my limit and homing proximity switches are NPN. That fact will determine my sinking our sourcing option.

Just clarifying that the 7i76e has its own opto couplers that if are enough to cover my 1/O requirements wont require an additional BOB?

palmac wrote:

Clive, very good! The set up I have only uses step and direction DC servo drives on XYZ and a hybrid stepper motor on the 4th axis. Everything is still step and direction. The spindle is just on / off relay.
So I think the 7i76e will be perfect. Just need to check on pull up or down version. I think all my limit and homing proximity switches are NPN. That fact will determine my sinking our sourcing option.

Just clarifying that the 7i76e has its own opto couplers that if are enough to cover my 1/O requirements wont require an additional BOB?

PNP switches connect directly. NPN's need a pullup resistor, or use a D board

7i76 has 32 ins and 16 outs. need more? use a 7i84 which can connect directly to the 7i76. That gives you 32 more inputs and 16 more outputs.

Ah, Bevins beat me to it.

And yes no other optos required. Just the flyback diode if switching higher loads.

Use 2.2k Ohm 1 W pullups on Non D version.

And there is not really any excuse not to run seperate min and max limits and homing switches with the number of inputs available

bevins wrote:

PNP switches connect directly. PNP's need a pullup resistor, or use a D board

Bevans, I think you mean NPN's need a D board don't you?

rodw wrote:

bevins wrote:

PNP switches connect directly. PNP's need a pullup resistor, or use a D board

Bevans, I think you mean NPN's need a D board don't you?

yeah, thanks for catching that.

These are what I use for the limits and homing an all axis, NPN.nc.
So I need the 7I76ED ?

Thanks.

Unfortunately the 7I76ED only changes the digital outputs
to sinking vs the 7I76Es sourcing output drivers.

The inputs are still sinking and require sourcing drivers
(switches, PNP sensors etc)

A 7I95,7I96, 7I97, 7C80 can use sourcing or sinking drivers
for their inputs. a 7I76E or 7I76ED would need pullup resistors
to interface with sinking (NPN type) sensors.

Oh now I'm confused
My servo drives are fairly new Chinese drives, step and direction for DC servo motors. My sensors are all NPN. Im currently running Mach4 with Ethernet smooth stepper and BOB. I want to gut all this for Linuxcnc and and use the 7i76e in place of both the ESS and the current 5v BOB.

So with all this in mind is it the 7i76e or ed? I dont mind changing stuff around.

So its looking more like the regular 7i76e and then using pull-up resistors to accommodate all my NPN limit / homing switch inputs. Yes?