Basic Mesa 7i76e Wiring Question

Hi Guys,

I am just double checking my wiring for my Gecko 302X servo drives to my Mesa 7i76e,

I have a diagram I got from my supplier and it shows Encoder GND on the drive going to VField 0V (TB1-8) on the Mesa 7i76e and 5VDC from the Error/Reset terminal to a VField Input on the Mesa.

Am I right in thinking that if I am to apply 5VDC power to a input on the 7i76e from a external source the 0V must go through the common (TB-1) on the Mesa board?

the 7i76e
provides 5V/Gnd for etch Steper
so why dont you use this for your encoder
no need to external Volt at all

and YES Gnd must be bridged if you use external

pl7i92 wrote:

the 7i76e
provides 5V/Gnd for etch Steper
so why dont you use this for your encoder
no need to external Volt at all

and YES Gnd must be bridged if you use external

The servo drive has its own supply for the encoder so I will use that to simplify the wiring going from the Mesa,

When you say bridge the ground, Will I connect the Encoder 0V to the 0V of the power supply powering the 7i76e?

Stefan,I 'm a bit out of my depth with servos but something does not sound right. The 7i76e only has one encoder input which you are using for your THCAD.

But the step/dir docs www.geckodrive.com/amfile/file/download/...id/17/product_id/21/ indicate to me that you should connect the common to +5 volts on the stepgen

The STEP and DIRECTION inputs are pull-up loads when COMMON is connected to controller +5VDC.

I would not compromise the 7I76E's 12/24V field I/O by forcing it to run on 5V just to
service the Geckos rather weird 5V bidirectional error/reset circuitry.

Better would be to use spare 5V I/O like a unused step or direction output for reset and
a spare encoder input (say index) for Error sensing. The bidirectional nature of the pin
means you need an open collector type output. You can create this from a spare
step/dir output by adding a either a Schottky diode (Cathode to step/dir pin), an
optocoupler, or a transistor. This circuitry can be common for all axis.

rodw wrote:

Stefan,I 'm a bit out of my depth with servos but something does not sound right. The 7i76e only has one encoder input which you are using for your THCAD.

But the step/dir docs www.geckodrive.com/amfile/file/download/...id/17/product_id/21/ indicate to me that you should connect the common to +5 volts on the stepgen

The STEP and DIRECTION inputs are pull-up loads when COMMON is connected to controller +5VDC.

Thanks for that Rod,

The terminal I am inquiring about it terminal 5 which is the Error/Reset pin,

For some reason Gecko made this pin a input and a output, Meaning that to pull the drive out of a fault you have to apply 5DVC to the pin. At the same time to turn power off to the drives you have to ground the pin.

Its really a pain in the ass to get sorted, I spoke the the supplier who drew up a diagram for me but its just so out of the ordinary for me I am having second thoughts about it being right.

PCW wrote:

I would not compromise the 7I76E's 12/24V field I/O by forcing it to run on 5V just to
service the Geckos rather weird 5V bidirectional error/reset circuitry.

Better would be to use spare 5V I/O like a unused step or direction output for reset and
a spare encoder input (say index) for Error sensing. The bidirectional nature of the pin
means you need an open collector type output. You can create this from a spare
step/dir output by adding a either a Schottky diode (Cathode to step/dir pin), an
optocoupler, or a transistor. This circuitry can be common for all axis.

Thanks PCW,

What is the worst that could happen having one input powered by 5VDC? The rest of the system is running 24VDC,

I was very unsure of the wiring but I contacted the supplier who drew up a diagram for me which I will attach to this post.

Ahh The error/reset pin needs to be pulled high to reset

The issue is that you would need to have 5V field power for the 5V input signal to be recognized
instead of a more reasonable (and noise immune) 24V

What I would do is this:



which allows software to monitor and reset of the error signal

The only thing that might be an issue here is if the 2K pullup on the encoder input would cause a reset

PCW wrote:

Ahh The error/reset pin needs to be pulled high to reset

The issue is that you would need to have 5V field power for the 5V input signal to be recognized
instead of a more reasonable (and noise immune) 24V

What I would do is this:

which allows software to monitor and reset of the error signal

The only thing that might be an issue here is if the 2K pullup on the encoder input would cause a reset

Thanks PCW,

How do I go wiring that up to my 7i76e,

I take it that ENC INDEX IN will go to TB3-10 (ENCB+)

Are all schottky diode similar in spec or do you recommend a certain spec.

And what does SPARE S/D OUT mean?

Thank you for your help

Also I am using the encoder input for my plasma THCAD-10 card.

Is there anything else I can do?

What if I was to use a relay that is trigger by 5VDC to switch 24VDC to the input? Would that be a simple solution that would work?