I meant to say no more, no less.

Hi,
Yes, the 0V of the external supply will have to be referenced to the COM of the BoB.

I suspect the that output impedance of the MPG is such that the inputs of the BoB will swamp the 12V A/B outputs down to 5v of the BoB,
Its not very elegant but it should work. Using Zeners and resistors is preferable.

Craig

Okay, we are attached to the common pin directly to the 0V on MPG.

https://youtu.be/hmAn-jH3RqQ

Hi,
having had personal experience with these particular model MPGs, the outputs are 12V/0v. They are both sourcing AND sinking,
ie totem pole outputs, with an output impedance of about 10kOhm.

By all means test the outputs.....but it's not until you hook it up to the BoB that you will know if the outputs have enough current authority to
swing the BoB inputs. Also you won't really know until you try whether you have to limit the outputs to 4.7V or whether the input impedance of
the BoB inputs will 'drag' the incoming 12V down....to....what I wonder?

Craig

Hi,
perfect, you should see the output change every second click...and thats exactly what you see.

In absence of the BoB the output would be 12V, but with the BoB its dragged down to just a little over the BoB supply voltage.
This is not ideal, but it works. You are relying on the output impedance of the A/B outputs AND the input diode clamps of the BoB
to ensure the voltage translation.

When I measured the output impedance of the MPG I did so very quickly.....so I can't be 100% about it being 10kOhm, although I
suspect it would be close. Likewise we cannot be sure of the input diode clamps.....I would guess we are seeing the ESD protection diode of
the buffer IC operating, and most engineers would say that relying on ESD diodes is a bad idea......even if it does work!

Craig.

Hi,
having had personal experience with these particular model MPGs, the outputs are 12V/0v. They are both sourcing AND sinking,
ie totem pole outputs, with an output impedance of about 10kOhm.

By all means test the outputs.....but it's not until you hook it up to the BoB that you will know if the outputs have enough current authority to
swing the BoB inputs. Also you won't really know until you try whether you have to limit the outputs to 4.7V or whether the input impedance of
the BoB inputs will 'drag' the incoming 12V down....to....what I wonder?

Craig

I tested them through the board to motors and it registers on mach3 and moves the motor. Though I can't say if the motor moves correctly due to the high interference in my PCI/parallel ports to know.

As for what the meter says https://youtu.be/hmAn-jH3RqQ

It looks pretty bang on for 5.2V and 0.3V.

The C10 board manual is attached.

I am not sure what the diagrams are, Having never taken an electrical course in my life I'm stuck with YouTube and forums to try and teach myself haha.

Thanks!

Kyle

Hi,
perfect, you should see the output change every second click...and thats exactly what you see.

In absence of the BoB the output would be 12V, but with the BoB its dragged down to just a little over the BoB supply voltage.
This is not ideal, but it works. You are relying on the output impedance of the A/B outputs AND the input diode clamps of the BoB
to ensure the voltage translation.

When I measured the output impedance of the MPG I did so very quickly.....so I can't be 100% about it being 10kOhm, although I
suspect it would be close. Likewise we cannot be sure of the input diode clamps.....I would guess we are seeing the ESD protection diode of
the buffer IC operating, and most engineers would say that relying on ESD diodes is a bad idea......even if it does work!

Craig.

In which case... I should run the A and B through zenners to be sure that the BOB just gets 5V?

There is a few diagrams in the manual with NPN and resistors but they don't specify what it's connected to 🤷‍♂️.

So they don't really mean much to me cause my brain doesn't really connect what's being wired.

Setting up the C10 inputs for pullup and using transistors to buffer the encoder is the surest and safest way to go. If the encoder series output resistance is anywhere near the value Graig suggests no other series resistor would be needed to connect to the base of the transistor.

Hi,
I just pulled my pendant to bits and measured the short circuit current of the output, 1.5mA and an open circuit voltage
of 6.7V

The Thevinin impedance is:
output impedance= 7.7V/1.5mA
=4.66 kOhm

So not 10kOhm, about 1/2 that, 4.7kOhm.....still should not trouble the ESD diodes but if you put a 4.7V Zener across the the BoB inputs...that would be
nice.

Craig

Setting up the C10 inputs for pullup and using transistors to buffer the encoder is the surest and safest way to go. If the encoder series output resistance is anywhere near the value Graig suggests no other series resistor would be needed to connect to the base of the transistor.

Sounds like a plan. Let's roll with it.

What do I need to buy for transistors to buffer The A and B and how do I wire that in?

Would I use an NPN like the attached photo?

And would I use it like the attached drawing?

Or, would I just need to put a Zenner diode on the A and B to regulate the encoder outputs to a 4.7V? (In which case I need a diagram lol)

Thanks,

Kyle

Hi,
I just pulled my pendant to bits and measured the short circuit current of the output, 1.5mA and an open circuit voltage
of 6.7V

The Thevinin impedance is:
output impedance= 7.7V/1.5mA
=4.66 kOhm

So not 10kOhm, about 1/2 that, 4.7kOhm.....still should not trouble the ESD diodes but if you put a 4.7V Zener across the the BoB inputs...that would be
nice.

Craig

Thanks for doing that Craig.

As for the Zener, i will need a wiring diagram dumbed down so I can read it hahahah. Google gives me lots but I don't have a hot clue what gets attached where. Lots show resistors used to?