[Grbl_Esp32 Issue#194] Dir and Pulse on Grbl_ESP32 CNC Development Board V3.5, Are They 5V or 3V?

#1 – misan 于 2019-08-21

Do not forget GND for the ENBL- input.

On Wed, Aug 21, 2019 at 1:25 PM JAY wrote:

> Wanting to use DM542T stepper drivers with the ESP32 running GRBL.
>
> 1.
>
> I don’t mind using a PCB if it gets me 5V level shifters for axes and
> spindle and caps for limit switches etc. *Is the Grbl_ESP32 CNC
> Development Board V3.5 the board I should go with?*
> 2.
>
> I’ve found that the spindle pins are level shifted. *Are the Direction
> and Pulse pins level shifted to 5V on the Grbl_ESP32 CNC Development Board
> V3.5?*
> 3.
>
> Looking at the picture below, is this the correct way to wire this
> from the Grbl_ESP32 CNC Development Board V3.5?
> [image: image]
> <https://user-images.githubusercontent.com/603364/63428096-b9e0fb80-c3e4-11e9-8aab-3df6449e5f70.png>
>
> [image: image]
> <https://user-images.githubusercontent.com/603364/63427655-a41f0680-c3e3-11e9-8e4e-6997c43649b1.png>
>
>
> https://www.amazon.com/gp/product/B06Y5VPSFN/ref=ppxyodtbasintitleo05_s01?ie=UTF8&psc=1
>
> —
> You are receiving this because you are subscribed to this thread.
> Reply to this email directly, view it on GitHub
> <https://github.com/bdring/GrblEsp32/issues/194?emailsource=notifications&email_token=AADRZSGPWQM5N4OI63JSF63QFUQX7A5CNFSM4IOFSBN2YY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4HGPQUQA>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AADRZSDGDHGGJRJLPMSJV33QFUQX7ANCNFSM4IOFSBNQ>
> .
>

#2 – bdring 于 2019-08-21

The ESP32 is 3.3V. Those typically use optical isolators. They require 5V (or more with external resistors). They are consume about 10mA of current. I don’t think my Dev Board V3.5 will work.

Many level shifters use a pull up resistor for the high side and therfore cannot supply enough current.

I recently use a similar driver for one axis of my String Art Machine. I used simple transitors to switch the low side (PUL-) and tied the high side (PUL+) directly to 5V. It worked perfectly.

Here is part of that schematic.

!image

I wonder what would happen if the ESP32 tried to directly sink the current on the low side

#3 – jaysettle 于 2019-08-22

It would be great to use an optotransistor here like the EL817 however I’m reading the ESP32 outputs a measly 12mA on GPIO.

This wouldn’t work for the EL817
!image

#4 – misan 于 2019-08-22

@JAY Plus the beefier external drivers already include optoisolators at its
inputs, so adding another optoisolator on the ESP32 outputs would only
increase cost and delay over a bipolar transistor output.

On Thu, Aug 22, 2019 at 5:56 AM JAY wrote:

> It would be great to use an optotransistor here like the EL817 however I’m
> reading the ESP32 outputs a measly 12mA on GPIO.
>
> This wouldn’t work for the EL817
> <http://www.everlight.com/file/ProductFile/EL817.pdf>
> [image: image]
> <https://user-images.githubusercontent.com/603364/63484879-328c9a00-c46f-11e9-8872-958a6f576640.png>
>
> —
> You are receiving this because you commented.
> Reply to this email directly, view it on GitHub
> <https://github.com/bdring/GrblEsp32/issues/194?emailsource=notifications&email_token=AADRZSC2DPW5DVVA3XKC4PTQFYE67A5CNFSM4IOFSBN2YY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD43ZOEI#issuecomment-523736849>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AADRZSGTZ7QVNCKFVPMAUFDQFYE67ANCNFSM4IOFSBNQ>
> .
>

#5 – jaysettle 于 2019-08-22

I missed that. Good find.