Dir and Pulse on Grbl_ESP32 CNC Development Board V3.5, Are They 5V or 3V?

[jaysettle]

Wanting to use DM542T stepper drivers with the ESP32 running GRBL. I hope I'm posting these questions in the right area? Forgive me if not.

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?

https://www.amazon.com/gp/product/B06Y5VPSFN/ref=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1

[misan]

Do not forget GND for the ENBL- input.

On Wed, Aug 21, 2019 at 1:25 PM JAY notifications@github.com 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=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1

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[bdring]

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.

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

[jaysettle]

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

[misan]

@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 notifications@github.com 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

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[jaysettle]

I missed that. Good find.