Pulling a pin down A4988

Using Arduino Programming Questions
1

Hi,

I am using a A4988 stepper motor driver. I want to use the RST PIN to disable the power output to the stepper if it is not in action.
To do this, you have to pull it down. So I wanted to use a pin of my ESP8266 to do this. Unfortunately It does not work. I pull the pin 13 down but there still seems to be a very low current or voltage what prevents the A4988 board to switch everything off.
If I remove the jumper cable for a short time the board switches to off and I also can put in the jumper cable and the board stays off.
What can I do to achieve this goal?
Do I have to use some resistor somewhere?

greetings

2

Is that a correct use of the RST pin of the A4988 ?
I genuinely don't know

3

Holding a device in reset is a common thing to do when you program a device so I don’t see why you should not do it providing that the voltage on that pin when you release it is not greater than the 3V3 supply and that the current it will draw is within the rating of your pin.

If not you will have to use a transistor (and resistor in the base) to hold the reset low.

The stepping driver will lose the step position which could be a problem especially if you are multi stepping the motor.

4

I am not sure. But i did not get the EN Pin work. And i also did not find any example which shows the wiring and programming of these pins. :frowning:

5

Loosing the position is no problem in my case. Maybe someone else have an Idea how to use RST, sleep and EN correctly :-/
If not, the transistor would be my last choice.

6

Which A4988 module are you using?

7

A Red one

8

Maybe you should try a purple.

9

@crazysky can you post a link to the module you bought please.

10

But that should be the correct way to disable the coil current in standstill. What did you try? And what didn't work? You must drive this pin HIGH to disable the stepper current. If its LOW (or open) the driver will work normally.

11

Sounds like the ol' noob brainlock "HIGH is ON and LOW is OFF".

12

You can get the data sheet here, it will tell you what you have to do the the chip. Note Vdd should be connected to 3V3. In your system.
https://www.allegromicro.com/~/media/Files/Datasheets/A4988-Datasheet.ashx

13

In the case of the enable and reset pins this is true, because the real name is reset bar or ~Reset and Enable bar or ~enable.

14

Hi,

I believe it is the ENABLE BAR that you need to do what you want.

enable
enable738×222 66.9 KB

Tom... :grinning: :+1: :coffee: :australia:

15

Ok guys, I get the EN pin working now. So it's fine for me. I do not know what I did wrong but now it just works.
Thank you very much for your help.
You are great. I was so happy getting so many respones to my questions. Really nice! THanks a lot!

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16

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