SparkFun Forums

[desetland]

So far reading has not come up with the answer. It does state that the boards VCC 5+ can be used to drive other devices up to 50Ma. But is it OK to use that to any of the MS inputs to control micro stepping without running connections to an Arduino ?

[Valen]

If you connect a resistor between the 5 volt and the MS input then it will go to 5 volt also. This is called a pull-up resistor and is usually in the 10k ohm for digital inputs.

https://learn.sparkfun.com/tutorials/pull-up-resistors

[desetland]

Thanks for the reply, let me ask this another way then. How to do a pull up is not the question. Or more like finding the 5+ signal is.
Method 1: MS1 can be connected to a digital output from an Arduino or similar micro controller. A hi or low would be enabled by code.
Method 2: use of a dip switch to select micro stepping values without need to reprogram code.
This is more of what I'm working on. Unlike a Pololu A4988 the BED is getting it's power from the motor supply. It also states that it has a 5+ output on the board. So the question remains, using the 5+ output off the BED and feeding that to any of the MS / reset / sleep inputs via a pull up, would that fry the BED? Or not?

I ask because some devices can not deal with voltage signals coming from it's own internal power supply.

[Ross Robotics]

using the 5+ output off the BED and feeding that to any of the MS / reset / sleep inputs via a pull up, would that fry the BED? Or not?

I ask because some devices can not deal with voltage signals coming from it's own internal power supply.

No. The A4983 does not have an "internal supply." It's supply comes from your voltage source. If you look at the schematic, it's already pulled high through a 20K resistor.

[desetland]

Hmmm. OK, I'll try again as both replies have had nothing to do with the question.

Limiting this question ONLY to the Big Easy Driver. The Big Easy Driver has a 5+ output. Can that be connected to its own MS1 via a 10K resistor to pull hi that pin and enable a different step rate or will it fry the board?

[Ross Robotics]

WHY? It ALREADY has one! IT"S ALREADY PULLED HIGH! You can't pull it even higher..

[Valen]

So, the short answer to the initial question was "yes" after all, it is ok. But as Codlink showed (I didn't look at the schematic, I just jumped the gun to the pull-up answer. My bad.) it is already connected to Vcc via a resistor. Adding one in parallel wouldn't hurt (barely more current consumption) but doesn't help anything either. If you need larger step sizes (and thus quicker speed but rougher motion) then you can pull the MS1 and/or MS2 pins to ground via a switch or directly by wire. By default it is microstepping ( 1/8 ) due to the pull-ups if left unconnected.

The board will NOT be fried, unless you make the mistake of connecting ms1 /MS2 to the power input (8v -30 v). Or disconnect the motors while it is powered.

[desetland]

So, the short answer to the initial question was "yes" after all, it is ok. But as Codlink showed (I didn't look at the schematic, I just jumped the gun to the pull-up answer. My bad.) it is already connected to Vcc via a resistor. Adding one in parallel wouldn't hurt (barely more current consumption) but doesn't help anything either. If you need larger step sizes (and thus quicker speed but rougher motion) then you can pull the MS1 and/or MS2 pins to ground via a switch or directly by wire. By default it is microstepping ( 1/8 ) due to the pull-ups if left unconnected.

The board will NOT be fried, unless you make the mistake of connecting ms1 /MS2 to the power input (8v -30 v). Or disconnect the motors while it is powered.

Thanks! THAT was the info I was looking for!
To be clear, then ALL of the MS pins are pulled up on the Big Easy Driver by default then?
So to change the step value it means connecting the selected pin(s) to ground.
That makes life simple.

[Ross Robotics]

What would have made life simple for all of us would be you asking the correct question. Product page has the schematic to answer your next question.

[desetland]

What would have made life simple for all of us would be you asking the correct question. Product page has the schematic to answer your next question.

There was nothing wrong with the question. Questions come from miss understanding or not understanding information. Valen, thanks for the response and kind clarification.