A4988 As logic controller?

Good day,

I know this is a very abnormal question as most people will buy this module to do the actual stepper driving.

What i bought it for was act just the stepper translator.

I have build a big h-bridge with larger transistors that can support 4A. This H-bridge circuit takes in 4 [0v-5v] inputs (same layout as the motor output on the A4988 ) and it then just “amplifies” the signals with another power supply.

I Dono if that makes sense to any one?

but now my problem is that i didn’t notice the min voltage of 8v of the A4988. So my question is how can i make my say 12v input on the VMOT pin (which will come out as 12v on the 4 motor pins). How . what can i put in between the A4988 motor out puts and the h-bridge to make the 12v go down to 5v (as the transistors base is only 5v) ?

Thanks, And sorry for the silly question, but the answer is fairly vital to me getting my setup running.

So summary of my question, is how can i step the 12v output down to a 5v input?
Will a voltage regulator work? and keep the PWM? Or do i need to put a resistor in?



What you are trying to do generally sounds like a very bad idea. It might be possible, but there are all kinds of complexities to consider, and the questions you are asking make it clear that this kind of project is currently well beyond your level of electronics expertise. I strongly suggest you look for an existing driver that meets your needs rather than trying to construct your own higher-power driver from a mix of parts intended for something else.

For example, if you just want some kind of very basic high-power stepper motor driver, you should consider starting with a pair of appropriate H-bridges controlled directly by something like an Arduino.

- Ben

I have done that already, but now my problem is the g-code interpreter uses the step and direction pins, but then that cannot control the h-bridge its self, ( i need the 4 signal inputs)

This high powered h-bridge is more of a on the side project, just messing around and learning about the circuits etc, and get my electronics expertise up abit, so i am fully aware that it is not what i “should” be doing, this is not for a feasible solution, i would rather just use the A4988 drivers instead as they clearly have every thing i need. I just bought an extra one to play around with on this side project.

My suggestion is to put a microcontroller between your g-code interpreter and your H-bridge, like an Arduino. It can read the step and direction signals from your interpreter and generate the appropriate corresponding signals for your H-bridge. Note that the reason I suggest you use an off-the-shelf H-bridge is because they generally take care of the complicated stuff for you, like making sure there is an appropriate delay between turing off a MOSFET and turning on the other MOSFET on that same leg, and they often provide more convenient interfaces.

- Ben

Oh ok, i see what you mean,

Do you know of any software for an ardruino that would perform that function?
Or would i have to code it?


You would probably need to write at least some of it. I know there is a stepper motor library for the Arduino that might help.

- Ben