Question about multiple motor shields

Hi, I was thinking of using the SainSmart L293D Motor Drivers.

I have about 6 steppers to control, so will need to have about 3 of these brivers.

My question is, can I only attach one board to an Arduino Mega? I was not sure if these drivers need to be mounted on the Arduino board or I can have then not mounted but still work?

See this:

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Thanks for the link. I understand how steppers work and that sort of thing.

I am not sure if my question was clear :)

What I wanted to know was, does the SainSmart L293D Motor Driver shield need to be mounted on top of Arduino board or i can not mount it and still be able to connect in to Arduino with jumper cables.

I asked this because I will be having 3 of these boards to control 6 steppers and they all will not be able to fit on top of a single Arduino board.

I know there is a stackable version available but I am controlling the cost right now for the prototype.

This shield is normally meant to be stuck on top of an Arduino Uno board. If mounted that way it will not be possible to mount a second or third one on top (without having to cut some pins and rewire) as all of them are using the same I/O pins for driving the steppers.

But if you want to wire it via cable - that will give you the freedom to choose what I/O pins you want to use (in the sketch and on the board(s).

You know that you need at least 12 I/O pins to drive 6 steppers?

Before you go on with that approach, make sure that 1. your steppers don't exceed 0.6A each (max. current output of L293D) -> I bet that the L293D will be fried (at continuous 0.6A) if you don't cool them actively. 2. you know that the individual speed of the motors will be pretty lousy (low) - due to the max. voltage and the fact that you want to drive 6 steppers on a 16MHz Arduino

Do you have already thought about using 6x A4988 or DRV8825 instead of the 3x L293D boards? Those stepper drivers can deliver way more current per stepper at pretty high voltages (up to 35..45V) which gives you some better performance and an opportunity to send your steppers to sleep whenever you don't need one of them (cools the steppers down and saves energy).

ssdesign: Hi, I was thinking of using the SainSmart L293D Motor Drivers.

I have about 6 steppers to control, so will need to have about 3 of these brivers.

My question is, can I only attach one board to an Arduino Mega? I was not sure if these drivers need to be mounted on the Arduino board or I can have then not mounted but still work?

You really shouldn't be thinking of using an H-bridge board for controlling steppers.

Most of the steppers you can buy today are bipolar low-impedance, and won't work from such a driver as current-control is mandatory.

DRV8825's, A4988's and other chopper driver modules are cheaply available for handling them, up to about 1.5A or a touch more. These will give pretty decent performance from a 24V supply or higher, will work somewhat slower on 12V supply.

For higher current steppers you will need proper stepper driver units really.

If you have steppers that are high impedance (such as 0.3A, 40 ohm), it is possible to use the L293 and other H-bridge drivers, but you won't get much performance from such a motor (200 rpm or so might be the limit).

Thanks @rpt007 and @MarkT

I am actually going to modify my 28BYJ-48 unipolar motors to Bipolar using the hack I saw on youtube.

Based on your suggestions, I think I will go with these: https://www.amazon.com/gp/product/B01GJJGRF2/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Does this look right?

Well,

going with these steppers is a challenge if you want to get some speed. To give you better and sound advice it would be great if you could tell us a bit more of the goal(s) you want to achieve.

Even by modifying these steppers you will have very very slow speed - they normally come with a gear ratio of 64 which means that you need a lot of pulses to make them move one single turn.

So - what is your project goal and what are your expectations / requirements?

Hi @rpt007 I dont need much speed. I will be making robotic arm that extends and retracts. So most of the time I wont need to do even a full turn.

Those motors have light gears with loads of backlash unfortunately, they won't be very accurate or heard-wearing.

Hi @MarkT Yes, I know these are very light gears. But This is only a 1/2 scale prototype that I am building to test a concept.

If the design works, I will eventually be using VEX 393 Motors to built the final version, which have high torque.

Hi @rpt007 Your suggestion of A4988 was awesome. I ordered 6 of them from Amazon.

This is what I did. I modified my 28BYJ-48 to Bipolar. Used A4988 to drive them.

Now the torque of these motors has increased significantly and they are running from a 9V battery :) Thanks for your suggestion.

You're welcome; make sure that you keep an eye on the current flowing through the drivers/motors. If you don't limit the current flow you might fry your motors on the long run (if you are lucky, your 9V battery limits the current by itself ..).

For more details about adjusting current for A4988 / DRV8825 have a look at my little instruction here: http://forum.arduino.cc/index.php?topic=415724.0