Questions about steppers and drivers

Questions, Suggestions, Tips, Etc

Pololu A4988

Postby bdring » Thu Mar 31, 2011 1:21 am

I got some Pololu A4988s stepper drivers in the mail today. They ran great. I have not hooked them up to the laser yet, but they ran really smoothly with zero motor noise when stopped. I was surprised how fast I could get the motors to run with no load. That is usually a good sign.

The things are tiny, like smaller than a quarter. I have some heatsinks on order, but I ran it for 20 minutes without thermal cutout at 1amp. & 24V.

Here is my test setup. The linear regulator at the right is for the 5V. All you need is motor voltage, 5V, GND, step and direction to fire it up. It also has pins for microstepping, and disable. It has the tiniest pot I have ever seen to set the current.



snap28.jpg

0J1418.600.jpg
0J1418.600.jpg (62.6 KiB) Viewed 17773 times
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Re: Pololu A4988

Postby whmeade10 » Thu Mar 31, 2011 3:22 am

bdring wrote:I got some Pololu A4988s stepper drivers in the mail today. They ran great. I have not hooked them up to the laser yet, but they ran really smoothly with zero motor noise when stopped. I was surprised how fast I could get the motors to run with no load. That is usually a good sign.

The things are tiny, like smaller than a quarter. I have some heatsinks on order, but I ran it for 20 minutes without thermal cutout at 1amp. & 24V.

Here is my test setup. The linear regulator at the right is for the 5V. All you need is motor voltage, 5V, GND, step and direction to fire it up. It also has pins for microstepping, and disable. It has the tiniest pot I have ever seen to set the current.



snap28.jpg

0J1418.600.jpg


I am new to this laser driver info, but does this little guy do the same thing as the KL- 4020 drivers I plan on ordering. If it does, it would be great to incorporated them into your laser interface board.

Cheers,
Bill
FSE 45w Deluxe CO2 Laser 5th Gen w/X7 DSP | CorelDRAW X7
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Re: Questions about steppers and drivers

Postby r691175002 » Thu Mar 31, 2011 4:43 am

If I had been aware of these drivers before I started my build I would have used the pololu instead of 4020s.

The specs are just what we need, they are less than a third of the cost and they are compatible with 3.3v 1us logic. Literally perfect.
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More on Pololu

Postby bdring » Fri Apr 01, 2011 1:37 am

I got some heatsinks for the Pololu stepper drivers today. Just like the drivers, they are really small. They cost about $10 for 10 pieces.

enzo_hs.JPG


I am playing with a board design. The driver chip uses 3 pins in a binary coded fashion to select the microstep level. I thought it would be cool to have an easy way to externally change this. The board shown below uses coded rotary dip switches to select the microstepping (blue/white lower left). 0 would be full step, then each clockwise click would double that 1/2, 1/4, 1/8, 1/16. The connector and switches could protrude through the skin of the chassis.

Untitled Project 39.jpg
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Re: Questions about steppers and drivers

Postby whmeade10 » Fri Apr 01, 2011 2:04 am

Bart, would this board actually replace your interface board or be an addition to it?

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Re: Questions about steppers and drivers

Postby thechoochman528 » Fri Apr 01, 2011 2:17 am

I was going to create a board to use pololu steppers... but again you have beat me to it.

:P
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Re: Questions about steppers and drivers

Postby bdring » Fri Apr 01, 2011 2:53 am

Bart, would this board actually replace your interface board or be an addition to it?


As shown, it would be a replacement for the laser interface board and the stepper drivers. It would be lower power alternative to the current interface board and dedicated stepper drivers. It will take a week or two before I will even order the raw board. I want to find some low cost plugin terminal blocks that are a little smaller than the ones shown.
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Re: Questions about steppers and drivers

Postby bdring » Sat Apr 02, 2011 3:51 pm

Attached is the proposed schematic. The only new feature is 2 drivers for external relays. I have always wanted digital control of the assist air pump and exhaust blower. This will drive standard 24v relays. It will support an on board 5V or 24v fan.

If anyone notices an error or has suggestions, please let me know.
Attachments
pololu_intfc.pdf
Pololu Drive / Interface PCB
(40.19 KiB) Downloaded 867 times
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Re: Questions about steppers and drivers

Postby J45on » Sat Apr 02, 2011 4:27 pm

What would be the compatibility between this and the RetinaEngrave/Lightobject controllers ?
Is this just a planned update for the Laser Interface PCB ?

Please forgive my laser noob question :oops:
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Re: Questions about steppers and drivers

Postby bdring » Sat Apr 02, 2011 4:37 pm

Same level of compatibility at the PCB level and probably more compatible at the stepper driver level. They are 3.3V compatible and require a short 1uS step pulse. The pinout is designed around the FSE pinout. These are pretty low power drivers, I would not use on a larger laser than the 2.x.
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