Pololu Driver Board Rev 2

[bdring]

While it was pretty easy to get my first generation Pololu board working by moving the laser power supply, it did reveal that the drivers are sensitive to noise. I decided it was better to redo the board to make it more robust to a noisy environment. I also took the opportunity to improve it in a few other areas. Here is the list of changes I did.

• Added a capacitor to Vdd at each driver to fortify the logic voltage to prevent drop outs.
• Added a high speed RC input filter to all step and direction pins. (<1uS)
• Added a Schmitt trigger for each step and direction line for noise suppression.
• Added a pull down to all step and direction pins. In case these are not connected to a controller when powered
• Add RC filtering to all inputs lines for limit switches and spare input.
• Changed laser power supply connector from terminal block to RJ45 shielded connector. A Cat 6 shielded cable is a cheap way to get high quality individually twisted, shielded pairs. It also provides a nice quick disconnect connector.
• Change DC input from terminal block to coaxial jack. Again, a cheap and easy way to get a shielded power cable. connector is rated for 5A.
• Improved labeling of connectors and terminal blocks.

Note: some of the RC values may later change.

Here is the schematic and a screenshot of the artwork. I will clear my brain for a while and give it a fresh look before I buy it.

[tylerv]

This board is looking really good! I've ordered three Pololu drivers and plan on using them with this board once it's ready. In the mean time I'll use a breadboard and play around with a spare stepper I found last night.

Also, do you have a recommended source for the Pololu driver heatsinks (from this post)?

[soehler]

Looks promissing and really nice
I also got pololu drivers and heatsink just waiting for the board.
By the way I got heat sink from Sidewinder @ http://www.sidewindercomputers.com/enmofocomohe.html

Sergio

[bdring]

FYI: Right now as the board is designed, it only supports the newer A4988 as far as full micro stepping options. The A4988 has built in pull down resistors for the microstep selection pins. The A4983 would have some MSx pins floating in all modes except 1/16th step. It would take another 9 resistors on the board to do this. I could use arrays, but since the board is all through hole, it is pretty stuffed already. The A4988 all has over current protection too. I think I will leave it as A4988 only. They are the same price.

[soehler]

Bart

Good to inform people about this

4988's is wat I got.

Sergio

[artwood_decor]

Bart,
It would be good if you link the Pololu board to your Kits and Parts page, as many of us will buy these boards now, so you will get a fraction.
That will pay a very little portion of you time and efforts.

[edmond22]

That board really looks good,cant wait for it to be ready, my steppers are just waiting for it.

[bdring]

I have 9 prototype boards on order from Gold Phoenix. They take 6 days + 3 days shipping. Please do not request any of these prototype units. I will determine what to do with them after testing. Source documents (gerbers) will be posted after testing.

[bdring]

The boards have shipped from China. They are due on Wednesday. I should have them tested by the end of the week.

[J45on]

Looking forward to the results
I'm quite excited about this driver board