Connecting 10 Stepper Motors to the Pi

[christaHH]

Hi all!
I am 2 days into using my new Raspberry Pi B+ so forgive me if I sound like an "electronics greenhorn" with big ideas :). However, I have been a software developer for almost 2 decades so not green in the programming world.

Anyhow, I want to connect (and program) 10 stepper motors to the Pi. Up to 9 of them will need to run simultaneously. They don't need to be lightening fast and only rotate 15-30 degrees (haven't actually figured that part out exactly yet) at one time and turning an ultra lightweight disc (thin plexiglass, 4" diameter)

I was going to get these awesome kits - would these be appropriate? I would also have to get some stacking headers as well since it looks like I would need 5 of these (2 stepper motors per HAT). Kinda pricey but seems necessary? Or is there another kit for less $$ that accomplishes the same thing?
http://www.adafruit.com/products/2348

And what kind of stepper motors would you recommend? The smaller the better as space could be an issue :).

And last but not least, it seems that there is a concern with providing power for these 10 motors....without having 10 battery packs (1 attached to each motor) hanging around, is there something or some kit that I can use to provide power for all of these motors (or per HAT)? Or will the out-of-the-box 5V DC power cord powering the Pi be sufficient enough?

Any other words of advice :)? Thanks in advance!! Can't wait to get going on this rad project :)!

[adafruit_support_mike]

How much positional accuracy do you need from the motors?

We have steppers for automotive gauges that will give you really good positioning: https://www.adafruit.com/products/2424 but we also have servos that are much smaller, and much easier to control: https://www.adafruit.com/products/2201

If you can live with the servos, we have a 16-channel servo controller that's just made for this kind of job: https://www.adafruit.com/products/815

[christaHH]

Perfect- thanks so much :)!

[christaHH]

One thing. Probably the dumbest question ever. But can you point me to the page where I buy the black and red wire shown here: https://learn.adafruit.com/assets/22676

I'm following your lessons and slowly learning here :). Thx!

[adafruit_support_mike]

Not a dumb question at all.. there are some details about that particular connection that you probably weren't born knowing. ;-)

We use 22 gauge solid-core for motor power because it provides a nice balance between size and current capacity:

https://www.adafruit.com/products/288
https://www.adafruit.com/products/290

We also have a six-color set, because it's never too early to learn the habit of color-coding your wiring:

https://www.adafruit.com/products/1311

In general, the more current you need to move, the thicker you want the wire to be. The resistance of the copper (and the heat generated as current flows through it) is the limiting factor on what wire to use. Even the smallest wires can carry signals that only move a few milliamps. When you get up around 1A, you want to use 20 gauge or thicker.

Wire diameter doubles every 6 AWG numbers, and I use 30 gauge as my reference point: its diameter is 0.010". 24 gauge is 0.020", 18 gauge is 0.040", and 12 gauge is 0.080".

Doubling the diameter gives you four times as much copper, so the wire can carry four times as much current. I set the limit of 30 gauge at 250mA, 24 gauge at 1A, 18 gauge at 4A, and 12 gauge at 16A.

For the in-between gauges, each size can carry about 80% as much current as the next thicker number, and 25% more current than the next thinner number. 22 gauge can be trusted to carry about 2.5A, which is a good ballpark for small motor power.

[Dunks]

I'd like to piggy off this post if you dont mind...

I have a raspberry pi3 and i bought the "Adafruit DC & Stepper Motor HAT for Raspberry Pi - Mini Kit" with intention to run one stepper motor and reading information in from an IR sensor. But since this hat takes up all the GPIO pins, does that mean i can't add any other sensors to it?

- Duncan.

[adafruit_support_bill]

The HAT does not take up all the GPIO pins. It only uses SDA and SCL. The SDA an SCL pins can be shared with other i2c devices. The other GPIO pins are all available for use. You can access them via the breakout holes next to the headers, or build the HAT using stacking headers. https://www.adafruit.com/products/2223

[Dunks]

Fantastic, thank you very much!