Help With Powering/Wiring of a CNC-Style Setup

[coltons]

Hi there,

I've been researching for a couple weeks and this is my setup:

• Arduino Mega2560
  Adafruit Motorshield V2 https://learn.adafruit.com/adafruit-mot ... o/overview
  12V 1.3A Stepper Motor http://www.amazon.com/57oz--NEMA-Steppe ... ch+nema+17
  12V 1.68A Stepper Motor http://openbuildspartstore.com/nema-17-stepper-motor/
  One LED
  One PixyCMU5 Camera http://www.cmucam.org/projects/cmucam5/documents
  One 6 or 12V RC Servo (Not sure which one to choose) http://store.firgelli.com/category_s/1821.htm

My questions are,
1) what should my power supply be if I want to power the Stepper Motors and RC Servo from the Shield (with a separate power supply) and the camera and Arduino through USB?
2)How much current/voltage should I be supplying?
3) Can I safely run the 6V servo on the Motorshield even if it had a 12V power supply?
4) Should I get heat sinks and where should I put them?

I'm new to Arduino but I'm building this for a project for work. Any help would be incredibly appreciated.

setup.jpeg (613.97 KiB) Viewed 571 times

[adafruit_support_bill]

12V 1.68A Stepper Motor

This is not compatible with the V2 motor shield. You have to go by the continuous current rating when driving steppers:
https://learn.adafruit.com/all-about-st ... he-stepper

1) - Since there is a 12v option for the servos, I'd go with that for compatibility with the steppers.
2) - Add up the total amperage of all motors & servos (note that you need to double the 'per phase' current rating of the steppers because 2 phases are energized at a time in most stepping modes). I usually like to size my power supplies with at least a 10-20% safety factor over and above the motor requirements.
3) No.
4) Heat sinks on the 2 H-bridge chips on the shield are a good idea if you will be running close to the rated current limit (1.2A).

[coltons]

Thanks for the quick response Bill!

1) You mentioned the 1.68A motor won't work - is the 1.3A motor compatible with the shield? Isn't that over the 1.2A current limit too?
My main concern is I want to maximize the torque of the steppers without damaging the hardware.

2) With the two steppers (2.6A each) and 12V servo (200 mA), I have a 5.4A total amperage. Would this power supply suffice for my setup then (12V 6A):
http://www.amazon.com/HiMart-Switching- ... +DC+12V+6A

3) If any, what specific heat sinks would you recommend for my setup? My program will be running for many hours

I will be going with a 12V servo for consistency, thanks for the input!

Thanks so much, you're a lifesaver.

[adafruit_support_bill]

1) Both of those motors are too much for the shield. Unlike DC motors, steppers draw the maximum current when they are not moving, so you have to keep the per-phase current rating under the continuous current rating of the shield.

2) 6A should be adequate.

3) This is a good match for the motor shield: https://www.adafruit.com/product/1041

[coltons]

What stepper motors would you recommend that could both be driven by the shield?

[adafruit_support_bill]

These motors work well with the shield: https://www.adafruit.com/product/324
But if you are looking for maximum torque, you should look for 12v motors with closer to a 1.2A/phase rating.

Another option for more torque would be to use the Gshield: https://www.adafruit.com/product/1750
This shield has current limiting, so it can get the most out of the motors. This guide explains how 'chopper' drives work: https://learn.adafruit.com/all-about-st ... he-stepper

[toby]

I'd like to use the V2 Adafruit motor driver shield but need more torque than the stepper you carry. Would this stepper work? It's rated at 1.2A at 4V. The 4V part confuses me a bit though. I was thinking of running this at 9 or 12v. https://www.pololu.com/product/1200

[adafruit_support_bill]

That motor is designed for use with a constant-current driver like the Synthetos gSheild.
http://www.adafruit.com/product/1750

A constant current driver lets you use a higher drive voltage for maximum torque, but limits the maximum current to protect the motor. If you configure the driver for a 1.2A limit, the 'holding torque' voltage when the motor is not moving will be 4v.

https://learn.adafruit.com/all-about-st ... -a-stepper

[toby]

Ahhh, ok. I'm starting to get a grasp on this then. I'm new to steppers so excuse my freshman questions.
It looks like something like this stepper motor would be fine then correct? It's 12v, .4A and has a little more torque than the one I bought from Adafruit (9oz's more at 37oz.in).

http://www.omc-stepperonline.com/nema-1 ... p-166.html

[adafruit_support_bill]

Yes. That one should work fine with the V2 motor shield.