“This ‘ible describes an integrated unit of
CNC motion controller,
controller power,
switched and fused motor power,
ABORT/HOLD/RESUME inputs, and
indicator LEDs
that is not attached to any single machine. Combining these parts into a simple separate unit simplifies playing with random scrappy machine parts like scrap CD/DVD drive sleds. The major parts cost less than $10, if you don’t already have them lying around waiting for a project, and the rest can be whatever works from found scraps.
…emphasizing “scrap” for the 2020 Scraps Speed Challenge…
The Scraps Challenge description says there’s a difference between trash and scrap - without saying much about the difference. …?… So let’s say: stuff intercepted on the way to landfill and directly restored or repurposed from its discarded form was trash; and retained leftovers or bits harvested out of forgotten trash of the past because it could be raw material for anything is now scrap.
Everybody has access to different scraps of different kinds, so this is more of an inspirational example than a repeatable how-to. You can get to the same end by the road that starts where you are.
Supplies:
Some amazing projects by other people provide the important parts that make this work.
Software
Grbl - “no-compromise, high performance, low cost” motion control software “utilizing every clever feature of the AVR chips” to extract high performance from low-cost Arduino boards like UNO
Hardware
Stepper motor driver modules - in a format pioneered by Pololu Robitics & Electronics. Driving stepper motors to their best performance is tricky business. There are several sophisticated ICs to help with the job and Pololu developed a tidy package that has become a common modular interface for many different stepper driver ICs.
Protoneer CNC shield - all the power and interface details to go between (up to) four stepper drivers and an Arduino board in a tidy “shield” format
Arduino UNO R3 - a microcontroller board that runs Grbl and fits the CNC shield
All of the above in a single kit, for less than $10 (USD, at time of writing)
~7 Volt DC regulator - to reduce the higher voltage motor supply for input to the Arduino’s on-board regulator. LM317 adjustable regulators — a common part for nearly half a century — are available in simple adjustable modules so inexpensive that it’s hard to justify any greater effort on that front.
“Dupont” connector parts
Scrapware, Electrical
laptop power brick - typically 16-20 Volts and more current than a few Pololu-style stepper drivers can handle. Protoneer CNC shield silkscreen indicates 12V-36V. A4988 stepper drivers, as in the all-up kits linked above, call for 8V < supply < 35V.
Power input connector(s) - I like “5-way” binding posts for flexibility
Hookup wire - heavy enough to carry more total current than your motor drivers can handle
Switch - rated for more total current than your motor drivers can handle
Fuse - rated for less total current than your motor drivers can handle
Fuse holder
Conveniently suitable scrap PCB with
Momentary switches (3) - for ABORT, HOLD & RESUME inputs
LEDs (3) - for controller power, motor power & motor ENABLE indicators
room for motor power switch
connector and signal wires
Discrete SMT
330 Ohm resistors (3) - current limiting for LEDs
NPN transistor - to switch the high-voltage indicator LED
47 kOhm resistor - limit transistor base current
What‽ Collecting scrap chip resistors & SOTs? Seriously? Yup. I grew up in ye olde through-hole age and started learning these newfangled surface mount things by harvesting, identifying, collecting and re-using the easy parts
Scrapware, Mechanical
wood scrap - approx 6in x 3in / 15cm x 8cm / hand x finger
or other soft-ish insulating material
or hard and/or conductive material plus PCB standoffs
boxy thing to mount switches & indicators and cover fuse/switch wiring
various screws”