Sorry, yes, I was going to use a 19V power supply until I decided that using a shield and following other people's examples is a better match to my (in)experience!
The 19V supply is entirely fine if the CNC shield, the motor drivers on it and the steppers will handle that voltage.
The shield I'm planning on using is this.
This certainly has no electronics. You would want to check the capacitor voltage ratings. I haven't checked to make sure that it does not connect "Vin" to the UNO.
People seem to connect a 12V power supply to it and use that to drive both the Arduino and a servo.
I'm not sure how they get away with using the 5V pin to drive the servo. As far as I can tell (and I don't have one in my hands yet) the 5V pin on the shield is just an extension of the one on the Uno.
Well, they would need to provide a 5 V supply with sufficient current capacity to drive the servos. The on-board regulator on the UNO does not even count for such a consideration.
I'll give it a try and see what I get. (my project uses 2 servos but I'll try powering one to start)
Give what a try?
I've also ordered a step down module which should give me 5V 3A from a 19V power supply. I'll try using this to power both the servos and the Arduino and drive the steppers at 19V (which I read is better in some way).
The switchmode regulator is slightly more efficient at the higher voltage, and requires less current. That one should be OK.
In terms of physically connecting the output of the step down module to the servos and the Arduino, how should I do it?
Do I solder multiple wires on the output?
Perfectly fine. Note that you need to connect both ground and supply from the same source, running as a pair to each device.
Use some kind of connector?
Fine, but not too easy to connect more than one wire to each terminal! Need to twist and tin the wires (if using multi-strand) before connecting. The better quality (than that pricey one) "chocolate block" strips have a metal tongue under the screw to protect the wires from crushing.
Use a power distribution board?
If it is convenient. Grossly over-priced at that site!
Splice the wires?
Interesting video. Didn't get to the end (yet - got to go to work now ) but need heatshrink over each splice.