Capacitor fopr Stepper Driver

Hi All.
Following a few articles to use an Uno to control 2 stepper motors, for a small hobby device I am wanting to construct.

I have :
12V DC PSU
Uno
Nema 17 stepper with A4988 driver
Nema 23 stepper with DRV8825 driver

The recommendation I have seen, is to have a capacitor, across the Positive & Ground lines, between the PSU and the Stepper.
A few different Capacitor Values have been mentioned ( 47uF to 100uF )

I have ( on hand ) 10uF 25V and also 470uF 16V.

Would either of these capacitors ( or a combination ) be sufficient ?

Do I need a separate capacitor for each stepper, or only 1 capacitor on the line that goes to both drivers ?

If I want to power the UNO from the same 12V supply, is it better to branch off from the PSU directly ( before the capacitor/s ) to the UNO, or branch off to the UNO after the capacitor ( on the stepper side of the capacitor ) ?

You need one capacitor per driver, mounted close the driver itself. The problem solved by the capacitor is at least partly due to the inductance of the power leads between the driver and the motor power supply.

It is usually OK to use larger values than recommended, but not smaller.

OK. so use the 470uF 16V capacitors.

And 3 branches from the PSU ?

Branch 1 to the Uno

Branch 2 to Capacitor # 1 to Driver # 1

Branch 3 to Capacitor # 2 to Driver # 2

Sound correct ?

jremington:
It is usually OK to use larger values than recommended, but not smaller.

As long as they aren't too much larger. 5x more than recommended (470 instead of 100) is usually fine. Don't go crazy and use supercaps though.

DaveO:
OK. so use the 470uF 16V capacitors.

And 3 branches from the PSU ?

Branch 1 to the Uno

Branch 2 to Capacitor # 1 to Driver # 1

Branch 3 to Capacitor # 2 to Driver # 2

Sound correct ?

Correct. This is called a “star” configuration, since everything is tied directly to the source.

Thank You both for the advice

Jiggy-Ninja:
As long as they aren't too much larger. 5x more than recommended (470 instead of 100) is usually fine. Don't go crazy and use supercaps though.

Agreed. And that's not as much for the capacity, but for supercaps being very different animals than regular electrolytic capacitors. For starters it'll be hard to find one in high enough voltage rating to work with a typical 12-24V stepper power supply...
Many stepper driver boards have decoupling capacitors on board already - often a tantalum one, those little beige blocks. Remarkably small for their capacitance. If so, no need to add an extra cap.

wvmarle:
If so, no need to add an extra cap.

I assume that there is no harm in adding a capacitor anyway, considering the stepper drivers are replaceable - maybe the next replacement does not have the on board capacitor

One would hope every pre-built module has at least minimum decoupling - but at the high currents
used by motors some more is useful to help tame noise on the power supply wiring.