Recommendations for Shared Power Supply Circuit

I have a project involving step motors, a solenoid, and a relay module. These components will be controlled by an Arduino.

Motor 1: 6.8V 1.7A
Motor 2: 2.0V 1.2A
Solenoid: 5.0V ???A
Relay Module: 5.0V 0.16A

As you can see, it’s a mishmash of voltage and amp requirements. I was planning on using separate transformers to power these components, but I am hoping it may be possible to use a single transformer and reduce the voltage with voltage regulators.

Note: The Arduino itself will be powered via USB.

Note: The drivers for the stepper motors will always be powered. The solenoid and relay module will require power intermittently. To be safe, it seems that a minimum of 4A must be provided by the power supply.

If one used a single DC power supply with 4A output current, how simple would it be to create a circuit to deliver 6.8V, 2.0V, and 5.0V? I have drawn the attached (overly simplified) schematic as a starting point.

Specifically what capacitors would be recommended?

Are any other components necessary?

Using this set-up, how stable would the Vout current be?

What level of efficiency could I expect from this set-up?

I found some highly efficient voltage regulators from the V78 Series. Would using these regulators provide any further benefits beyond energy efficiency?

Can you explain more about those stepper motors - one of them looks suspiciously like a low-impedance bipolar motor that would normally be driven via a chopper driver from 12V or 24V or more... The other looks quite chunky (NEMA23?) and needs 1.7A driver which limits the possibilities for a driver.

You need to figure out what drivers before choosing supplys.

Motor 1 is a high resolution step motor (datasheet), which will be driven by the DRV8825 driver from Pololu.

Motor 2 is a Nema 17 (see datasheet attached), which will be driven by the Schmalzhaus BigEasyDriver.

Nema 17 Datasheet.pdf (1.39 MB)

Does anyone have any suggestions/recommendations/insights on this?

In general the voltage for supply of steppers is much higher than the motor voltage rating.

For example the ultimachine/rambo can use 12v or 24v, but the logic is all 5v. It works well with nema 17. The controller will current limit as set to drive the stepper, which also limits the motor voltage. So if you have a controller already, see what voltage the controller needs, and it will deliver the required voltage to the stepper. Many controllers are controlled by 3.3 to 5v, but have a different voltage source for the motor, 12v to 24v. See a4982 controller, google will list several data sheets for it.

(I am by no means an expert...)