Using 48V 25A AC/DC power supply to power multiple components?

Question

I was basically wondering if I may be able to control a NEMA 34 stepper (6.2A rated), Arduino Mega, and a linear actuator with just this single power supply (48V, 25A)? The NEMA 34 stepper would max draw around 12.4A if both coils run so I was thinking that I could probably just run the rest of the components with the remaining V- and V+ pins on the power supply since there is probably 12A left to be used, which is more than enough since both the Arduino and linear actuator when being powered never went more than 1A.

Now I was thinking of using separate voltage divider configurations for both the Arduino and the linear actuator to be able to power them separately. I included a diagram below to better explain what I mean. Am I going about this the right way? I am thinking too that I would probably need to find resistors with a high power rating just because 48V is a lot and I read that the resistor could potentially burn if it is not specified to be able to handle that load.

NOTE: I'm basically just trying to make this more compact with what I have at hand. My dad has a ton of resistors (some really large and small in size) and I have some buck step down converters that can handle up to 30V. My initial idea was powering the linear actuator with a 9V battery and the Arduino Mega with another 9V battery but thats probably not the most efficient way although its an easy way.

Answer 1

Resistors aren't the way to do what you're trying to do. The output voltage of a voltage divider will vary with load, from the expected output voltage at no load and drooping severely with increased current draw from the output node.

In addition, resistive/linear methods of voltage control are highly inefficient (25% for 48 to 12V, ~10% for 48 to 5V), which makes linear regulators a bad choice. For example, your Arduino Mega will draw at least 50mA by itself, which translates to (48-5V) * 50mA = 2.15W of heat generation, which will heat up the junction of a linear regulator in an un-heatsinked TO-220 package by ~150C, so that's really a non-starter.

@greybeard has the right idea with a new switching converter. Given that motors have a starting surge that can be up to 3x the running current, I would look for at least a 25W 12V output switching converter and add as much bulk capacitance to the output as it will let you get away with. 50W would be even more comfortable.

With the output of the 12V converter, you could then use a linear regulator or another switching regulator to create your 5-7V rail for the Arduino since they're both cheap and easy at that power level.