# Do I need power supply totalling my current needs to maximum of my current needs?

My prototype project has these 3 components currently:

• US-17HS4401 stepper motor, rated at 12V / 1.7A
• MIG-400 6V DC motor, 6V / 10A max (although it was spinning fast enough at 3.75A)
• Particle Photon, 5V / 0.5 A
• 2x L298N driver controller (reduces voltage to motors by 2V)
• 1x DC-DC LM voltage regulator.

I'm looking to buy a power supply for my project. Looking at this the total current draw is: 5.95A, the maximum draw is: 3.75A

1. My question is does the power supply need to add up the current required or just provide the maximum required?
2. Since each device has different current requirement do I need to add a step down module for amps before each device?

What will happen if my device is given more amps than provided? Do I need to place before it any safeguards?

Rough schematic of my setup:

• No, it needs to add up to the power required. For example if you choose a 12V supply for a 1.7A and a 6V 10A motor, ( 60W = 12V 5A. You'll lose power converting 12V to 6V so call it 12V 6A) you need a minimum of 7.7A not 11.7A. If you restrict the motor's budget to 3.75A you'd better make sure it never needs to generate more torque than you are testing it with now; torque (NOT speed) controls current.
– user16324
Commented Mar 16, 2020 at 14:41

You need to provide current to the sum of the maximum of all components.

Your powersupply must be able to handle it if all of your components try to pull their maximum current at the same time. The only way to guarantee that is to have a powersupply that can deliver the full total of the maximum of all components.

You don't need to regulate the current to each component. All of your stuff is designed for a regulated voltage - current will take care of itself.

Where you will have a problem is with the LM2596.

Typical LM2596 modules are designed for 3A. Your MIG-400 motor can draw up to 10A. The LM2596 will probably fail to deliver the required current, and the voltage will drop.

A drop in voltage will cause the Particle Photon to mis-behave - potentially making it send incorrect signals to your motors and there by causing your device to run amok.

You need a separate regulator for the motors and the Particle Photon.

Alternatively, you might either provide a second powersupply of 6V for the MIG-400 motor or switch to a 12V motor instead of the 6V MIG-400.

• Thank you for the explanation. I have few extra voltage regulator modules so it should not be a problem. I'll look for a voltage regulator that can possibly handle more. Tho powering the motor at 3.75A looked to be more than enough top speed for what I was doing. Commented Mar 16, 2020 at 12:13
• Think now I'm more concerned if 10V 1.7A will be enough for the stepper motor. Since the L298N reduces voltage by some ~2V Commented Mar 16, 2020 at 12:15
• Do you know of a module similar to LM2596 that can work with more current ? Commented Mar 16, 2020 at 12:19
• The L298 is a separate problem. It uses bipolar junction transistors to drive the motor. It will always drop a couple of volts.
– JRE
Commented Mar 16, 2020 at 12:22
• I don't know of a standard replacement for the L298. I haven't built anything that would require it. Try searching for "L298 mosfet replacement" on google. That turns up a lot of projects that use mosfet based chips. Check them out, see if there's anything that will fit your needs.
– JRE
Commented Mar 16, 2020 at 12:24

when designing my led walls (60 amps 5v per section/panel) I always make sure to not go over 80% constant draw. I like my power supplies cool. but it depends on your duty cycle and how much its on though, finding out a cheap power supply that has a peak efficiency rating at 50% load is bad.