# Multiple 12V devices with one power supply

On my workbench, I have many 12V devices, each with a small wall wart power supply. I'd like to buy a single, larger, power supply, and build a simple parallel circuit to power them all. I don't want to damage anything. Is there any circuitry necessary, besides wiring? I'm wondering if I would need any type of isolation or noise reduction, and would the voltage fluctuate as I plug and unplug devices?

The devices here are: 4x RAID hard drive, wifi router, 2x fans, LED strip, 7" OLED monitor. It's about 150W total.

I'm thinking of a power supply like a Meanwell GS-220A12.

• You have to calculate the overall current consumption of the devices and make sure that the power supply can handle the amount of current. – Bence Kaulics Jul 12 '16 at 17:04

I'm wondering if I would need any type of isolation ...

That would be an isolating DC-DC converter and would be at least as big as the wall-wart which, presumably, has been sized for the load so you would lose the benefit.

... or noise reduction, ...

Some local capacitance might be a good idea but, in theory, shouldn't be required.

... and would the voltage fluctuate as I plug and unplug devices?

This depends on the transient response of the power supply and should be specified on the power supply datasheet.

One thing that you are assuming is that they all share a common ground connected to the 12 V common. This may not be the case.

simulate this circuit – Schematic created using CircuitLab

Figure 1. Any device with full-wave rectifier reverse polarity correction will have its internal ground raised by 0.7 V.

Introducing a device with input protection as shown in Figure 1 could result in problems. The internal ground will be 0.7 V above your common 0 V line. Connecting, for example, a USB lead to another device may correct the problem but now all the power return will be through the USB lead. If this isn't rated for the current the voltage may rise on that line. You could spend a lot of time debugging this and potentially causing some damage.

Proceed with wisdom and caution.

12V supplying 150W makes an output current of ~13A. You will definitely need to watch out for surges when the bigger loads are switched off, or dips when they are turned on. The effort needed to to neutralize these will leave you with nearly the same amount of circuitry as the individual adapters. My advice, split them up. The heavy loads like fans and non-sensitives like LED strips go on one circuit. The sensitive loads like the hard disks go on another