# How to correctly supply power to multiple 12 V devices wired in parallel?

I am an artist, building a functional miniature which contains multiple devices (3 12 V computer fans, 1 cooling pump, two LED strips totauling 14 segments of three or 42 individual lights, and 1 Peltier tile). They are currently wired in parallel. I have been using an adjustable power supply, and it works however it only works when I turn the supply up to 19 V, which I know is bad for all of the devices. This supply claims a max of 3.4 A output. I also have a power supply which provides 12 V and 6 A, which when plugged in is insufficient to power the device. I have tried calculating what the current draw of the device should be, however I am not sure what the current draw of the Peltier tile is or how to determine it, and my best estimate is the the device should use possibly 4-7 Aat 12 V. Why does it work when I give it additional voltage, and yet when using a higher amperage power supply (possibly sufficient) it doesn’t work? What would be a better hypothetical way to supply power to this device? How can I calculate the current the Peltier tile is drawing?

I am learning as much as I can about electrical engineering to safely build this object, and I know enough to hack together art objects, however I am not a professional, and I feel like I have come up against the limits of my ability to figure this out!

I do have a multimeter, which I’ve used to test the claimed voltage of my adjustable PSU, and it is accurate to what it is putting out.

• Use one PSU for the peltier, and a different PSU for everything else. Until you get yourself a multimeter, you're flying blind, so get one. It doesn't have to be the best one out there, any cheap multimeter is infinitely better than none. Feb 26 '20 at 7:56
• I should have mentioned that I have a multimeter, and when I measure the current the voltage is accurate to what the psu claims it is outputting. Feb 26 '20 at 14:35
• If you have the multimeter, I would suggest just connection the peltier tiler to the 12V 6A supply and measure the current with the multimeter as Amper-meter (nb : use the high current position if it has one (often 10A on cheap multimeters) Jan 12 at 18:46

The Peltier tiles consume a lot of power, and it sounds like you have no measuring equipment (multimeter) nor datasheets for the device.

It's safe to assume the tile alone consumes just about everything that your fixed power supply is rated for. I wonder how/if your adjustable power supply measures the voltage level when you set it or if it's just a knob with divisions and no indicator - in which case when you set the knob to 19V you are likely getting closer to the 12V you need to run everything.

• Should have mentioned I have a multimeter and the voltage is accurate from the adjustable psu- it has a multi-step switch with a claimed voltage at wash step. Interesting that the peltier consumes so much power, and I am already running another peltier in this device off a secondary psu, so that may be the solution. Thanks for you answer! Feb 26 '20 at 14:37

I suspect you might be having a large voltage drop between your power supply and all your devices. So even though your power supply says 19V maybe only 13 or 14V are arriving to you devices.

What is the cable section and distance between your power supply and your devices? Also check with your voltmeter what is the voltage arriving at your devices. If it is how I suspect then increase the diameter of your cables.