Single wall power input for Wemos D1, peltier, screen and air pump.

Hi all, Fairly new to electronics, been gradually teaching myself. I'm working on a project that I want to power from one power source.

The Peltier says it needs a 12v 6A power supply and I'll be needing this as I'll be adding a large heatsink. The air pump needs 6v with a current of 0.45A The screen needs 5v with a current of 0.45A.

So, my thinking was that I could get a 12v 8A power supply and split it using a barrel jack squid so that the peltier is powered and constantly on and the Wemos D1 will also have power. I can then use the 5v rail with a transistor and diode to power the air pump and connect the screen to the 5v rail also. When the pump and the screen is on that will be close to 1A which the max rated for the Wemos.

I'm worried that the voltage will be too high for the Wemos regulator, especially at 1A. Does anyone know if this will work or have any suggestions on how to power the project from 1 power supply?

Cheers, Matty

I'm worried that the voltage will be too high for the Wemos regulator, especially at 1A.

You are right. You don't get the 1A output when you give it 12V input. That's why the specifications usually show odd voltages like 7V.

Get a large enough 12V supply and then some switchmode converters to provide the 6V and 5V power. Pololu sells some great ones. I would probably run the Arduino-Wemos from the 12V or 6V rail (check specifications for minimum voltage) as the onboard regulator will be able to filter out fluctuations.

Thanks for the reply! So ideally I'd run everything separately from the power source, none from the arduino Wemos itself. That makes sense.

I'm totally new to this, what is a switchmode converter? I've googled it but not sure if I'm looking at the right thing.

what is a switchmode converter?

There are basically two types of voltage regulators: linear and switching.

Linear regulators waste all unused power as heat and usually come in single IC packages. External capacitors may be required for stability and smoothing.

Switching regulators generally require external coils and/or capacitors and switch the [u]input[/u] current on and off to produce a relatively smooth output at different voltage. With a few exceptions they are more efficient than linear regulators.

Thanks for the reply. Just to make sure I understand.

Say I get 2 switching regulators. One 5V and one 6V max output 1A each. Do I get a 12v 8A power supply? 6A for the peltier, which I'll connect directly to the power supply. 2A for the switching regulators? Both regulators will never have anything connected that will draw more than 0.5A.

Do I understand that correctly? Sorry for all the questions - this is the first time I've tried to power a few things from one supply, want to make sure I'm safe.

Switchmode power supplies are very efficient. 95% of the power input comes out the output. A 5V 1A output is 5W. So you need 110% of this or 5.5W input. At 12V, that's 0.45A, or maybe 0.5A to give yourself some margin.

So a 6.5A power supply would meet your specification. That's a very specific number so you have to round it up to whatever power supply you can afford. 7A or 8A would work.

12V and 5V dual rail power supplies are available. An old PC power supply would probably do it if you don't mind the size.