Beer Tap Project (involving Peltier / Compressor)

Hi there,

I'm working on a DIY beer tap project for which I need to cool down a Keg using a Peltier device (TEC1), cool down a water circuit using a second Peltier device (TEC2), use an air compressor and a bunch of sensors. Everything is controlled via an arduino (NodeMCU in the diagram).

Im planning on using an old laptop power supply (19.5V-10.3A).
So far to get suitable voltage for all devices, I'm using voltage divider circuits.. I am not an electronic specialist and was wondering whether my approach was correct or if I should use a different one.

Hope I gave enough details.

Any input would be greatly appreciated.

You may have drawn what look like the mosfet gate pull down resistors incorrectly.
Can you post a link to the Peltier element you are using. I'm curious about the cooling effect for this application.

You are right, I amended the diagram with the correct pull down resistor wiring.
As for the Peltier device, here is a link to the datasheet

Any feedback on the voltage divider approach ?

novaecaine:
Any feedback on the voltage divider approach ?

The voltage divider approach is wrong.

You have calculated resistor values to give you the required voltage when no load is connected, but as soon as you connect a load (which is effectively in parallel with the lower resistor in the divider) then the voltage will drop drastically.
Also the voltage will vary according to how much current the load takes.

Voltage dividers are alright for reducing signal levels, but useless for power control.

You need to use a voltage regulator, that will give out a constant voltage.

Thx John,

That's a straight and helpful answer.
I'll dig out some info on voltage regulator and update the circuit.

Are you sure a Peltier can cool a keg? Have you done any experiments or have you seen it done?

I've seen a can cooler (for one can) and I've seen a tiny refrigerator that can hold a 6-pack.

Small Kegs yes (6L). Devices like PerfectDraft from Philips or BeerTender use peltier.

Btw is it relevant to keep the voltage divider to power the Arduino's 3v3 ?

ok here is an updated circuit with voltage regulators instead of voltage dividers.
I skipped the sensors and the fans to focus on the compressor (blue) and the 2 Peltiers (red).

Does this make more sense?

Thx a lot

LM338 datasheet
TEC 12706 datasheet