Intro
My friend Jeff had a fridge. It broke. Now I have a broken fridge.
Peltiers
This is a peltier fridge. Meaning it uses
the thermoelectric effect to
to cool. We will get into driving Peltier junctions later.
Fridge Design Overview
The basic design is an insulated box, with one or more cooling units
(this one has two), driven by a control board. The cooling units
consist of a small heatsink and fan on the inside of the box,
a large heatsink and fan on the outside of the box, and a
Peltier junction between them. The control board converts
utility power, commonly at 100 to 240 volts AC, to DC voltage
to drive the Peltiers.
Brokenness
Peltier fridges can fail in a few different ways.
- Fans can jam with dust - this prevents removing heat from the Peltier junctions
- Peltier junctions can fail, commonly from
thermal stress
- Control board can wear out
In this case, the control board produces 12V for the fans, but
no longer converts the 12V down to drive the Peltiers, so the control board
is bad.
Fixing
A new control board is required. I'll likely be moving to a simple
Bang-Bang controller, although more advanced and efficient designs
are available.