> The op wants a temperature control and doesn't care about efficiency, so
> just run the Peltier at 12V until you reach the temp, and then turn it
> on again every time the temp rises a bit.

While intuitively OKish, this is bad in practice.
It will produce the desired cooling result, but this thermally cycles
the Peltier device and leads to substantial lifetime reduction due to
thermal stresses .

PWM (also mentioned) is notionally less efficient, as also mentioned.
Add a series inductor and a catch diode and you have a buck regulator
(or an RL filter depending on where you are looking in from) with
goodish efficiency compared to optimum.

Even mild and/or partial insulation of cup from ambient will greatly
aid coolth availability.


     R
--=20
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