[EugeneMDP (OP)]

I've always wondered how the toaster "knows" it's time to finish the job. How does this process work, especially in simple and cheap models?

[syhprum]

I have not dismantled my toaster but I believe when you adjust the control for the degree of toasting you vary  the heater current going to a thermally operated release switch that shuts down the toasting  operation.
My toaster has a button for frozen bread which apparently interpose a LED in the  heater current  circuit  delaying the cut off
These must be one of few domestic devices that do not include a computer of ENIAC complexity in their design !

[vhfpmr]

They don't, that's the problem with them.

I gave up using one because the required cooking time depends on how fresh and moist the bread is, so you either have to run several test slices first just to find the right setting, or stand over it popping the toast out every few seconds to check the progress. The 'timer' on mine was just a bimetallic strip that tripped when it was hot enough, so the required setting additionally depended on whether it was the first run from cold, or the toaster was already pre-heated by a previous run.

They're as much use as a chocolate teapot, so I use the grill on the rare occasions I eat toast. I eat exclusively brown bread these days anyway, which I don't think makes particularly good toast.

[Eternal Student]

Hi.

I just thought the timer control was a...  timer control... it just sets a time to stop the thing.

Best Wishes.

[evan_au]

These days it is probably done electronically and inscrutably, within a chip.

But you could get some clues by looking at what sensors feed into the chip.