Sounds like an oversimplified school problem, eg. you are equipped with 10%
of the issues that need attention. So start by not complicating it. Example if
you are given no tolerance of switch point, assume no consideration here. Or
is there any minimum time a load, once switched on, has to stay on... Any safety
concerns ? But in closing of your design make a list of design considerations you have
thought of but not asked for in problem, that way prof (hopefully) will give you
more credits.
Basic decisions you have to make :
1) Power switched on low side or high side of load ?
2) Develop a Vref for the trip point, eg. the 0.5V trip point.
3) Power for the solution circuit, where does it come from.
4) As Klaus mentions, hysteresis, you will need to choose a width. And then
calculate the R's needed to implement.
5) Choose a comparator. You can get comparators as duals, some with Vref in them,
some a combination of a comparator and an opamp, many low power (if TEG is only
power in system every mW wasted on peripheral circuits a concern). To select a
comparator go to Digikey website and use filter tools to find what you want. or
just stipulate in solution comparator should have the following features......
Do you have to build a prototype solution ?
Lastly you can always consider a low end processor to do this, using A/D and its
internal Vref and code to implement the detection and hysteresis (in code). Like
an ATTINY85 Atmel type of chip.
Regards, Dana.