Circuit 02: Voltmeter from 0 V to 12 V

The voltmeter circuit functions basically the same way as circuit_01:

• When the voltage at SIG is 0 V, then all LED's are off.
• When the voltage at SIG is 1.25 V, then all LED's are on.

We have to make sure that when the voltage at the top of the voltage divider is 12 V,
the voltage at the point between R1 and R2 is 1.25 V.

When we choose R2 to be 1K Ω The resulting voltage at the point between R1 and R2 is

and we want U to be This leads to a value for R2 of We can choose a more readily available value that is larger, for example 10K Ω,
but not smaller.