Turn on LED if certain voltage range is detected
While Reinderien's answer is technically correct, you might want to have more flexibility when defining your voltage window. You might find the following circuit more satisfying:



simulate this circuit &ndash; Schematic created using CircuitLab
This contains 2 essential building blocks: comparators, and AND gates. Vref (high) and Vref (low) are defined by potentiometers (R1 and R2). They're essentially knobs you can use to tune voltages.
OPA3 and OPA4 are voltage comparators; OPA3 is essentially a '&lt;' operator and OPA4 is essentially a '&gt;' operator. The component on the right is an AND gate. If both the input voltages coming in are high, the Vout is high. If one or neither is high, Vout is low. The result is the circuit implementation of the following pseudocode: Vout = (Vin &gt; Vref_low &amp;&amp; Vin &lt; Vref_high).