Voltage Level Detector
Sometimes we might need to know when a voltage exceeds a certain level We could use a voltmeter, but we might not want to look at the Meter all the time. The solution would be a circuit that would alert us by a LED or the Lamp, when voltages exceed certain levels.
Here's a circuit that does just that. You can figure out how this Project works by looking at the schematic. "When the two long wires are connected to a voltage less than 2 volts, nothing will happen. But when a voltage of overt 2 volts is applied, LED 1 will light up.
This is because the voltage is high enough to overcome the resistance of the 1K resistor connected in series with LED 1. When the voltage rises to from anywhere 5 to 7 volts, the Relay will operate and the Lamp will come on.
You can use this Project to make sure battery voltages are above certain levels. It can also be used to warn when voltages in a circuit are getting too high. Don't use this circuit to measure voltages above 3 0 volts higher voltages might cause damage to the parts used in the Project, Can you think of some situations where a circuit like this might be used? (An electric power generating facility is one example ...)