On my first semester I was tasked to build a simple electronic circuit with diodes and a transistor where depending on 2 certain voltage levels applied on the circuit two possible effects would occur.
The circuit consists of:
2 LEDs( Light Emitting Diode)
3 resistors ( Two 1000Omhs and one 2200 ohms resistor)
1 NPN transistor
1 Zener Diode (1N5349BG)
The circuit works with 2 voltages: 12 and 24 volts. If 12 volts is applied, the current will only flow to the red diode, because the Zener diode will not transfer any voltage as its limit its 12 volts and the green led will stay off. Now, if the voltage is increased to 24 volts the Zener diode will allow the flow of the current, also the Zener diode regulates itself at his Zener breakdown voltage, it will send the remaining voltage to the 2200-ohm resistor, because of the resistor, a small voltage reaches the base of transistor activating it, allowing the remaining current to flow from the collector to the emitter. Keeping the green LED on and the red one off.
Circuit Diagram
Circuit Model
12V Running
24V Running