Here is a gas leak detector circuit that detects the leakage of LPG gas and alerts the user through audio-visual indications. The circuit operates off a 9V PP3 battery. Zener diode ZD1 is used to ...

The 16-V zener diode protects Q1’s base from excessive voltage. Designers can use a 12-V zener to match the operating voltages exactly, but the 16-V diode adds a 4-V margin of flexibility in the ...

By making diodes, it is possible to produce all three basic optoelectronic devices -- photodetectors, photovoltaic cells, and LEDs; the MIT team has demonstrated all three, Jarillo-Herrero says.