Programmable Current Source by LM317

Accurate and stable current supplies are generally needed in electronic labs especially for creating V-I curves, charging and discharging batteries, preloading power supplies and for many other purposes and applications.

Drive Multiple LEDs by Using Only One NiMH Cell

This simple circuit allows us to drive serially connected seven LEDs by using a single NiMH (Nickel Metal Hydride) AA cell. As you can see there are a few components, a CMOS 555 timer, an NPN transistor, an inductor, three resistors and two capacitors.

Switch Debouncer with Only One Inverter

This circuit acts as a debouncer that prevents multiple logic signal transmitting when a switch is pressed. It takes its logic power from only the remote pull-up resistor R2 and can be used in non-energized devices such as a device in a system that's just coming from the stand-by.

TTL Level - RS232 Level Converter by MAX232

This is a small portable RS232 - TTL converter circuit that is based on one of the most common ICs MAX232.

Simple Telephone Security Device

In the market, there are several types of telephone security devices which are generally simple but not cheap. On the other hand most of them do not guarantee protection against unauthorised operation

Series Protection Against High Voltage Transients

This circuit provides a series protection  that turns off the power switch using a serially connected high voltage MOSFET ( IXFH26N50l – Q1 ) power switch and a fast overvoltage detector IC, MAX1614.