2N2222

Electronic Keys & Locks, Security & Saftey

One transistor code lock

Description. This is of course the simplest electronic code lock circuit one can make. The circuit uses one transistor, a relay and few passive components. The simplicity does not have any influence on the performance and this circuit works really fine. The circuit is nothing but a simple transistor switch with a relay at its […]

Audio Circuits

Low cost amplifer.

Description. No big deal here! You can make a decent power amplifier using just three transistors. All components used here can be obtained from your electronic junk box. Also you just need a 9V transistor radio battery to power this circuit. The circuit is ideal for a pocket radio or other hand held audio equipments.

Industrial Circuits, Test & Measurement Circuits

Humidity tester

Description. A variety of humidity tester circuits are available, but this  is a circuit which is as simple as possible. Using only a transistor, LED and few resistors, this circuit can be used to check the humidity level of materials like soil, paper etc. When the humidity in a substance increases the current conducted through 

Melody generator circuit
Tone generator circuits

Melody Generator using IC UM66

Melody Generator Circuit This is a simple project using the IC UM66. UM66 has an inbuilt beat and tone generator. This IC, with its three legs, looks like a transistor. This IC has many versions for playing different songs/beats. This project is suitable for beginners as its circuit is very simple. Description  The  UM66 series

water level indicator
Home Circuits, Test & Measurement Circuits

Simple Water Level Indicator

This is the circuit diagram of a simple corrosion free water level indicator for home and industries. In fact, the level of any conductive non-corrosive liquids can be measured using this circuit. The circuit is based on 5 transistor switches. Each transistor is switched on to drive the corresponding LED when its base is supplied

Electronic Keys & Locks

Electronic Combination Lock using IC LS 7220

A simple electronic combination lock is designed using IC LS 7220. This circuit can be used to activate a relay for controlling (ON & OFF) any device when a preset combination of 4 digits are pressed. The circuit can be operated from 5V to 12V. The LS7220 IC is a MOS digital lock IC that

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