Delayed Turn-on Relay Switch

Here the circuit schematic of a delayed turn-on relay driver. It has capability to produce adjustable time delays for up to several minutes with reasonable accuracy.

Proximity Infrared Detector

This is the simple circuit of proximity infrared detector, proximity sensor based? infrared. The applications of this circuit are the most varied. From placing it in the front door to prevent people stop in front of this circuit, or even placing it in the back and front of the car to warn other drivers when… Read More »

Light Alarm with Timer 555

Here is the simple and low cost light alarm circuit built using timer IC 555 as the sound generator and a LDR to sense the environment light. This alarm is activated when the light beam on the LDR photocell is interrupted (You can use the light of a flashlight bulb which will make you a… Read More »

Scoring Display with 7 Segment LED

This is the circuit diagram of game scoring display using 7 segment LED. This circuit consist of a timer IC, two decade counters and a display driver along with a 7-segment LED display to show the score. The game is simple. As stated above, it is a scoring game and the competitor who scores 100… Read More »

Aquarium Temperature Probe

This is the electronic circuit diagram of aquarium temperature probe capable to monitor the temperature of water and indicate the rise in temperature through audio-visual indicators. This circuit uses diode 1N34 as the temperature sensing probe. The resistance of the diode will be vary depends on the temperature in its vicinity.

Laptop / Notebook Protector

This is laptop / notebook protector circuit to protect your laptop or notebook or netbook from being stolen. Fixed in-side the laptop case, it will sound a loud alarm when someone tries to take the laptop. This highly sensitive circuit uses a homemade tilt switch to activate the alarm through tilting of the laptop case.… Read More »

Adjustable Symmetric 1 to 24VDC, 1A Power Supply

This is the circuit diagram of adjustable symmetric 1 to 24VDC, 1A Power Supply. This power supply give dual output positive and negatif output, you can adjust both positif and negative output (+1 to +24VDC and -1 to -24VDC). This kind of power supply also known as dual polarity power supply or splitted power supply… Read More »

4 Stage FM Transmitter

This is the FM transmitter circuit which apply 4 radio frequency stages, that are a VHF oscillator designed around transistor BF494 (T1), a preamplifier designed around transistor BF200 (T2), a driver designed around transistor 2N2219 (T3) and also a power amplifier designed around transistor 2N3866 (T4). A condenser microphone is wired at the input of… Read More »