Network Lead Tester Project

Thu, 02 Feb 2012 15:55:13 +0100

This project was designed for confirming the continuity and correct wiring of computer network leads which have 8 wires, but it can be used to check any lead with up to 8 wires by using appropriate connectors. For example stereo audio leads with 5-pin DIN plugs can be checked by just using the first 5 LEDs. The tester is simple but it can save a great deal of time when making up leads and it is much cheaper than the more sophisticated alternatives!

The tester works by connecting each wire to an output at one end and an LED at the other end. The outputs are switched on one at a time in sequence so that a correctly wired lead will make each LED light in turn. The 4017 IC counts up to 10 so there is a pause (for the 9th and 10th counts) before the LED sequence repeats. If the LEDs light up in the wrong sequence one (or both) of the connectors is wired wrongly. If an LED fails to light it indicates a broken connection. Please note that the RJ45 computer network plugs cannot normally be re-wired, instead they must be cut off and replaced.

This project uses a 555 astable circuit to provide the clock pulses for the 4017 counter.

TV Remote controlled home appliance circuit

Wed, 01 Feb 2012 19:54:25 +0100

This is one of the popular EFY circuit. i build this one very easily. The circuit consists of very less components and simple in design.

Connect this circuit to any of your home appliances (lamp, fan, radio, etc) to make the appliance turn on/off from a TV, VCD or DVD remote control. The circuit cane activated from up to 10 metres. The 38kHz infrared (IR) rays generated by the remote control are received by IR receiver module TSOP1738 of the circuit. Pin 1 of TSOP1738 is connected to ground, pin 2 is connected to the power supply through resistor R5 and the output is taken from pin 3. The output signal is amplified by transistor T1 (BC558).

The amplified signal is fed to clock pin 14 of decade counter IC CD4017 (IC1). Pin 8 of IC1 is grounded, pin 16 is connected to Vcc and pin 3 is connected to LED1 (red), which glows to indicate that the appliance is ‘off.’ The output of IC1 is taken from its pin 2. LED2 (green) connected to pin 2 is used to indicate the ‘on’ state of the appliance. Transistor T2 (BC548) connected to pin 2 of IC1 drives relay RL1. Diode 1N4007 (D1) acts as a freewheeling diode. The appliance to be controlled is connected between the pole of the relay and neutral terminal of mains. It gets connected to live terminal of AC mains via normally opened (N/O) contact when the relay energises. you can use any NPN transistor inplace of BC548. You can also use SL100 or any NPN transistor lying around you.

The delay depends on the C1 capacitor. Using higher value capacitor will create more delay and using less value capacitor will switch the circuit more than 2 times when you press a remote. Analyse the circuit by placing the 10uf capacitor in place of C1 (100uf).