Sajee tronics

T his circuit lets you locate wire breaks, so you can cut the wire  insulation at precise points and repair the breaks. The working of the circuit is based on capacitive effects developed in a tube detector. Before detecting breaks, it is essential to know which wire has a break. This can be easily detected using a continuity tester. Once the wire having a break is detected, signals from the col lectors of transistors T2 and T3 (points A and B) have to be applied to the two ends of that wire and a tube has to be run along the wire for detecting the break point. This tube actually forms a capacitor with the test wire. When the tube crosses the break point in the wire, there is a flip in the LED glow indicating wire break.                    The circuit is built around a 555 timer IC (IC1), CMOS NAND gate CD4011 (IC2), CMOS NOR gate CD4001 (IC3) and a few discrete components. IC 555 is wired as an astable multivibrator. Its output is fed to the detector circuit built around tra

This simple key-operated gate locking system allows only those persons who know the preset code to open the gate. The code is to be entered from the keypad within the preset time to operate the motor fitted in the gate. If anyone trying to open the gate presses a wrong key in the keypad, the system is disabled and, at the same time, sounds an alarm to alert you of an unauthorised entry. Figs 1 and 2 show the block and circuit diagrams of the key-operated code locking system, respectively. Connect points A, B, C, D, E, F and ground of the circuit to the respective points of the keypad. Keys S7, S16, S14 and S3 are used here for code entry, and the remaining keys are used for disabling the system. It is very important to press the keys in that order to form the code. To start the motor of the gate, press switches S7, S16, S14 and S3 sequentially. If the keys are pressed in a different order from the preset order, the system will lock automatically and the motor will not start. Fig. 1:

Normally, sound intensity up to 30 dB is pleasant. Above 80 dB, it becomes annoying. And if it goes beyond 100 dB, it may affect your psychomotor performance, detracting your attention and causing stress. Noise pollution may also affect your hearing ability.