Digital & Analog Based Mini electronics Projects Page_7

Digital & Analog Based Mini electronics Projects Page_7

61. Mobile Bug:

This handy, pocket-size mobile transmission detector can sense the presence of an activated mobile phone from a distance of one and- a-half meters. So it can be used to

prevent use of mobile phones in examination halls, confidential rooms, etc. It is also useful for detecting the use of mobile phone for spying and unauthorized video transmission. The circuit can detect both the incoming and outgoing calls, SMS and video transmission even if the mobile phone is kept in the silent mode. The moment the bug detects RF transmission signal from an activated mobile phone, it starts sounding a beep alarm and the LED blinks. The alarm continues until the signal transmission ceases.

62. Mobile Cell phone Charger:

Charging of the cell phone battery is a big problem while travelling as power supply source is not generally accessible. If you keep your cell phone switched on continuously, its battery will go flat within five to six hours, making the cell phone useless. A fully charged battery becomes necessary especially when your distance from the nearest relay station increases. Here’s a simple charger that replenishes the cell phone battery within two to three hours.

63. Motor Speed Controller:

A continuously working wiper in a car may prove to be a nuisance, especially when it is not raining heavily. By using the circuit described here one can vary sweeping rate of the wiper from once a second to once in ten seconds.

64. Non-Contact Power Monitor:

Here is a simple non-contact AC power monitor for home appliances and laboratory equipment that should remain continuously switched-on. A fuse failure or power breakdown in the equipment going unnoticed may cause irreparable loss. The monitor sounds an alarm on detecting power failure to the equipment.

65. Number Guessing Game:

This number guessing game is quite simple. In this game the player thinks of any number between 1 and 99. Then he scans the eight groups of numbers given in the eight boxes in the table. Each group corresponds to a specific switch (indicated on the top of each group) on an 8-way DIP switch. The person scans the numbers in each box and slides the switch corresponding to a box to ‘on’ position if he finds his number in that box. After having scanned all the eight boxes and switching on the relevant DIP switches, he is required to press switch S9 and the number thought of by the person is displayed on the 7-segment displays. After this, all switches on the 8-way DIP switch need to be turned off to try display of another number in a similar fashion.

66. Numeric Water-Level Indicator:

Most water-level indicators for water tanks are based upon the number of LEDs that glow to indicate the corresponding level of water in the container. Here we present a digital version of the water-level indicator. It uses a 7-segment display to show the water level in numeric form from ‘0’ to ‘9.’

67. Over-Under-Voltage Protection Of Electrical Appliances:

This circuit protects refrigerators as well as other appliances from over and under-voltage. Operational amplifier IC LM324 (IC2) is used here as a comparator. IC LM324 consists of four operational amplifiers, of which only two operational amplifiers (N1 and N2) are used in the circuit.

68. Parrot-Sounding Ac Doorbell:

Here is a mains-operated doorbell that produces parrot-like sweet voice without requiring any musical IC. The circuit is cheap and easy to construct. The AC mains is fed to the circuit without using any step-down transformer.

69. Pc Multimedia Speakers:

This circuit of multimedia speakers for PCs has single-chip based design, low-voltage power supply, and compatibility with USB power, easy heat-sinking, low cost, high flexibility and wide temperature tolerance.

70. Portable Lamp Flasher:

This circuit using a dual-timer NE556 can produce 1Hz pulses spaced 5 seconds apart, either manually or automatically. IC NE556 comprises two independent NE555 timers in a single package. It is used to produce two separate pulses of different pulse widths, where one pulse initiates the activation of the second pulse.