Digital & Analog Based Mini electronics Projects Page_2

Digital & Analog Based Mini electronics Projects Page_2

11. Automatic School Bell:

Consider that a school has a total of eight periods with a lunch break after the fourth period. Each period is 45 minutes long, while the duration of the lunch break is 30 minutes. To ring this automatic school bell to start the first period, the peon needs to momentarily press switch S1. Thereafter, the bell sounds every 45 minutes to indicate the end of consecutive periods, except immediately after the fourth period, when it sounds after 30 minutes to indicate that the lunch break is over. When the last period is over, LED2 glows to indicate that the bell circuit should

12. Automatic Speed-Controller For Fans And Coolers:

During summer nights, the temperature is initially quite high. As time passes, the temperature starts dropping. Also, after a person falls asleep, the metabolic rate of one’s body decreases. Thus, initially the fan/cooler needs to be run at full speed. As time

Passes, one has to get up again and again to adjust the speed of the fan or the cooler.

The device presented here makes the fan run at full speed for a predetermined

Time. The speed is decreased to medium after some time, and to slow later on. After

a period of about eight hours, the fan/ cooler is switched off.

13. Automatic-Off Timer For CD Players:

Are you in the habit of falling asleep while listening to music? If yes, you’ll love this

Circuit. It will automatically start functioning when you switch off your bedroom

Light and shall turn your CD player ‘off’ after a predetermined time. In the presence of ambient light, or when you switch on light of the room in the morning, the CD player will Again start playing. Unlike the usual timers, you don’t have to set this timer before sleeping.

14. Battery-Level Indicator:

Normally, in mobile phones, the battery level is shown in dot or bar form. This lets you

Easily recognize the battery level. Here we present a circuit that lets you know the battery level of a device from the number of LEDs that are glowing. It uses ten LEDs in all. So if three LEDs glow, it indicates battery capacity of 30 per cent. Unlike in mobile phones where the battery-level indicator function is integrated with other functions, here only one comparator IC (LM3914) does it all.

15. Bicycle Indicator:

The electronic bicycle signaling unit described here uses low cost components and is a

Good Substitute too many commercially available versions. It works in an extremely different manner. and is convenient to operate.

16. Bicycle Lock:

The electronic bicycle lock described here is a worthwhile alternative for bicycle owners

Who want to make their bicycles ‘intelligent’ at reasonable cost. One of the benefits

of building it yourself is that the circuit can be used for virtually any make of bicycles.

17. Blown Fuse Indicator:

Generally, when equipment indicates no power, the cause may be just a blown fuse. Here is a circuit that shows the condition of fuse through LEDs. This compact circuit is

very useful and reliable. It uses very few components, which makes it inexpensive

too.

18. Call Bell With Welcome Indication:

Here is a simple call bell circuit that displays a welcome message when somebody presses the call bell switch momentarily. The alphanumeric display can be fitted near the call bell switch.

19. Car Anti-Theft Guard:

Here is a simple Anti theft car alarm device for your Car. It generates a loud alarm when there is an attempt of theft. When the intruder opens the door, the circuit senses the attempt of theft and after 2 minutes, the alarm will be activated. The time delay is provided to help the user to leave the car after arming with the device.

20. Cash Box Guard:

Most thefts happen after midnight when people enter the second phase of sleep called

‘Paradoxical sleep.’ Here is a smart security circuit for your cash box that thwarts the theft attempt by activating an emergency beeper. The circuit can also be used to trigger any external burglar alarm unit.