ELECTRONIC HAND DRYER

Here is an interesting project. One can dry damp hands without using a towel by using this project. The moment we put our hands in front of the glowing bulb, we start felling hot air coming from a fan and a heater. The hands are dried. When we remove our hands then the heater and the fan stop working automatically. This circuit is senses the presences of hands through an LDR on which the light beam falls from the bulb. During the time when the bulb is lighted , the main circuits remains off because there is low resistance in the LDR but when the light from the bulb is cut-off our hands then circuit is activated. The main circuit contains IC 555 and a relay.

HUMIDITY CONTROLLER

This circuit is used to automatically switch ON/OFF machines like motor pump of room cooler. The circuit works on 6V DC supply. In this circuit a timer IC(NE 555) is used. Its pin no.4 and 8 are given the positive supply and pin no.1 is given the negative supply. Resistance R1(1k) and capacitor C1 (470 MF/16V) from the charging/discharging process. On/Off time depends on the Value of R1. Base of transistor T1(AC 187) is connected with IC pin no.3 through a resistances R3(8.2K). Its Output is given the relay. The moment Relay switches ON, the motor starts and in the same when the relay switches OFF the pump also switches OFF.

SELF RESETING INTRUDER ALARM

This project has unique facility by which it automatically shuts OFF after sounding an alarm for about 10 seconds. IC 555 has been used with in stable mode. As long as light continues to fall on the LDR IC pin no.2 continues receiving positive volts and the output remains  zero. As soon as the light falling on the LDR is interrupted then the pin no.2 gets negative pulses and the IC works for 10 seconds. After this the circuit is automatically reset.

MUSIC BY LIGHT

The circuit given here generates music in tune with the light. One IC 555 is used as an astable multivibrator although, we can also use two transistor in place of this IC as shown in figure. In both the circuits one LDR is used. As light falls on LDR of both circuits, current begins to flow. The of this current depends upon the intensity of light falling on the LDR. IC 555 produces audio frequency according to the flow of current and we can hear panoramic music.

IDENTIFY THE VALUE OF RESISTANCE BY SOUND

In the project given here, we can measure the value of resistance(0ohm to 10me) by hearing sharpness of the sound. Connected the probes at the two ends of a resistances and listen to the sound produced by the circuit. Particular values of resistances produce a particular sound by which we can identify the approximate value of the resistances.

PARTS LIST

IC:555

Heater Rod,small size Fan

Resistance: 100k,LDR,control 5m

Capacitor: 100MF,12V,0.001

Diodes: IN4001

MOSQUITO REPELLING CIRCUIT

This mosquito repelling circuit is made around the IC 555. Here, the IC 555 is used an oscillator which generates frequency in the range of 200Hz to 62KHz. This frequency can be adjusted by using the preset R2 connected in the circuit.

PARTS LIST

IC:555

Loudspeaker or Earphone: 8E

Resistance: 220E,controls 1M and 5r

Capacitor: 0.1, 100MF,10V,0.005