Latest Electronic Circuits
Human generations are able to hear frequency which has a range from 20Hz to 20 KHz. All the rest frequency above this is considered as a ultrasonic frequency. Many animals and insects are able to hear this range of frequency. Usually in mosquitoes ultra sound is generated by the male ones and female one receives that one. While after breeding female mosquito mainly used to avoid this frequency. And this circuit produces the same frequency as the male one generates, and these creates a stress on the antennae of the mosquito and these keep them away.
The lifts remain idle for most of the time and it is used during peak hours only like in morning from 6 am to 10 am and in evening from 5 pm to 9 pm. So out of 24 hours a lift is used mostly for 8 – 10 hours. Now the problem is, in a lift there is always a fan and a light that stays on continuously. Even if lift is not in used for longer period of time. Although the ON/OFF switches for fan and light are already given, no body turns it OFF. So the fan and light inside the lift stays ON continuously and makes complete waste of electrical energy. Such a waste of valuable electrical energy in this era is not at all desirable.
Presenting a simple circuit called smart DC fan that senses any person near by and turns on. when there is no any person it turns off automatically. Later on I have given one more circuit that is with a small change in the same circuit so that it can switch on and off 230 V AC light and fan at a time inside lift.
In most of the homes the door bells are conventional ding-dong type. Most of us don’t like its sound. Due to mechanical moving parts with spring mechanism its long term durability is questionable. I had also one such door bell in my home. After a period of time its performance deteriorates and one time it becomes completely intolerable because of its noisy irritating sound.
The new types of door bells available in market are bird sound door bell. They are costly and even I didn’t like it because of its high frequency and high volume sound output.