Since the advent of electricity, people have used electricity more and more frequently, and electricity can be seen in streets and alleys. Of course, electricity should be controlled and overused, no matter how rich people are, it will cost a lot of money. Then, in order to prevent wasting electricity, people invented a switch that can delay time. This kind of work is usually seen in the garage or corridor. Do you know how it works?

About the selection of components:

The IC should adopt CMOS digital integrated circuit CD40 13, which is a double D flip-flop. This circuit is only half used, and the other D flip-flop is suspended. VS adopts small plastic sealed unidirectional thyristors such as 2N6565, MCR/KOOC-0/00-8, which can control any lighting circuit below/KOOC-0/00W ... VD/KOOC-0/~ VD4 is/KOOC-0/N4004 ~/KOOC-0/N4007 rectifier diode. The light-emitting diode can be a common red light-emitting diode, and the resistance is RTX type 1/8W carbon film resistance. C 1 and C2 are electrolytic capacitors of CD 1 1- 16V type, and C3 is a ceramic capacitor.

About the working principle of this switch:

There is a metal sensor outside the touch delay switch. When people touch it, it generates a signal to trigger the transistor to turn on, charging the capacitor, and the capacitor forms a voltage to maintain the FET to turn on the light bulb to emit light. After removing the handle, stop charging the capacitor. After a period of time, the capacitor discharges, the gate of the field effect tube becomes low potential, and the light bulb goes out.

The right side of the dotted line of the touch delay switch circuit is the general lighting circuit, and the left side is the electronic switch part. VD 1~VD4 and VS constitute the switch main circuit, and IC constitutes the switch control circuit. At ordinary times, VS is off and the light is off. VD 1~VD4 outputs 220V pulsating DC, which is limited by R5, stabilized by VD5, and filtered by C2 to output about 12V DC for IC use. At this time, the LED lights up to indicate the position of the switch, which is convenient for finding the switch at night.

There are many ways to make printed circuit boards. In my spare time, I can use painting, knife carving, self-adhesive sticking, thermal transfer and other methods to make plates. The following is an example of making a self-adhesive board.

1. Cut the copper clad laminate to the size required by the circuit diagram (47mm×32mm) and clean it.

2. Draw the printed board diagram of Figure 5- 1-2 on the adhesive tape (it can be copied or printed after scanning).

3. Stick the patterned adhesive onto the copper clad laminate and fully compact it.

4. Carve through the surface layer with a meat cutter to form the required circuit, remove the non-circuit part and clean up the residual glue.

5. When the circuit board is corroded by ferric chloride, the corrosion temperature can be about 60℃. The faster the corrosion rate, the lower the temperature and the longer the corrosion time.

6. Wash the corroded circuit board with clean water, punch holes according to the hole turning position on the pattern, and remove the glue on the circuit board.

7. Grind the circuit board with fine sandpaper and coat it with rosin alcohol solution for later use.

This kind of touch delay switch is generally used in corridors, garages, bathrooms, corridors and so on. In fact, it is very convenient for us to use this switch. When in use, it can be extended for a while by touching the metal object on the switch, which is more humanized. Because this switch is not often used, it has a long service life and does no harm to human body, so is it humanized and convenient to use this switch?