Repair the bedroom lamp under the double control switch with electric pen
The light in the bedroom suddenly went out and decided to fix it. The light is controlled by a double control switch. The light originally has different brightness levels, three big lights are on, N smaller crystal lights are on, and all the lights are on. It is estimated that the electrical components inside the lamp are aging, and it is planned to change it to only the big light, and the flashing functions of the small lights are useless to us.
If a worker wants to be good at his work, he must first sharpen his tools. The following mainly talks about the electric pen. The electric pen includes the old-fashioned neon bulb electric pen (the test has electricity, the neon bulb lights up, and it looks red), and the digital electric pen I use (pictured below).
The multi-functional test pen (digital display type) has 12V, 36V, 55V, 110V, 220V files, can measure AC and DC (12-250V), and has the function of testing induction electricity (the hand contact is "Induction" in the above picture xxxx Test"), the highest voltage file displayed is the approximate voltage value measured at that time. The induction break test is used to test where the cable breaks. It is said that it cannot be immersed in water, and it will be reported as destroyed if it is immersed in water (expressing that it does not understand, who can test it).
Displayed as 12V36V55V110V220 means the voltage is 220 volts; displayed as 12V36V55V110 means the voltage is 110 volts; displayed as 12V36V55 means the voltage is 55 volts; displayed as 12V36 means the voltage is 36 volts; displayed as 12 means the voltage is 12 volts.
When measuring AC, press your finger on the direct detection contact ("Direct Test"); when measuring DC, press and hold "Direct Test", press the positive pole of the battery with the other hand, and the negative pole with the tip of the pen.
The working principle of both electric pens is the same: Ohm's law I=U/R and the total resistance relationship of the series circuit: R=R1 (person) + R2 (electric pen). The resistance of the human body is generally very small, usually only a few hundred to a few thousand ohms, while the internal resistance of the test pen is usually about several megohms, and the current through the test pen (that is, the current through the human body) is very small, usually less than 1 mA , when such a small current passes through the human body, there is no harm to people, but it can make the electric pen display (or the neon lamp is bright, or the digital display).
The voltage of the live wire should be 220V. When the switch is turned off, there should be no voltage on the neutral line; when the switch is closed, the neutral line may display a voltage of 55 volts or less (connected with an electrical appliance), or 110V (this is the electronics on the lamp in my home). Component failure shows 110V, it may also be that the live and neutral wires are reversed, in short, pay attention).
With the electric pen, first judge whether there is a problem with the dual-control switch, and finally check whether there is any problem in the light on the roof (the light in the middle of the roof is really difficult to operate). Soon, it was checked that there was no problem with the wiring of the double control switch, and there was no problem with the on-off. Dual control means that two sets of switches can control one light without affecting each other (that is, one switch at the door of the bedroom and one switch at the head of the bed, and at the same time control the light on the top of the bedroom).
