about these touch switches I got for my lamps. With this socket screwed into the lamp socket, any metal lamp can be converted into a touch switch lamp. With my reading pole lamp, I touch any place on the metal pole to turn the lamp on and off. How could this work? The thing that puzzles me the most about this is that it works when I touch the pole with my hand (or I guess any body part) but, if I use a cloth, a paper towel, or even a metal tool of some sort (a screw driver or a ink pen) the switch does not work. Why will it work when touched with a hand but not when touched with a cloth or metal object?
8 comments:
Because our bodies conduct electricty. We have the same amount of energy in our body as a 9 volt battery. We have a current running through us but those objects do not.
well Fleta....In the 1st place I am surprised you did not know this....in the second place I am surprised you did not look this up on the net and in the third place since you did not know I am surprised you put it out there in cyber space for all to see......you need to do more crossword puzzles....
The metal shell of the lamp is the antenna. The touch-sense circuitry works by giving the antenna a positive charge imbalance and then a negative one. It does this over and over very rapidly, so positive and negative voltages appear on the metal shell of the lamp. In other words, the outside of the lamp has vibrating static
If you touch the metal lamp shell with your finger, the touch-sense circuitry has to work harder. It isn’t just sending charge in and out of the metal lamp anymore. Now it has to electrify your whole body too. Your body has a much larger surface than the lamp, so it takes a much larger amount of charge. When you touch the lamp, the circuitry detects the higher current going to the anteanna. It then sends a signal to the memory circuit below, which causes the lamp to switch from off to on (or vice versa.)
Memory bit
The lamp contains a pair of electronic switches which control each other. Their function is to "remember" whether the lamp is supposed to stay on or off. Together they are called a binary flip flop, and they act as a single memory bit just like that in a computer. When the touch-sense circuitry gives them a signal, they "flip" one way and send a signal to turn the light bulb on. When the touch-sense circuitry gives them a second signal, they "flip" the other way and tell the light bulb to turn off.
The flipflop memory circuit gives the main transistor a tiny signal, and this makes the transistor act like a closed switch. This turns on the light bulb.
Silicon chip
All this circuitry would be expensive, but it’s all reduced to microscopic size and printed into the surface of a silicon chip about 1/8 inch square. Transistors, wires, and insulators are formed on the silicon, and the chip costs less than 1$. But just because it’s small and cheap, doesn’t mean it’s simple!
Experiments
I never had my own touch-lamp to play with, but I can think of some things you might try.
•Hold a metal object in your hand and touch it to the lamp. The lamp should turn on or off. Metal is a conductor. It is full of movable charge, and it offers a path for charge flow. It electrically connects your body to the metal shell of the lamp, so the lamp "knows" that you’ve touched it.
•hold a plastic object in your hand and touch it to the lamp. Nothing happens. Plastic does not contain movable charges, it is an insulator. Plastic provides no path for charges to flow, so your body has not touched the lamp electrically.
•Dip your finger in oil, then touch your finger to the lamp. Nothing should happen. Oil is insulating. It interrupts the electrical connection between your finger and the lamp. (Don’t get in trouble for getting the lamp all oily!)
•Tape a strip of aluminum foil to the metal part of the touch-lamp. Now touch the foil. The lamp should go on or off. Aluminum (as well as all metals) is conductive, and it electrically becomes part of the antenna.
•Wet a strip of paper towel, hold the wet part in your hand, and let it touch the lamp. The lamp should go on or off. (If it doesn’t work, try using salty water on the paper towel.) The water makes the paper become conductive. If you do this with a dry paper towel, nothing should happen. Try wet string. Try wet thread
This may be more than you want to know.
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