How Do Touch Lamps Work?

A touch lamp will make a beautiful addition to any room helping set the mood and providing functional lighting. For years we had to contend with switches to turn lights on and off, but no more, not since the invention of touch technology. So how do touch lamps work?

Both are a type of switch. The traditional switch that needs to be pushed, flipped, or turned is a mechanical switch and the action on the switch causes the connection to be made or broken. This type of switch has been around for years and is fairly resistant to damage.

Touch switches are sensitive to human touch a technology that's been around for years in a variety of forms. Temperature has been a common activation element for many types of switches other than lamps.

The human body is usually warmer than the surrounding air so it can be used as a trigger point. Exterior lights come on when they sense the heat of a human body, touch lamps turn on when they sense the heat, and security technology uses heat, even buttons such as those found in an elevator can be heat sensitive.

Touch sensitive lamps actually use another property of the body called capacitance which is the capacity of an object to hold electrons. The lamp has its own capacitance. For the lamp to be turned on you come along and touch the lamp which changes the electrons by your body adding to the capacity. The circuit detects this change and the light is activated.

To use a touch lamp seems pretty straightforward. You touch the lamp and it comes on. Touch it again and it goes out. But actually the technology that allows that to happen is rather complicated.

Most touch lamps have three different brightness settings without the use of a three way bulb. The brightness is changed by changing the duty cycle of the power that is reaching the bulb.

There are several components that make up the touch lamp - The metal antenna, the touch sense circuit, the flip flop memory bit, the high voltage electronic switch, the low voltage power supply, and the light bulb. A touch lamp uses both static electricity and electric current.

The metal shell of the lamp acts as the antenna. The touch sense circuitry gives the antenna a positive charge imbalance and then a negative charge. This occurs repeatedly at a very rapid rate so the outside of the lamp has a continuous vibrating static electricity on the surface. The charge is too weak to spark but it's definitely strong enough that it can be measured.

The charge on the lamp remains a constant value until you touch the shell. When you touch the shell the touch sense circuitry has to then work harder because now it has to electrify your body too. You are a lot bigger than the lamp so it takes a much bigger charge. When you touch the lamp the circuit detects the higher current in the antenna which then sends a signal to the memory circuit which then turns the light on. Touch it again and it turns it off.

The pair of electronic switches in the lamp have a job which is to remember whether the lamp is to stay on or off. They are what is called a binary flip flop and are a single bit of memory just like a computer would have. They flip between on and off.

Within the lamp is one large transistor which is what controls the light bulb. The high current, high voltage switch can withstand high amounts of voltage such as the 120 volts it receives. The memory switch flips back and forth and when open it provides a signal to the main power transistor which then closes the circuit and turns the light on. When it flips the circuit is broken and the light turns off.

All of this high tech circuitry lives is a silicon chip that's no bigger than " square and costs less than $1 to build. It might be small and cheap but it certainly isn't simple!

If you want to experiment with your touch lamp a little bit. Try this just for fun. Put a bit of oil on the tip of your finger. Touch your lamp. What happens? Nothing. That's because the oil acts as an insulator so it interrupts the electrical connection.

Try touching your lamp with a plastic item. You'll see nothing happens. That's because plastic is an insulator. But if you touch your lamp with a metal object it will turn on because metal is a conductor.

Joanne is an author of Decorz.com. If you're looking for more lighting decor ideas for your home visit http://www.decorz.com.