Touchswitch Circuit

Last Updated: 8/05/2007

Status: Currently Taking Orders

I am now offering for sale a touchswitch circuit, typically for use in lamps, but also usable anywhere else you might like to turn on/off a household AC connected device with a single touch.

Background and Overview
While working on my Prairie Desk Lamp, I decided I wanted a more high-tech method of turning it on and off than using some old-fashioned pull chain, or worse, a crappy switch attached to the power cord. I may like woodworking projects that look old-fashioned, but I don't want them operating that way too. So I looked at the local hardware stores for a touchswitch circuit, and all I found were the kind which screw into a light bulb socket, and basically require a metal-bodied lamp. That wouldn't work at all with this wooden lamp with bulbs under a shade.

So I then searched the internet for a schematic for a touchswitch circuit which I could build myself, and I found this circuit at Dave Johnson's DiscoverCircuits website. Reusing this circuit, designed by an expert in analog electronics, was much faster and easier than trying to design my own, which would have been far more complex since I'm really more knowledgable about microcontrollers and embedded systems than analog stuff.

touchswitch board

I entered the schematic into the excellent open-source PCB design program Kicad, and then used it to design a PCB. I apologize for not having a photo of this board, but it's currently installed in my lamp. I've provided the above 3D simulation drawing, generated by Kicad, to show what it looks like.

The market for this circuit is anyone who wants a touchswitch circuit to add to their own project, such as a lamp, and isn't happy with the limitations of store-bought units. If there is demand, I can also modify this circuit for other requirements, such as switching two circuits independantly, like if you had a lamp with two bulbs and wanted 3 settings: Off, 1 bulb on, and both bulbs on.

This device is shipped as a bare circuit board, measuring 2.075" x 1.000", with one 3-position terminal connector, where wires can be inserted and easily secured with screws. A hole on the other side is where the touch sensor attaches; this can be any type of metal, attached to the board with a wire.

The circuit only operates on 120V AC circuits (the standard for North America and some other countries), and can switch loads up to 200 Watts.

You may mount this board anywhere you choose, though it's obviously advisable to mount it inside something wooden or plastic to prevent any short-circuits. Each unit is fully tested, and includes instructions.

This unit is not currently in production, so I am currently taking requests to see how much interest there is. If there is enough interest, I can produce units in about two weeks. Otherwise, I can produce single quantities with a longer lead time, as it would not be difficult to add this board to my other PCB manufacturing orders.

This product will come with a one-year warranty. Since most problems lie in installation, reasonable effort will be given to assist the installer in diagnosing installation errors if a problem is reported. If the problem is diagnosed to be in the touchswitch unit, the customer will be allowed to send the malfunctioning unit back for repair or replacement, at my discretion. In this event, shipping charges will be refunded to the customer.

The price for this touchswitch circuit will probably be $25, plus any applicable shipping charges. There is no "handling" charge.

I accept payment by Paypal or by money order.

Interested? Reserve your unit now!

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