Instructables


Most smart phones and tablets have capacitive touch screens. This is an impressive bit of technology that lets you interact directly with the screen using only your finger. But there is one problem with this kind of interface, messy finger foods. Nobody wants streaks of food all over their screen. One way to solve this problem is to use capacitive stylus. But you don't need to spend a lot of money on a commercial stylus when you can make one for free out of everyday items. In this instructable, I am going to share with you a few of my favorite designs for a DIY capacitive stylus.
 
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Step 1: Background Information

Picture of Background Information
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There are several different kinds of capacitive sensing. But in general, they all work by using an array of sensors to monitor the electrostatic field around the screen. When your finger touches the screen, it changes the electrical capacitance of that portion of the screen. This is detected as a change in voltage at various locations. The microprocessor captures, filters, and analyzes the data. Then it calculates the coordinates of where the touch occurred. You can read more about capacitive sensing here: http://en.wikipedia.org/wiki/Capacitive_sensing

When a stylus is used, the same principles apply. The only difference is that the stylus is acting as a conductor to transmit electrical charge between your hand and the phone. In order to function properly, a capacitive stylus must meet several criteria.

1. A conductive surface: It must be able conduct an electrical charge between your hand and the screen. If the material is too resistive or if the distance between your hand and the screen is too great, the signal reaching the screen may be too weak to be detected.

2. At least 1/4 inch wide: When filtering data, the processor ignores areas that are significantly smaller than a human finger tip. This helps avoid unintentional activation. Having a stylus that is about 1/4 inch wide will ensure that there is enough surface area to be detected.

3. A relatively flat end: Having a flat tip ensures that the whole face can get close enough to the screen to be detected.

4. A smooth surface: This will ensure that you don't scratch up your screen.

Following these criteria, you can find a wide variety of common items that can be used to activate a capacitive touch screen. Here are five of my favorite designs for a DIY capacitive stylus.
shahrie4 months ago
i think ill try rubber pad from my playstation gamepad button... the thing that touched the pcb when button pressed.
nansierra6 months ago

I live in a fairly remote part of Africa where it is difficult to purchase items such as this. A friend of mine is dying of cancer and has been unable to use his phone due to diminishing motor skills. I'm not at all handy but I followed your very clear instructions and made a sponge stylus using the barrel from an exacto knife. It works perfectly and he can now make calls and use skype to talk to his family overseas. It's made a huge difference to him. Thanks so much!

suhyun7 months ago
thanks it helped me alot especially the battery one
testing with my smartphone:
plain old metal objects aren't working for me.
but the moist sponge and batteries work well.
some anti-static bags work well, the crinkly silver-colored ones, but the pink or clear flexible ones do not.

the conductive foam that IC chips ship on also works nicely.
ChrysN1 year ago
Nice, it made one with the sponge. Works great!
acosicris2 years ago
I only have one concern about using some materials/objects as capacitive stylus. Be careful as it might damage the screen of your device, especially those knives and screws. :)

Nice tips though.