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.
Step 1: Background Information
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.
Step 2: Metal Pen Stylus
Step 3: Battery Stylus
Step 4: Sponge Stylus
Cut off a strip of sponge that is about 1/2 inch wide and about 3 inches long. Pinch the end of the sponge and twist it into the barrel until you have 1/2-1 inch sticking out the end. Make sure that the sponge is deep enough that it makes good contact with the metal housing. Then trim the tip of the sponge with a pair of scissors and round it off. This helps make the stylus more accurate.
The only problem with using a sponge as a stylus is that it will not work if it is completely dried out. The water in the sponge helps conduct the charge. So periodically you need to rewet the sponge. It doesn't need to be soaked, just moist enough that the sponge is flexible.
Step 5: Office Supply Stylus
Step 6: Foil Stylus
Step 7: Other Materials
The head of a bolt or screw
Nails with a wide head
The inside of a zipper
A metal thumbtack
A rolled up green leaf
Wet paper towel/napkin
A stack of quarters
A freshly cut twig or stem
A pocket knife or multi-tool
The back end of a drill bit
Anything porous that is wet
Anything that is made of metal that has the right shape
This is just a short list of some materials that will work. Feel free to try out whatever you have laying around. If you think of a particularly interesting material that works, leave a comment and share.