DIY Phone Cord Reuse As ESD Anti Static Wrist Strap

As an electrician, I know how ESD is a big problem for sensitive electronic components like ICs, PC mainboard, RAM, especially microchips ... The cost might be up to few thousands dollar to replace a damaged device, which is thing we want to avoid. Therefore I make 2 ESD wrist straps from old phone and it worked very well.

One of the causes of ESD events is static electricity. Static electricity is often generated through tribocharging, the separation of electric charges that occurs when two materials are brought into contact and then separated. Examples of tribocharging include walking on a rug, rubbing a plastic comb against dry hair, rubbing a balloon against a sweater, ascending from a fabric car seat, or removing some types of plastic packaging. In all these cases, the friction between two materials results in tribocharging, thus creating a difference of electrical potential that can lead to an ESD event.

A safety device used to channel static electricity to a proper ground while handling sensitive computer equipment. Electrostatic discharge (ESD) damage occurs when a release of stored static electricity travels from something such as a person's body into a conductor of a different potential, such as a computer being repaired.

ESD can cause a range of harmful effects of importance in industry, including gas, fuel vapour and coal dust explosions, as well as failure of solid state electronics components such as integrated circuits. These can suffer permanent damage when subjected to high voltages. Electronics manufacturers therefore establish electrostatic protective areas free of static, using measures to prevent charging, such as avoiding highly charging materials and measures to remove static such as grounding human workers, providing antistatic devices, and controlling humidity.

For easy and cheap solution, I'll use wrist strap to safely discharge electrostatic.

To discharge electrostatic proterty and sefety, the resistance should not to high (slow discharge) and not to low (danger when it flow through human body). A good wrist strap should have resistance between 0.9Mohm to 10Mohm. I take a small (resistant) piece from a voltage testing screwdriver and measure it. Its resistant is 2.2Mohm so I'll connect 2x 1Mohm resistors in series to make resistance of wrist strap. For example, the electrostatic is 35000V will make 0.0175mA of current through your body, which totally safe both for you and your device. It's also mean 1/4W resistors can be used.

List of things needed in this instruction:

1. Old phone cords (My cords have max length is 2.5m and 3m)
2. Crocodile clips (I choose big one)
3. Heat shrink tube
4. 4x 1 Mohm resistor
5. Soldering tin
6. Aluminum foil
7. Soldering iron
8. Stapler
9. And a cloth roll

Total cost: ~1$

First, you have to cut both end of the cord and remove the isolation. The isolation is plactic so I use hot soldering iron to melt it (do fast or the wire inside will be break).

Then put the heat shrink tube inside, then solder resistor with crocodile clip. Use more tin to make it harder to bend. Use crocodile clip to clamp the resistor (see pic).

Then cover with heat shrink tube and apply heat.

Next, fold a small sheet of aluminum foil in shape and use stapler to staple it with the cloth. The cloth length is double your wrist.

Finally staple other end of the cord to the middle of the cloth and apply solder. (Improtant)

The resistant test prove both ESD wrist strap are good and comfortable. It doesn't lose out when I'm working. Max length is 2m so it good enough for me.

With this DIY ESD wrist strap, next time you repairing your computer or pickup a sensitive electronic component, you won't have to worry about ESD anymore, just find a good grounding and clamp into it.