When working on static-sensitive circuits, e.g. involving CMOS ICs, it is advisable first to discharge static electricity built up in your body. This can be done by wearing an earthed wrist-strap. Commercial straps can be relatively expensive. Here's the recipe for a cheap one using bits from your junk box.
Remove the outer cover and inner core from a ~ 15 in (40 cm) length of old TV antenna cable to leave the copper braid. Alternatively remove the insulation from one core of a similar length of stranded 15A mains flex and loosely twist the bared strands together.
Make a noose by passing the two ends of the resulting flexible conductor through a ~ 1 in (3 cm) length of plastic tube which is a sliding friction fit over the conductor.
Connect the two ends to one end of a ~ 10 ft (3 m) length of insulated 2A-5A flex using a chocolate-block connector (or crimped sleeve) of sufficient size (10-15A) to allow the flex insulation to be gripped as well as the conductors, thus providing good mechanical support for the flex.
The result should look something like this
![EarthingStrap.gif EarthingStrap.gif](https://www.electro-tech-online.com/data/attachments/61/61421-e6012125d5e264fd6350f9db91dfc05f.jpg)
Connect the other end of the 10 ft flex to one end of a 1 Megohm resistor (essential for safety).
Connect the other end of the resistor to the earthing terminal of a mains plug. Ensure that the flex is held securely by the plug's cable clamp.
It is vital that the resistor and flex within the plug do not come within 1/8 in (3 mm) of the Live/Hot pin of the plug; so either ensure their suitable positioning and insulation or remove that pin.
If desired, a crocodile/alligator clip can be connected about half-way along the 10 ft flex, for connecting to / earthing a metal chassis of equipment being worked on.
Remove the outer cover and inner core from a ~ 15 in (40 cm) length of old TV antenna cable to leave the copper braid. Alternatively remove the insulation from one core of a similar length of stranded 15A mains flex and loosely twist the bared strands together.
Make a noose by passing the two ends of the resulting flexible conductor through a ~ 1 in (3 cm) length of plastic tube which is a sliding friction fit over the conductor.
Connect the two ends to one end of a ~ 10 ft (3 m) length of insulated 2A-5A flex using a chocolate-block connector (or crimped sleeve) of sufficient size (10-15A) to allow the flex insulation to be gripped as well as the conductors, thus providing good mechanical support for the flex.
The result should look something like this
![EarthingStrap.gif EarthingStrap.gif](https://www.electro-tech-online.com/data/attachments/61/61421-e6012125d5e264fd6350f9db91dfc05f.jpg)
Connect the other end of the 10 ft flex to one end of a 1 Megohm resistor (essential for safety).
Connect the other end of the resistor to the earthing terminal of a mains plug. Ensure that the flex is held securely by the plug's cable clamp.
It is vital that the resistor and flex within the plug do not come within 1/8 in (3 mm) of the Live/Hot pin of the plug; so either ensure their suitable positioning and insulation or remove that pin.
If desired, a crocodile/alligator clip can be connected about half-way along the 10 ft flex, for connecting to / earthing a metal chassis of equipment being worked on.