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alec_t

Skinflint's Anti-static Wrist-strap

When working on static-sensitive circuits, e.g. involving CMOS ICs, it is advisable first to discha

  1. alec_t
    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
    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.