A Wire Runner

last modified 24-APR-2000

Wouter van Ooijen (



A wire runner is a very simple 'robot' that rides back and forth over (or more likely under) a piece of wire. Although it hardly qualifies as a robot building a wire rider can be a first step towards more capable robots, and it serves well to make kids enthousiastic to build one themselves, and to draw the attention of public on fares.

The rider does not need to traverse the whole length of the wire. Any suitable method can be used to make the rider reverse its direction, including attaching things to the wire. A very simple wire rider can be made from a small conventional motor that directly hangs on the wire with its shaft. The small diameter of the shaft makes a gearbox unnecessary.

My rider uses reed switches in the rider and magnets on the wire to reverse its direction. Other reversing mechanisms could for instance be a pure mechanical approach with two motors where the impact of stopping the rider would topple it over and put the other motor on the wire, or detecting the absence of motion from the current through the motor or even the physical reversing of the battery by a mechanical gadget at each end of the wire.

The picture shows my wire rider. It have kept it as simple as possible because I want to encourage the kids on the electronics club to make their own (and better!) riders.

The circuit of the wire rider consist of a NiCad accu with a 'loader circuit' (just a series resistor and LED), a motor (with two LEDs to indicate the direction), a relais that reverses the direction, and two reed switches that reverse the direction when they approach a permanent magnet attached to the wire. One reed switch energises the realis, which is wired to energise itself. The second reed switch shorts the relais coil. A series resistor prevents excessive currents during this shorting. The motor was salvaged from a cassette player.