The clock turns on. The clock can run for up to a week.
Because the digital clock requires a potential of at least 1.2 V, the pair of zinc-copper cells must be connected in series. A zinc probe has been soldered to one of the leads from the digital clock and a copper probe has been soldered to the other lead. These probes are inserted into the fruit or vegetable of choice roughly 1.5 inches apart. A jumper wire that is soldered to pieces of zinc and copper metal is then inserted into the fruit or vegetable so that the zinc end of the jumper wire is 1/4 inch from the copper probe from the clock and the copper end of the jumper wire is a similar distance from the zinc probe from the clock.
The resulting zinc-copper cell can be inserted into a variety of fruits and vegetables to determine the presence of electrolytes.
An NSF funded Project