Data Sheet

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55. Backup Switch
Build the circuit as shown on the left and turn on the switch (62). Press the
press switch (61) or touch the reed switch (83) with the magnet (7) and
you will light up the heart LED (69) and the star LED (70) at the same time.
This circuit could simulate having a backup switch, where if for whatever
reason reed switch (83) stopped working, you could still use the press
switch (61) to turn on the LEDs.
56. Fluid Level Detector
Build the circuit as shown on the left and turn on the switch (62). Press the
press switch (61) or touch the reed switch (83) with the magnet (7) and
the heart LED (69) and the bi- directional LED (71) will be turned on with
red light, while the star LED (70) is also on.
Reed switch circuits can be used to detect uid levels for coffee makers,
dishwashers, washing machines, and water heaters. By putting a magnet
on a oat, which rises and falls with the liquid in the container, the magnet
can trigger a reed switch circuit that turns on a warning light whenever the
liquid, and by extension, the magnet, reaches a certain level.