 | Author | Message | | | eric | | Posted: Wed Aug 30, 2006 8:03 am Post subject: Magnetic Proximity Switch with Toggle | | | | Site Admin Joined: 01 Jan 1970 Posts: 311 | T.K. Hareendran
This proximity switch employs a reed switch as the sensor
device and the good old CD4017 decade counter for pulse
processing. When the circuit is first switched on, the 4017 is
reset by the short pulse generated by C2-R3. This results in
the Q0 output (pin 3) being pulled high and the LED coming
on to indicate standby mode.
When a permanent magnet is held in the vicinity of the red
switch, the switch closes, generating one clock pulse at pin 14
of the 4017. This is indicated by Q1 (pin 2) going high and
relay Re1 being energized via transistor T1.
If the magnet is removed from the reed contact and then
moved toward it again, IC1 is again clocked and the relay is deenergized.
In this way a toggle function is realized. Actually, Q2
goes high (pin 4), which causes the counter to be reset via
diode D1. Since the circuit draws only a few milliamps,
almost any mains adapter with a (loaded) output voltage of
about 12 VDC is suitable for powering
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