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Fluid
level detector
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is a simple but versatile circuit of fluid level detector
which can be used for various applications at home and
in industry. Circuit is built around 2-input NAND Schmitt
trigger gates N1 and N2. Gate N1 is configured as an oscillator
operating at around 1 kHz frequency. When the fluid level
reaches the probe’s level, the oscillations are coupled
to the diode detector stage comprising diodes D1 and D2,
capacitor C4 and resistor R2. The positive voltage developed
across capacitor C4 and resistor R2 combination is applied
to Schmitt NAND gate N2 which is used here as a buffer/driver.
The output of gate N2 is connected to opto-coupler MCT2E.
The output across pins 4 and 5 of the opto-coupler can
be suitably interfaced to any external circuit for indication
purposes or driving any load as desired. Use of opto-coupler
ensures complete isolation of the load from the fluid
level detector circuit. Since high frequency AC is used
for the electrodes, there is no corrosion of the electrodes
which is normally observed with DC being applied to the
electrodes. |
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