12-09-2012, 04:07 PM
FLUID LEVEL DETECTOR
[attachment=33631]
Here 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.
[attachment=33631]
Here 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.