Machine-made tile humidity measurement circuit

During the firing process of machine-made bricks and tiles, the moisture content of the bricks and tiles needs to be measured. This example introduces the measurement of the moisture content of bricks and tiles. It can quickly detect
the moisture content of bricks and tiles. According to the moisture content of bricks and tiles, an audible and visual alarm is issued, which is convenient for controlling the amount of water during mixing. It also has
certain effects on artificial bricks and tiles. reference value.
    (1) Circuit composition The brick detector circuit
consists of a humidity detection probe, a regulated reference power supply, a comparator, a switching circuit and an audible and visual alarm circuit, as shown in Figure 6-39.
    The voltage-regulated reference power supply circuit is composed of resistor Rc and integrated voltage regulator 1C].
    The comparator circuit consists of integrated circuit 1C2, resistors Rz, R3, potentiometers RP1, RP2, etc.
    The switching circuit is composed of switching tube VT1, diodes VD1, VD2 and resistor wind.
    The audible and visual alarm circuit consists of light-emitting diodes LED 1. I. It is composed of ED2, resistors Rs, Rr, music integrated circuit 1C3, audio amplifier tube VT2 and speaker
Y.
    (2) Circuit principle: Insert the humidity detection probe into the brick, and the electric current value between the two detection probes will
change with the moisture content of the brick. '
    1) The water content of the birds is normal: When the moisture content of the bricks and tiles is within the allowable range, both IC2a ​​and 1C2b output high levels, causing VD1, VD2 and
VT1 to cut off, the speaker Y does not sound, and the light-emitting diodes LED1 and LED2 do not light up. .
    2) Small moisture content: When the moisture content of the bricks and tiles is lower than the lower limit of moisture content, the resistance between the two detection probes A and B is larger than normal, causing
the potential of the inverting input terminal of IC2 to increase and its output terminal to become When the battery is low, both VD1 and VT1 are turned on, the green light-emitting diode LED1 lights up, and
IC3 and VT2 work at the same time. The speaker Y sounds an alarm to remind the inspector that the humidity of the bricks is not correct.
    3) The moisture content is too high. When the moisture content of the brick is higher than the upper limit of the moisture content, the resistance between the two detection probes A and B is smaller than normal, causing the
potential of the non-phase input terminal of 1C2b to become low and its output terminal to become low. level, VD2 and VT1 are turned on, the red light-emitting diode LED 2 lights up, 1C3 and
VT2 work, and the speaker Y sounds an alarm to remind the inspector that the moisture content of the bricks and tiles is too high.