Fish farming thermostatic control circuit

(1) Circuit composition The thermostat controller circuit for fish breeding consists of a power supply circuit and a temperature detection control circuit, as shown.
    The power circuit is composed of power transformer T, rectifier diodes
VD2, VD3, filter capacitor island, current limiting resistor and power
indicator light-emitting diode LED 1.
    The temperature detection control circuit consists of thermistor RT, resistor
, Rz, and capacitor C. , potentiometer RP, time base integrated circuit
1C, heating work indication light-emitting diode LED2, relay K
and diode VD1.
    (2) Circuit principle After the AC 220V voltage is stepped down by T,
rectified by VD2 and VD3 and filtered by G, a +9V voltage
(ux.) is generated and supplied to 1C, and at the same time LED1 is lit through R3.
    When the water temperature is lower than the set temperature of RP, the resistance of +RT
becomes larger. Make the voltage of pin ② of LC lower than V(1;/3, pin ③ of 1C
outputs high level, K is powered on and closed, its normally open contacts Kl and KZ are connected, and the electric heater EH is energized and works for heating. The indicator light-emitting diodes
I and ED2 light up.
    As the water temperature continues to rise, the resistance of RT also becomes smaller. When the water temperature exceeds the set water temperature value, the ② pin voltage of the IC will be higher than u, /
3. ③ The pin changes from high level to low level, causing K to be released, EH cuts off power and stops heating. LED 2 goes out.
    The above process repeats itself, which can make the water temperature constant near the set water temperature value.