electric heater circuit

Electric heater is one of the household appliances that people use to keep warm in winter. The temperature controller circuit of the electric heater consists of a power supply circuit and a temperature detection control
circuit, as shown in Figure 1-32. This circuit can monitor the temperature of 1 to 7 rooms. When the temperature is lower than the set temperature, the electric heater will automatically heat up
. When the temperature reaches the set temperature, it will automatically cut off the power and stop heating.
    (1) Circuit composition 220V AC power supply is stepped down by Tunlian transformer T, bridge rectifier (VD1-VIX), filter capacitors Ci and cz and
7812 three-terminal voltage stabilizing integrated circuit IC1; 12V DC voltage is output at the G terminal as The working power supply of the temperature detection control circuit.
  The temperature detection control circuit consists of seven sections. The LED digital driver is composed of integrated circuit IC2, electric hot spot thermometer Pl-P7, and anchor electrical appliance K1-K7
. Pl and Kl are used to control the room temperature in the first room, P2 and K2 are used to control the room temperature in the second room...P7 and K7 are used to control
the room temperature in the seventh room. ,
  (2) Circuit principle
  1) When the room temperature is lower than the set temperature. When the room temperature is lower than the set temperature, the temperature control contact in the electric hot spot thermometer is in a disconnected state, and
the relay corresponding to the electric hot spot thermometer is in a release state, and its normally closed contact switches the working power of the electric heater to When turned on, the room temperature starts to
rise. When the room temperature rises to the set temperature, the internal transistor of IC2 is turned on, causing the relay to switch off, its normally closed contact to disconnect, and the electric heater to stop
working.
    If the room temperature in the first room is lower than the set temperature of Pl, the temperature contact inside Pl is not connected, the ① pin of IC2 is at the level, the
high-power transistor connected to this pin is in a cut-off state, and the @ pin output is low level, K1 does not pull in, and its normally closed contact turns on the working power of the first electric heater ( not shown in the circuit ) to start heating.     2) When the room temperature exceeds the set temperature. When the room temperature rises to the set temperature of Pl, its internal temperature contact is turned on, causing the ① pin of IC2 to become high level. The transistor connected to this pin is turned on, and the ⑩ pin outputs a high level. Kl pulls in, the first electric heater is powered off and stops heating. When the temperature drops, the fork repeats the above process. This goes on and on to keep the room temperature constant at the set temperature value of Pl.