Simple NE555 thermostat controller circuit

The constant temperature controller has the characteristics of wide application, high precision, low cost, easy assembly and the like.
The thermostat is composed of a thermistor (thermistor is a type of sensitive component, which is divided into a positive temperature coefficient thermistor (PTC) and a negative temperature coefficient thermistor (NTC) according to the temperature coefficient. The thermistor The typical characteristics of the device are temperature sensitive and exhibit different resistance values ​​at different temperatures. The positive temperature coefficient thermistor (PTC) has a higher resistance value at higher temperatures, and the negative temperature coefficient thermistor (NTC) The higher the temperature, the lower the resistance value, they belong to the semiconductor device) Rt1, Rt2, NE555 time base circuit, temperature range adjustment resistor RP1, RP2 and control actuator, the circuit is shown in Figure 1 (click here to download the schematic ). Rt1 and RP1 are upper limit temperature detecting resistors, and Rt2 and RP2 are lower limit temperature detecting resistors. When the temperature drops, when the potential of the 2 pin is lower than 1/3Vcc, the 3 pin outputs a high level, the J pulls in, the LED 2 lights up, and the heating starts. When the temperature rises and the IC6 pin potential is higher than 2/3Vcc, the 3 pin outputs a low level, J is released, the controlled "heater" power is turned off, and the heating is stopped.
When adjusting, it is preferred to adjust the upper limit temperature, put Rt1 in the required upper temperature environment (monitored by thermometer), after one minute (Rt1 and the environment reach thermal equilibrium), adjust RP1 to LED1 just emit light, repeat multi-tone Several times, you can short the 2 feet to the ground first, so that the 3 feet output high level (LED1 is on), so that it is easy to observe the flip state. Then adjust the lower limit temperature, the process is the same as above, adjust RP2 to make red LED2 bright, and also adjust it several times repeatedly. You can short the 6 pin to the power supply Vcc first, so that the 3 pin outputs low level, observe the circuit flip state.
The circuit is preferably powered by a small regulated power supply (you can choose one according to your actual power supply technology in the station).
The circuit is slightly modified to act as an ultra (high, low) temperature alarm.