The thermostat has a wide range of uses, high accuracy, low cost, easy alignment and so on.
Thermostat by a thermistor Rt1, Rt2, NE555 time base circuit, the temperature range adjustment resistor RP1, RP2 and control the implementation of institutions, the circuit shown in Figure 1. Rt1, RP1 maximum temperature detection resistor, Rt2, RP2 for the lower temperature sensing resistor. When the temperature decreases, the foot when the potential is lower than 1/3Vcc, pin output high, J Pick, LED2 lights, began to heat up. When the temperature of the foot due to the rising IC When potential higher than 2/3Vcc, pin output low, J release, disconnect controlled "heater" power, stop heating. Selection and production of components Parts list below.
Adjustment, the preferred maximum temperature should be adjusted to the requirements placed on the ceiling Rt1 temperature environment (with a thermometer to monitor), over a minute later (Rt1 thermal equilibrium with the environment), play a tune RP1 LED1 light just far more stressed repeatedly several times, can be first feet and shorted to ground, so as pin output high (LED1 light), it is easy to observe the flip state. Then adjust the lower limit temperature, the process above, adjust the red LED2 RP2 light, but also several times repeated adjustments, and power can be first Vcc shorted feet look so pin output low, observing the circuit flip state. Circuit power supply regulator is best to use small (according to their actual site power technology in the election system of a column). The circuit is slightly modified, can be used as super (high, low) temperature alarm.