| 摘要 |
PURPOSE:To enable to obtain an identical roasting state always even if roast is made continuously and the variation occurs on power source voltage, by turning a heater OFF by comparing an output of a temperature detecting device to which constgant voltage is applied by a constant voltage generating device with that of a timing device. CONSTITUTION:As the temperature in the inside of a heating chamber is high at roast after the second roast, a resisting value of a negative-characteristic thermistor 16 is declined and as electric potential of a gate terminal of a reverse inhibition thyristor (PUT)10 of an N gate 3 terminal is low, the PUT10 is turned ON and a heater 2 is made to turn OFF earlier than a previous roasting time. As a resistor 19 and the negative-characteristic thermistor 16 are kept at constant voltage by a Zener diode 20 though a charging rate of a condenser to be charged is varied similarly to a heat value of a heater 3 when the voltage of an AC power source 1 has varied, detecting capacity of the negative-characteristic thermistor 16 does not vary at all. In other words, as the charging rate to the condenser 7 is declined also even if the heat value of the heater 3 was declined also through a decline of the voltage of the AC power source 1, a period turning the heater 3 ON becomes long. An identical roasting state is obtained always in any case like this. |
