Circuit shown in Figure 2-49. The circuit is very simple, cold PTC thermistor element, jump characteristic thermal resistance of the lamp to control delay time. Usually the del
ay time is 10 ~ 30s, such as to change the delay time, adjustable Rz, the value of C. R. Adopt a positive temperature coefficient of thermal PTC thermistor, the choice of the Curie point about 80, nominal resistance value at 20 rise when 1500,80 to several thousand Euro to several tens of kilohms. Rt and R2 is required intimate contact.