One of the bimetal thermostatic control circuits

Using the bimetallic sheet of the fluorescent lamp starter,
a temperature sensing element can be made for constant temperature control. Using bimetallic
sheet as the temperature sensing element , the circuit is simple and easy to manufacture, but the temperature control accuracy is poor.
    The circuit is shown in Figure 11-39. When making the temperature sensor (bimetallic sheet)
, remove the glass shell of the neon bulb in the starter, leaving
the U-shaped bimetallic sheet fixed on the glass ball and a metal rod.
In order to control the temperature more accurately, the upper end of the metal rod should be
filed and bent, and the distance between the tip and the bimetal piece should be carefully adjusted
so that at the set temperature, the U-shaped bimetal piece is exactly in contact with the tip
of the metal rod
When adjusting , the temperature inside the thermostat should be observed . Generally, it needs to be adjusted several times.