This circuit from a 1967 documentation generates 2.5 Hz signals depending on the capacitors used, in this case 160 uF. For 4 6700 pF the signal will be 20 kHz.
This circuit uses a transistor as a sensor and operates in the range of 0 to 50º C. We found it in...
This circuit was found in a Poptronics of the 90's. The components can be changed to the desired...
In the figure we have an interesting protection bridge against power polarity inversion of a...