This circuit was found in an old GE manual. It uses a thermocouple as a sensor. The SCR must be in accordance with the power of the controlled load.
An interesting timer is shown in the figure, using one of the 4 NAND gates of the integrated 4001....
General Electric suggests this circuit in a 1980s documentation. The operational of the time is...
This simple adjustable source uses a PNP transistor that can be the BD136 for even slightly higher...