We found this circuit in a 1971 documentation. The circuit can be assembled with more modern transistors such as BC548 for Q1, BC558 for Q2 and BD135 for Q3.
This photometer was found in an English magazine in 1981 but can still be mounted today with...
In the figure we show how to use a 555 to control an SCR or another type of thyristor. Resistors R1, R2...
The circuit was originally designed to operate with MSX microcomputers in 1988 but can be used to...