Obtained in a 1968 Electronics World, this circuit uses transistors from the time and the sensor is a common LDR. The component values are for scales from 0.01 to 100 foot-candle.
In the figure we have the way of obtaining 220 V from two equal 110 V transformers or 230 V from...
In the figure we have an RF amplifier for tunnel diode. The frequency range will depend on the...
This circuit can be supplied with voltages of 6 or 12 V, depending on the relay. The transistor can be...