This simple indicator circuit was found in a documentation from the 90s. Trimpots can have values between 2k and 10k, a series resistor is recommended to limit the current to the minimum setting.
We can use high value electrolytic capacitors in alternating current circuits with the...
In the figure we have the way to use power transistors as rectifiers in a source, replacing common...
This circuit can measure frequencies up to 10 kHz using a digital multimeter or the 7107. The...