This crystal or galena radio uses a germanium diode. C1 is an old radio variable and L1 has 100 turns of 26 or 28 wire in a 1 inch PVC pipe. The antenna must be a long wire.
This is the power supply circuit for the amplifier in the previous circuit. The source is...
This version operates in the opposite way to the previous one, triggering when light falls on the...
The sensors in this circuit are NTCs and PTCs that work in a differential way by directly...