Plant soil heater (CB7964E)

This circuit was found in a 90’s 303 Circuits. The components are from the period and the heating system depends on the resistive element.

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TTL Oscillator (CB6150E)
This oscillator can generate 2 to 10 MHz signals and was found in an American 1980s documentation. The...
Power Flasher (CB18480E)
This flasher was originally intended for Christmas tree lamps. The circuit is from 1974 and uses...
Operational with Hysteresis LM309 (CB15103E)
In the figure we have the way to add hysteresis to an operational amplifier. The relationship...