This circuit was found in the February 1980 issue of Radio Electronics magazine. The digital circuit was shown in two parts, using 20 LEDs in a configuration with the LM3914.
The configuration shown in the figure allows you to implement an debounced switch with CMOS or TTL...
Using an operational amplifier, the figure shows how to convert the waveform to low frequency...
This charger was found in the February 1978 issue of Radio Electronics magazine. The circuit is...