A simple comparator using an LM339 to display rough battery voltage (green/yellow/red). Still copied today in cheap voltmeters.
The unknown capacitor forms part of a 555 oscillator; frequency indicates capacitance. Calibrated with a chart. Master Handbook Of 1001 Practical Electronic Circuits Pdf
A simple comparator using an LM339 to display rough battery voltage (green/yellow/red). Still copied today in cheap voltmeters.
The unknown capacitor forms part of a 555 oscillator; frequency indicates capacitance. Calibrated with a chart.