What is a variable frequency drive? Heating, ventilation, and air conditioning systems' air supply used to be constant volume into a space. Now a variable air volume control is being used to provide ...

Reddit user [InThePartsBin] found some VFDs (Vacuum Fluorescent Displays) on an old PCB on eBay. The Russian boards date from 1987 and have a bunch of through-hole resistors, transistors and a ...