The QWL
Loudspeaker
- Originally designed for ETI readers back in 1988, we present an updated
version of this Quarter Wave Loaded loudspeaker with improved drivers
and matching crossover network. It has a very small "footprint",
and its intriguing tall design means that no floorstand is required.
Practical Oscillator Designs - 4: our comprehensive hands-on tutorial series this month covers negative resistance oscillators.
PIC 16F87x Mini Tutorial - understand and use these new chips, guided by our specially-written tutorial feature.
PIC 16F87x Mini Tutorial by John Becker. First published October 1999. PDF 470k.
Micro
power supply- uses an LDO voltage regulator, provides a well-regulated 5V rail even if your battery's nearly flat!
Interior
Lamp Delay- for car courtesy lights (domelight), this PIC-powered device incorporates a lights-on alarm and a battery saver, which activates when a door is left open for more than five minutes.
Mains
Cable Detector- An effective design which detects the 50Hz "mains hum" signal produced by a buried mains cable, rather than attempting to detect the mass of the copper conductor beneath.