What if you didn’t have to risk your life to disconnect the power during a catastrophic storm? That’s a question many people in Houston were asking themselves as they watched water from Hurricane Harvey and other storms surge through the streets, swell in the gutters, and flood their homes.
Among these Houstonians were engineering students [Jon] and [Cyrus Jyan]. They watched as homeowners fought to safely disconnect their homes from the power grid and said, it shouldn’t have to be this way. They designed the Flood Fault Circuit Interrupter to monitor target areas and disconnect the power automatically when a credible threat is detected.
The FFCI is built on top of existing protection schemes like GFCIs and Arc Fault Circuit Interrupters. It isn’t meant to replace them, but instead tie them together and turn them off based on input from float switches.
As floodwaters rise, an EEPROM does a lookup and compare to decide if the threat is enough to shut it down. If so, an alarm signal to a shunt trip breaker can either throw the whole system to OFF, or else switch over to an alternate power source. The system is built around a standard security panel and keypad interface that supports 12 V alarm output. We particularly like the float switch enclosures that allow water to enter while keeping out debris.
Arc-fault circuit breakers are a boon for household electrical safety. The garden-variety home electrical fire is usually started by the heat coming from a faulty wire arcing over. But as any radio enthusiast knows, sparks also give off broadband radio noise. Arc-fault circuit interrupters (AFCI) are special circuit breakers that listen for this noise in the power line and trip when they hear it. The problem is that they can be so sensitive that they cut out needlessly. Check out the amusing video below the break.
Our friend [Martin] moved into a new house, and discovered that he could flip the breakers by transmitting on the 20-meter band. “All the lights in the place went out and my rig switched over to battery. I thought it was strange as I was certainly drawing less than 20 A. I reset the breakers and keyed up again. I reset the breakers again and did a [expletive] Google search.” Continue reading “Ham Radio Trips Circuit Breakers”
My introduction to circuit protection came at the tender age of eight. Being a curious lad with an inventive – and apparently self-destructive – bent, I decided to make my mother a lamp. I put a hose clamp around the base of a small light bulb, stripped the insulation off an old extension cord, and jammed both ends of the wires under the clamp. When I plugged my invention into an outlet in the den, I saw the insulation flash off the cord just before the whole house went dark. Somehow the circuit breaker on the branch circuit failed and I tripped the main breaker on a 200 amp panel. My mother has never been anywhere near as impressed with this feat as I was, especially now that I know a little bit more about how electricity works and how close to I came to being a Darwin Award laureate.
To help you avoid a similar fate, I’d like to take you on a trip (tee-hee!) through the typical household power panel and look at some of the devices that stand at the ready every day, waiting for a chance to save us from ourselves. As a North American, I’ll be focusing on the residential power system standards most common around here. And although there is a lot of technology that’s designed to keep you safe as a last resort, the electricity in your wall can still kill you. Don’t become casual with mains current!
Continue reading “Tripping Out: A Field Guide to Circuit Protection”