Looking for pulse-rated zener.

Western houses don't eschew basements... it just requires blasting... the ground here at my location is layered rock.

The son's always ask, "Dad, What'd you like for father's day?"

I always reply, "Dig me a wine cellar."

Then they grimace ;-)

...Jim Thompson

The same thing would happen with the simpler RC snubber accros a single switch as was sugested before, but put a diode in series with the inductor so that when the current stops the diode blocks the voltage acros the capacaitor cuasing curent in the reverse direction through the coil.

when the switch opens the current travels through the resistor and (discharged) capacitor, initialy creating the necessary voltage accros the R, then when the curent drops the voltage acros the resistor falls and the voltage accross the capacitor has risen keeping the voltage high enough all the time the curent is flowing for a fast fall time/peak voltage, when the switch next closes it discharges the capacitor through the resistor as it turns on the curent to the coil.

o | | C| C| coil C| | | V diode - | ____ +-----|____|----+ | | | D | ||-+ --- ||

And land is cheap (compared to the East). My living space is 3650 sq.ft. on a single level.

...Jim Thompson

Yeah, Win, But you then have the expense of digging it, instead of just leveling out the site and digging a little trench for your foundation. When most houses are built as part of big developments, they make it as cheap as they can.

Also, they have what they call Grading Permits, and it gets a lot more expensive if you have to move more than a yard or two of earth for your lot...

Charlie

For sure! Half-again on a 2-storey and modern basements are very useful (unlike the dungeons of old).

Best regards, Spehro Pefhany

Yes, but here in the North and East we have to dig down past frost for a foundation anyway. It's cheap to add the basement, once the hole is there. In the South and West one doesn't worry much about frost, so it's usually cheaper just to add the space on the main floor. Those areas of the West that do have frost often have basements.

Yes, but watch out for mold. I already had exposure to mold before I moved to Ottawa, but the house I moved to had a great deal in the basement and in the carpets throughout the house.

I inspected it before signing the lease, but didn't spot the mold. It was the same color as the concrete and only grew about 1/2 or 3/4 inch high. The only way to see it was to shine a flashlight parallel to the wall and look into the beam.

It seemed harmless at the time, but it completely destroyed my health for years. I am only now learning how to overcome the effects.

The family with a baby girl that moved in after me got very ill, and a neighbour and her son who lived in an identical home with the same problem also got very sick. The problem is you don't realize how much damage has occurred until it's too late.

The landlord denied any responsibility, of course. And it would be impossible to demonstrate to a jury how the mold made you sick. A good attorney would rip your argument to shreds.

So don't make the same mistake we made. If you have any indication that mold is growing in your home, don't ignore it. Take it very seriously - it can ruin your health. You would not believe how easy it can happen.

Mike Monett

^^^^^

Plurals do not use apostrophes, except some acronyms.

One question, Mike. Did the house have a good gutter system, with drainpipes, to keep roof drainage away from the basement walls?

It's the difference between tornadoes and earthquakes. In tornado country, you hide in the basement while all of the debris (cows, cars, water heaters) swirl about in the aether - in earthquake country, you go outside and watch your house collapse onto the slab.

After the earthquake, you get a front-loader, scoop up the debris, and toss it into the landfill. After picking out the kid-pix, of course.

After the tornado, you have to bail all of the water out of the basement, and hire a crane to haul up all of the house debris to ground level, and then you _still_ need to sort out the debris to figure out which is whose.

Now, the recent landslides introduce an entirely different variable into that equation - does that make this a three-pronged thing? Earthquake vs. Tornado vs. Landslide?

Then again, can't forget volcanoes, hurricanes, and tsunami! ;-)

Ooh! And Meteors! There's Meteors! And Asteroids! And Gamma Rays!

Damn! We all gonna die, might as well get high. %-}

Want Some? Rich

Gawwwd! I thought I had all your persona killed. Plonk!

...Jim Thompson

Not in a microsecond or shorter (the time in question). Then it's stuck in the few microns outside junction.

Very astute question, Win. The drainage was very poor. The gutters were full of leaves and warped so they wouldn't drain properly, and water just spilled over in the middle. But you don't notice these things until the first storm, after you have signed the lease and moved in.

The downspouts were normally connected to drainage pipes to take the water away from the house, but these had been removed to make cutting the grass easier. So the water stayed along the exterior walls.

The basement wasn't sealed - the concrete was bare. After the first storm, there was several inches of water in the basement. A great deal of wood that was stored lying flat on the floor turned out to have mold underneath.

The landlord promised to fix everything but it never happened. Then winter set in and it became impossible to do anything. Ottawa had an extremely low vacancy rate at the time, and the landlords could get away with anything. You counted yourself lucky if there was a roof over your head. Some of the places I looked at were just incredible.

All these things were against city code. But lack of enforcement meant doing the best to try to fix things myself. This turned out to be impossible. An amateur with a paintbrush cannot seal a concrete basement. It takes professionals with the proper equipment, and it should have been done when the house was built.

I tried to leave as soon as the first symptoms started, but a vacancy rate of 0.3% in the middle of winter meant there was nowhere else to go.

My big mistake was underestimating what mold can do to your health. The worst symptoms didn't really show up until after I moved. By then it was too late.

Since then I have found many basements that are sealed properly but may have accumulated cardboard boxes full of paper or clothes. Even if the basement doesn't leak, the cardboard accumulates moisture and provides an excellent place for mold to grow.

So if you can smell a musty odor after returning from shopping, mold is growing somewhere and it should be corrected.

Mike Monett

Yes, there was a sump pump. I believe the hole was 3 or 4 feet deep. The pump didn't work, and the hole was plugged with silt. I fixed both problems, but the first storm overwhelmed the pump and the basement flooded.

This was a clear sign something was wrong. But with the low vacancy rate in Ottawa, there were few places to move to. And the places that were available were in much worse condition!

Mike Monett

Astro-popes, certainly, if you wish.

Well, some areas of the coutnry have to have basements because of the tornadoes. But here in So. Calif, we seldom have basements, I'm guessing the reasons are:

Because the dwelling is on a sandy soil that has a shallow water table, so the basement would be easily flooded.

Because most of the housing built after WW2 used a poured cement slab for the floor.

Because in a bad earthquake, the rest of the house would fall into the basement.

Because it's cheaper to build a second story out of wood than dig a hole and pour concrete walls, needed for earthquake reasons. Also since it doesn't get cold here, the insulation doesn't have to be that great, so the second story is even cheaper.

Probably a combination of the above.

I think that this place has a cool basement.

Yes, that's good. One must be careful not to select R too small, because then the FET's current at switch-on might be excessive. And one musn't selecting R too high, because then it'll develop too much voltage from the inductor's current at switch-off, forcing us to use an artificially-high-voltage FET. Selecting R so its maximum voltage drop equals the maximum capacitor voltage sounds promising.

Applying this to Mark Becker's 8uH 15A 1us shutoff requirement, with C = 33nF and R = 7.5 ohms, we get a snappy 0.7us coil-current switch- off, a maximum FET voltage of 190V, and a maximum FET current of only 19A for 0.5us at switch-on. The coil is slow to get up to its 15A current, saving the FET any extra stress.

We need a high-current diode rated for more than 200V. I used both halves of a MUR3040, but despite being a fast-recovery part it still suffers from a reverse-recovery-time delay. This means the inductor rings badly (at 4MHz, 380Vp-p in my model) unless its damped. Adding 0.01uF plus 150 ohms in parallel does the job nicely, and also reduces the FET's Vd-max to 180V and Id-max to 18A.

One big downside to this approach to capturing the inductor's energy is another 15W of power continuously dissipated in the series diode.

An "ugly" 1000V FET like the IRFBG20 Can easily swithc on and then off in under 0.5uSec, so what is the beef?

That is acronym's if mis-spelled the way all of the other crap is mis-spelled (CD's, DVD's, CPU's etc etc & etc aka Yul Bynner the King and I).