Magnetic field sensitivity of PMT

Ah yes, just didn't know the C-W abbreviation.

On a PMT it won't allow you to change the individual dynode voltages or have a non-integer relationship between them. The ripple is also ghastly unless you go well beyond the 0.022u in your example which is usually prohibitive because of a lack of space. It's 3Vpp on HV4, that would modulate in like crazy.

It sure is but it all has to pass muster with the agencies. I guess for Europe I'd have to provide the warning in 18 or so languages.

For a kilovolt that can be done, above that you'll exceed the working voltage of most optos. A 5kV rated one can generally only be tested up there for a limited number of times but not operated. In the end the solution with PNP transistors consumes less real estate. And costs less although that isn't such a concern in those applications.

Hope you got there already, we are getting pounded with rain and snow right now. If your Audi has the Quattro option it shouldn't be a problem. At least they have front wheel drive which helps. I still miss my Audi. It skeeps running over there in Europe and is over 28 years old now. Chances are it'll survive its current owner.

--
Regards, Joerg 

http://www.analogconsultants.com/

The opto's photo-transistor should never see more than a few volts across it when it is between the depletion mosfet gate and source.

piglet

However, it does see hundreds of volts across the isolation barrier and sometimes in excess of 1kV. That's where problems can develop and one must not exceed the stated working voltage.

--
Regards, Joerg 

http://www.analogconsultants.com/

Not that exciting.

We were having a day hike, with Mo's relatives, on the PCT south of Boreal. We were having a picnic on a ridge above the trail when two old guys clumped by, with what looked like 100 pound backpacks. Turns out they were hiking the entire trail, from Mexico to Canada, but only in 2 week segments, and were almost done with this one, roughly midway on the trail.

They said Hi, so I yelled down "Do you want some beer?" They said "What?" so I repeated DO YOU WANT SOME BEER? at which point they scrambled up the slope. We had a cold, unopened big Chimay and some cups, which they sure seemed to enjoy, with some decent brie and sourdough. One of the guys was originally from Germany but neither had heard of Chimay. The German guy liked it so much that he asked if he could keep the bottle, and added it to his 100 lb backpack.

The PCT has gotten much more popular since that lady published her book "Wild", about hiking the trail as therapy for her neurotic life. I tried to read it bit couldn't get past all the neurosis.

Turns out that there are "Trail Angels", locals who hang out on the trail and provide food and assistance to hikers, many of whom are neurotic people who have never hiked much before. I like to think that the Chimay made us a pioneer Trail Angel.

The opposite of "microaggression" is "microblessing", a small random act of friendliness to strangers. It's fun and satisfying and almost always unexpected.

It's 20F and snowing pretty good up here right now. It's 18F at the top of Sugar Bowl with 60 MPH winds, so I think I'll type instead of ski today. Maybe shovel the deck. There's a really complex digital PLL that I'd love to simulate, and I'm trying to see if it could be done in LT Spice. Probably not. So I might have to do it brute-force in PowerBasic. Or better yet, get one of the kids to do it in Python.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Well, embellish it. Add an RC lowpass string. Add a couple emitter followers where you need them. It still has the advantage of only needing parts that handle the step voltages, not the whole thing. Mine uses a lot of 0805 resistors and 450 volt 0805 caps, less chance of Joergian sound effects.

A low-voltage phototransistor opto can be cascoded with a 500 volt depletion fet, and that could regulate a 1500 volt supply. The combo is easy to drive and will cost under a dollar. The coupler that I'm using is ACPL227, which is rated for 3000 volts RMS for one minute, but I don't know how that translates to long-term use. Bigger optos have higher ratings, like 7KV or something.

It's a Quattro with "mud and snow" tires, which look like regular tires to me but get us past the chain controls.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Nice! Can you occasionally hike the El Dorado Trail with a similar picnic basket?

A Belgian could lose his citizenship for that.

Like Lucille Ball in the movie "Long long trailer" :-)

I heard that they had real problems with overcrowding on some sections and that things got a bit messy. Probably 99% of our population will find out their physical limits the hard way if they do such a hike, with most of them being couch potatoes. I regularly find that out when taking people along on bike rides. "Whew, I think I'll turn around at the top of that hill" while it was just there to get the muscles to operating temperature for the ride.

Absolutely. Friday I traveled a long trail alone on my mountain bike and stopped at one of my trail friends, Ivan the horse. When he came over to see me he was limping. But I could not get into the front of the property to tell them because that is a gated ranch community setting. So after returning home I tried the Sherlock Holmes thing, found out the address and then where the wife may be working but they were closed for Christmas. So I wrote a letter to "The owners of horse Ivan", telling them that I think his front left leg is hurting. Yesterday they called, saying they were very surprised and moved by this.

Some ranches have their phone number at the trail. I wish they all did that. I've used that when I saw something that might be amiss. Once I found a goat looking very much lost. No tags, no brand. After a while it trusted me, even let me touch it and I walked it back to the last ranch I saw that had goats, then "trespassed" into it together with the goat and my mountain bike. Even if it was the wrong ranch at least the goat was safe, had a barn and food.

I might not embrace Python anymore in this here life on earth. So far I found out that just about anything can be simalated in SPICE, even non-electrical stuff. As long as you can somehow describe in electrical terms and cram the respective functions and input files into it. Occasionally I stopped and built a prototype when it turned out that even a processor like the i7 cound not get through there in reasonable time.

--
Regards, Joerg 

http://www.analogconsultants.com/

So does mine and there are only very few places where I can't get by without having to bridge the whole voltage range. Just the deltas since it's a stack structure. Once you have emitter followers you need to do that anyhow because you can't get small PNP's above 500V.

Do you know how much SMT land pattern rounding the CM's tolerate these days? I want to put small radii at all corners or at least the inner ones to minimize corona effects. In the old days CM's would moan and groan over such deviations from standard but less so nowadays.

[...]

Most opto datasheets are lacking in that respect. I'd only use parts if there is a stated maximum working voltage like here:

With the others one often has to ask and it can be a hassle to get it in writing (which I usually must have).

Nice. I drove my Audi with winter tires for many years because they were aso good on non-paved roads.

--
Regards, Joerg 

http://www.analogconsultants.com/

The deck is shoveled! Well, it was an hour ago. It needs shoveling again. The driveway is deep with snow, maybe more than the Audi can handle with its 3 millimeter ground clearance. SnowTech claims they will be by this afternoon and liberate us.

I got two Python books, one something like Learn Python in a Day, which was just about typing command-line stuff. The other is the size of a phone book, around 900 pages, and I'll probably never have the energy to tackle that. But the kids are doing beautiful test programs in Python, Ethernet and USB and accessing direct memory-mapped VME modules and stuff, and poking test reports into a company database for future reference and statistics. Seems like it can do anything. I really prefer designing circuits (and I'm still better at that than they are) so the division of labor suits me. They do the VHDL and Verilog and test benches for FPGAs, and the embedded C, too.

It's probably better to prototype the PLL and play with it. It will need a VCO, digital capacitor, varicap, ADC, DAC, and an FPGA, but it will run in realtime maybe 1e12 faster than any simulation.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

It was 70 degrees here today. Merry snow!

Cheers

Phil Hobbs

43F here right now, plus hail, lightning and thunder. Looks like Texas, just colder. One of our Labradors turns into a wimp when that happens.

This would be perfect mountain biking weather but then I'd be in the dog house. And we are ushers at church so I better not.

I hope John can shovel fast enough or the snow let's up since a deck can actually collapse under a load of snow.

--
Regards, Joerg 

http://www.analogconsultants.com/

20F all day, not bad really.

That's one reason to shovel it. In the great blizzard year of 2011, lots of decks and walkways up here ripped off the sides of houses. Once it packs down to a couple of feet of solid ice, you sort of have your own private glacier.

We have a warm cabin, moon boots, high-tech parkas, fully stocked Safeway down the hill. Imagine what it was like to be up here in 1850.

I want a thing like a Roomba vacuum cleaner, only it blows the snow off the deck when you run an app from your smartphone. If someone made that, I might get a smartphone.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

A friend who is in Alaska for a meeting said it's a balmy 7F.

I just bought a Ryobi Li-Ion blower which will find use in a pressure test setup. Runs 8-10 mins per battery which are swappable and charges in less than 1h. I wonder how that would work for snow. Might be too wimpy.

Or order up one of these to dump the deck snow elsewhere: We had a li'l tornado go through town yesterday. At some point I heard a sound like an airplane flying low over the house which the freighters into Mather Field often do. Except it was a bit too constant for an airplane. But I was busy soldering and didn't look outside. Later at church people told us that a Tornado came by and this time very close. Some stuff flew around but in Placerville they said it caused more serious damage.

--
Regards, Joerg 

http://www.analogconsultants.com/