While we're on the subject . . . I had always thought your typical household variety motors weren't particularly sensitive to (dirty) generator power. Thus, I think it bears mentioning that modern refrigerators and home HVAC units that use the more efficient type of ECM motors are actually susceptible to damage from continued operation on dirty power. I had the misfortune of having to replace the motor on my furnace several years ago (for an unrelated reason) and was stunned at the cost of the new motor w/control unit (approx $800 wholesale).

Ye olde' induction motors will happily run on shitty power. And, that's another way to make dirty power clean, connect a motor to a generator.


Seems idiotic, but motor-generators exist. There's a whole family of this kind of device, under the general category of spinny-power-changey-things. Some of them are literally a motor connected to a generator, others are fancier and combine both functions into a single group of winding (these are more commonly called rotary converters.)

They're declining in usage as big IGBTs become more common, but at one time they were the most common way of changing single-phase into three-phase, for instance. They also used to be used to turn AC into DC at very large scales, such as to power subway systems.

Yeah, they had one of those at UCSD. Originally installed for running the Burroughs mainframe that took up 2/3 of the machine room (with the Suns and VAXen crammed into the rest of the space), they left it in after the Burroughs was removed. My impression is that it wasn't all that useful later, more of an annoyance since any time the power blinked you had to send someone down to the basement to reset it before the machine room would come back up.

And yes, most common UPSes are "standby power supplies". They let line voltage go through whenever it's there, charging a battery on the side. When line voltage goes dead they detect it and CLICK they switch over to an inverter powered by the battery. There's a short delay before the inverter comes up but the switching power supplies in a PC have plenty of capacitors in them to coast over that.

I'm a software guy, not an EE, but my understanding is that those same PC switching power supplies are pretty tolerant of "dirty" AC power because the first thing they do with it is to rectify it into DC. They really don't care about the waveform, which is why those cheap computer UPSes used "approximate sine wave" output that was really more of a stepped square wave with 5 levels (zero, the peak on both sides, and one intermediate level in between on each).

--Ian

They are still pretty common for home machinists to run old mills, shapers, etc. Almost always find them on CL under tools.

From my experience it's all about the quality of the product.
For example. Your PC power supply is probably high quality and can tolerate the dirty power. Same thing with a VFD. I've confirmed this, the shitty VFDs that come with those https://www.bigassfans.com/ can't handle a little dirty power. But once they're replaced with a high quality Yaskawa or AB unit, the faults go away. I've also experienced faults on robots that were on the same circuit as a bunch of wall mounted fans which are just low voltage induction motors. So i don't know.

We have a burglar problem.
We have been hit every night for the past week. There are a total of six "residences" in two buildings in one property - pretty unique layout.
The thieving bastards managed to get into three of them so far. I am up all night without a gun, because illegal here.
Cops politely said we are on our own.

I am looking into buying an aircraft carrier because that is pretty much the only deadly thing you can buy without a license.
On a serious note, we are seriously in some serious shit.

Baseball bats. Ambush them in the parking lot.

If nothing else, I am constantly amazed by the collective knowledge (about most anything) that exists here on MT.net . You just can't make this much shit up.

Invariably, I end up googling and learning something most every time.
Latest: https://www.hvacrschool.com/ecm-vfd-...ts-difference/

Used to be common in big transmitters as well.

At the old WLW transmitter (the 30s vintage one that made a half-megawatt output), the tube filaments were driven by motor-generators. The facility had its own power substation, so the three MGs took 2,300 volts in at ~ 30 amps (85HP) and put out 33 volts DC at 1,500 amps. And there were three of them.

https://cimg6.ibsrv.net/gimg/www.mia...62cb97ffa6.png

I got to visit that transmitter about 15 years ago. It's still there, though no longer operational.



The cooling system for that transmitter was interesting. Raw, unfiltered water ran through the tubes, and then outside the building was a large concrete-lined pond. The water was pumped up into the air (looking much like the fountains you'd see in front of a fancy hotel), and then rained down into the pond. The transmitter then pulled cooled water (and leaves, bird skeletons, etc) in from the bottom of the pond.

You're a man with endless ingenuity. I'm positive you're more than capable of setting up a booby(s) trap that makes the incapacitation of said perpetrator look like an accident.

Then you sleep like a baby.

Another suggestion...
Can of Carburetor Cleaner (B12) with the little red straw installed and a lighter makes for a VERY impressive flame thrower (about 6 feet).
Be careful of FIRE.
Big bright thief charring fire.

And best of all...
It's not a weapon!

Have you thought about weaponizing some light? My friend has 2 LED light bars on his off-road truck that are so blindingly bright, I’m surprised that they don’t shine through brick walls. Tough to steal stuff when you can’t see for an hour or 2 after having your retinas fried. Tough to get away, too.
I’ve been thinking that if I ever need to keep an intruder from getting upstairs - temporarily blinding them might be a good passive/active plan without the crap that comes with shooting them. Also would make shooting them easier, if necessary.

Thanks for all the education on generators.

I got your electrical discussion right here:


https://cimg7.ibsrv.net/gimg/www.mia...2b987a43ad.jpg

When I started shipping again back in 1986, my first ship started life as a Victory ship built in 1944. After the war it was laid up for about ten years, then modified for survey work. Ship was built with DC generators so in order to get the AC needed for various systems, we had a shitload of MG sets. I learned a lot then about how those work. Even had to spend some time sanding down brushes to work in machines they weren't meant for to keep things going (we only had so many spares, and with equipment that old it was difficult getting spares especially considering we were working within the governmental supply system).

Hakan, we have access to motion sensor lights, motion sensor alarms, and even motion sensors for garden hose sprayers used for scaring off animals. Certainly there is something creative you can do simply to scare them off with unwanted noise and attention. It need not be deadly or even painful to achieve the desired result.

Ever wanted to spend two minutes remotely operating a military robot armed with a paintball gun inside an art gallery?

Of course you have.

The event starts at 1pm Eastern time on Wednesday: https://spotsrampage.com/

Your chances of actually getting a chance to drive the robot are practically nil. But there's still a chance.

Come to think of it... Hakan, I'm pretty sure I'd abandon any plans to forcibly enter and burgle a dwelling as soon as that thing started walking towards me.

If you post it on forum.hifiguides.com, I'd imagine someone will definitely take it off your hands.

Thank you for all your creative solutions, gents.

Turns out a never seen before increase in crime is one of the unforeseeable side effects of Corona Virus. Cops told us they are overwhelmed by the sheer number of burglary cases lately.

I came pretty close to buying several bear traps and setting them in strategic locations around the property every evening. My plan was turning the bastard thief in to the cops, and handing them a separate duffel bag containing the said perp's leg.
A quick search revealed setting up such a trap carries a mandatory life sentence without parole. Also, weaponizing anything is just not allowed.

I talked to a good friend - he is the guy who builds and sells the Maxi Gauge system, and a member here - and he suggested I should talk to someone he knows very well.
This gentleman I spoke with owns a very large security firm, specializing in theft prevention and deterrence. They work with large corporations, international clients, etc.
Long story short, we spent a whole afternoon assessing the property, picking out angles and locations to cover every inch of this place with cameras and floodlights.

It is a very high tech system, incorporating machine learning and customizable and upgradable features.

Individual cameras instantly report any form of tampering or altered focus, due to natural or unnatural causes.
You can pick specific spots or areas on the screen and assign alarms for specific actions - like someone jumping over or crawling through a fence, or a part of it.
Cameras learn to identify residents, and report suspicious activity.
Each camera has a flood light, a siren and a loudspeaker, and these can be accessed, controlled and operated automatically and manually. You can talk to a cargo delivery guy remotely if you like. Or, you can activate a pre-recorded message and play that.
In the case of privacy concerns - such as a camera covering someone's window - that portion of the screen can be blacked out, even if the camera moves.
The system earmarks suspicious moments, as well as any movement in the covered area, so you do not have to waste time checking the screen if you have to rewind the video looking for a specific event.
Up to 32 users can simultaneously access and use the controls using any device with a screen and internet connection.
All wiring is protected in very strong flexible steel sheathing, and cameras cover each other (overlapping coverage).

Crews will be installing this system in the next few days. I will certainly sleep better then.

I also bought a large case of pepper spray in pocket size cans and handed them out to everyone living here. We keep about 10 of them all over our place, I even have one in the car.

Such a system will allow us to deliver actual evidence to law enforcement. Since the cops know all criminals by name, a high resolution video provides everything they need to go and pick them up. That is how the system works around here.

That's also how the system works around here.

Except when the criminals are peacefully protesting by setting fire to mixed residential / commercial buildings downtown. Then, nobody knows anybody.

Doctor: You have five minutes to live

Patient: Puts on headphones, turns on
Doctor: But the song goes for 10 minutes...

God: LET HIM FINISH!