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Silent Generator – completion

Silent Generator works.

Step 1: prepare the connector. If you can’t procure one of the connectors, and they’re probably proprietary, then you could carefully stuff some 1/4″ spade connectors into the connector on the back of the UPS. Probably. Might have to make a tool, or use a small screwdriver or something like that. But anyway, strip the wires, trim to length, and then attach the connectors.

Feel free to cringe, because I used connectors for the wrong size wire. I also soldered them instead of crimping, but since they were the wrong size they weren’t going to crimp right anyway, and then especially given that I used solid wire instead of stranded. Potential Fail all around.  But all is well that ends well, so:


Then all you have to do is wire it up (the long white wire connects the two deep cycle batteries in series to give the 24 volts that the UPS needs, and then connect the other end of the new cable to the batteries.


And there you go. In initial testing it ran a 200W incandescent light bulb for ten hours before I got bored and turned it off. The batteries still had gobs of charge in them.

Speaking of charge – the UPS will recharge the batteries when the power comes back on. It’s a trickle charger and will take a couple of days to top them off, but it’ll do it. I think in a power outage it would be faster to unhook the batteries and do a quick, partial charge with jumper cables and a vehicle. There’s some anecdotal evidence that my Prius will provide 12V at about 40A, max, with the A/C and headlights turned off. The 201V battery in the trunk, and the engine-driven, three-phase alternator that charges it, can provide 21KW of power and requires requires a really big UPS as an inverter.

Speaking of “Silent” – it won’t be until you crack the UPS case open and remove/disable the beeper element. Otherwise you get a warning beep every 35 seconds or so, which is worse than listening to the generator.


Silent Generator – the Molex UPS power connector

The APC “Back-UPS RS-1500” UPS has an internal pair of batteries and a connector for an external pack to extend the runtime. The connector is (a) pretty big, and (b) not evidently something you can just go out and buy. Fortunately, I also had a totally dead identical UPS. The internal and external battery connectors are, mercifully, the same. So I just removed the dead built-in battery and snipped off the connector. There’s one on eBay right now for $15, so if you can’t get a second UPS then you could probably still get along.


The connector on the right is the one you need, the one on the left is what you’ll encounter on the back of the UPS.


From outside-edge-to-outside-edge, it’s 1.5 inches. The Molex part number is 870-1953A. That won’t match anything at Molex’s web site, or Newark for that matter. Google comes up dry… I suspect this is (semi-)custom for APC. The shape of the connector on the inside makes me think you could probably get away with 1/4″ spade lug connectors, but that makes me nervous thinking about it.

Anyway, paraphrasing John McClane, “Now I have the right connector. Ho ho ho!”

Silent Generator – Power Through Outages with a Big UPS

It seems like, between deregulation of utilities and global warming, the electrical service just isn’t as good as it was in the past. Four-day outages have become the New Normal when freezing rain comes. Of course, I bought a generator. It makes 3.5KW and is just enough to run the electric water heater, or practically all of the other appliances I have. Including, thank Spaghetti Monster, the coffee maker.

There are only two problems with the generator. The first is the storage problem. I have to keep 10 gallons of gas handy, and the stuff has a short shelf life these days. This means rotating the gas. Every couple of months I fill up the car off of the cans and then go out and fill the cans back up. Not the biggest deal, but a pain none the less. The second problem is having to do the bi-monthly generator test. I skipped that step for a while, and as soon as I needed the rig again, the carburetor had to be cleaned out. When I run the engine I always run it out of fuel before I put it up. Turns out, that isn’t good enough. You have to actually remove the float bowl, drain it, and dry it. That’s more trouble than I want to go to, so now I once again just run it every couple of months.

The second problem with the genny is the deafening roar. Now, this is where I could have been clever and gotten one of the inverter-type sets with a small, variable-speed engine. The alternator on those doesn’t even try to produce 60 hertz power, but instead the engine speed is matched to the load at the most efficient point. The strange-frequency power is rectified to DC and then passed through an inverter to turn it back into 60 hertz AC. Net result is a fairly quiet rig. They also seem to top out at about 1KW.

What I really want is a dead quiet way to power the essentials through moderate-length outages – maybe a few hours. We occasionally have these sorts of outages, though the big four-day dealies are just as common. What I really need, in other words, is a battery bank and a big honking inverter.

Cheap way to get a big honking inverter – score a dead uninterruptable power supply (UPS). The cheap ones, which is what I have, normally just pass the 120V line voltage through the unit while they tap just a little bit of power to charge a pair of small batteries. The batteries are typically 7 or 9 amp-hour gel cells, which are basically like motorcycle batteries. These batteries will eventually dry out and fail. When they do, it’s just about as cheap to replace the UPS as it is to fool with new batteries. Hence, there’s a good supply of these UPSes in the electronics recycling bins at the dump. I selected a 1.5 KVA model, though that rating is a bit ambitious. In really, it’ll provide 800 watts into a purely resistive load, like a light bulb. Or a coffee maker. Just sayin’.

You ever notice those safety lights up in stairwells, the ones that switch on a couple of lamps when the power goes out? Turns out fire codes require them in commercial buildings. Something about not trying to evacuate a crowded building and suddenly having it go dark in the stairwell. Those safety lights use the same kind of batteries as a UPS.

No, I didn’t rob them out of the safety lights. What I did was wait until the health and safety guy came around and replaced the batteries. Again, fire codes are your friend. The batteries are required to be replaced every two years, well ahead of when they should fail. All you have to do is (a) be actually friendly with the guy and not be a jerk, and (b) offer to carry those heavy things so he doesn’t have to. Four stair wells, five floors, and now I have twenty of them. I also have the dregs of a spray can of fake smoke so I can test the smoke detectors without holding candle under them,. but that’s a whole separate thing. Thanks Safety Dude. You know who you are.

I use the gel cells for all kinds of stuff. They’ll run a boom box at a drive-in movie. They’ll run a small ham rig at field day (takes a few of them to run for 24 hours, but then again I have 20 of them, so…) and they’ll run a 12V RV fan while you’re on the air.

Some of the batteries are in better shape than others – I’m guessing the two year replacement cycle was determined empirically. So I tested some of them and found the two best ones. Test rig is a 12 volt, 50 watt incandescent bulb for RV use. This works out to just about 4 amps. I put the multimeter in series with it, set to measure amps, just so I could keep an eye on discharge. I left the thing glow for an hour or so just to satisfy myself that the batteries weren’t completely ready to fail.

So now I have a UPS that will just barely make one cup of coffee. Next step is to solve the runtime problem. Hint – this involves larger batteries.


Exposure and white balance is totally blown – I used the small waterproof Olympus. It’s surprisingly good, but it isn’t perfect.

Making Loki’s Glow Stick of Destiny for Halloween

I can’t believe I didn’t post this about 5 months ago…

After Halloween quasi-cosplay as Tony Stark (stylish black T-Shirt and Arc Reactor) and as Phil Coulson (dark suit, dark tie, S.H.I.E.L.D. identification badge clip), it was time to give Loki a shot. The essence of the character is (a) tons of hair gel, (b) the sceptre, aka The Glow Stick of Destiny, and (c) Tom Hiddleston’s wit, charm, and sexy good looks.

So, two out of three ain’t bad.

The sceptre’s general shape is surprisingly close to that of an axe handle. The blade is your generic “this is a fantasy weapon with sharp bits and swoopy bits and it’s wildly, totally impractical for anything but being a movie prop, and we don’t care” aesthetic. In other words, I’ll freehand something out of thin plywood. Finally, there’s the small matter of the actual glowing crystal. Is it an Infinity Stone? A chunk of one? A magically / metaphysically charged symbol of Thanos’ grand ambition and utter evil? It looks cool, so really, who cares?

Off to the Big Box Home Improvement Store. Axe handle? Check. Spray paint? Yep. Infinity Stone? Maybe I can find a clerk.

Infinity Stone has been located, cleverly disguised as a drawer pull. Check and mate.

Back at the Secret Underground Laboratory, the process is pretty direct. Cut the threaded end off of the “crystal” drawer pull, grab a one dollar souvenir flashlight from the junk supply, and cut four layers of translucent blue plastic out of a Pendaflex-compatible folder label cover. Stack the filter material on top of the flashlight lens and then superglue the drawer pull to the top of the stack. Instant blue glowing crystal. Perfect.


Ingredients, and Finished Dish

A little bit of bandsaw work on the “blade”, then spray paint the handle Rustoleum “Metallic Vintage Copper” and the blade “Metallic Matte Nickle”. Let dry, assemble (oh, yeah – drill the clearance hole for the flashlight first) and you’re ready to take on the Avengers. I decided to go with the “Loki at the Opera House” look (dark slacks, tie, and vest with a long coat, because I didn’t find an opera coat in any thrift stores around here). Add about four ounces of super extra hold hair gel, and I have the slicked-back aerodynamic look I was going for.


Glow Stick o’ Destiny, with supplemental reading materials

After action report: Vintage Copper is too dark. I probably should spray it again with plain old gold. The scarf that Loki wears at the Opera House is essential to conveying the character. I felt like I looked the part of a nicely-dressed dude walking around with a glowing axe handle more than Thor’s mischievous adopted brother. And finally, I have to admit: Halloween is more fun in iambic meter.


Seriously, if I worked out more and grew my hair some, I could so totally look like Hiddleston…

Also – getting a usable combination of (a) decent white balance with (b) not completely blown out bright areas is proving somewhat challenging on the waterproof camera, and the new WordPress editor really does suck.

Someone check the doorbell…

My house was built in 1929.  The doorbell is presumed to have come later, but maybe not much later.  It had been getting a little unreliable the last few years (!!!) but it all came to a head two weeks ago.

Anyway, the first step to healing is to admit you need to disassemble the thing.


And a detail of those switch contacts:


So, those machine screw ends are shorted together when the doorbell button pushes the brass spring down onto the (corroded) ends of the screws.  Repair methodology: file the metal parts until they’re shiny and new looking.  The material that the threads screw into is about 50 laminations of plain old paper.  Amazingly, it has held up through at least sixty years of outdoor use.

Wire Lights

For an upcoming project (hint: the big reveal will be April 25th, but you’ll get a good glimpse of it here before the Big Day) I need a whole bunch of LEDs I can put onto some fabric. The traditional solutions have problems.  Typical “flexible PC board” tricolor LED strips are too stiff and too expensive.  A ton of discrete LEDs is too time consuming and, except at surplus prices, way too expensive.  Enter “Wire Lights” – two parallel strands of copper bell wire with surface-mount LEDs soldered between them.  Wired in series with the entire strand is a series dropping resistor sized to make the whole string light up at 5 volts.  Specified current draw is 1 Amp, but I’m going to need to measure that.  Not really visible in daylight, but they show up well under “normal” indoor illumination and they’ll be great in a slightly dimmed exhibition space.  Hmm…


Controlling a Dollar Store Solar Dancing Elephant

By now you’ve almost certainly seen those little dancing toys that move when their solar cell gets illuminated. The things fairly well litter the “everything in here is yours for just one stinking dollar” stores. I’m not going to disparage them as toys – to be honest with you, I think some of them are pretty entertaining.

Then again, when have I ever not dismantled one of my toys?

The goal here is to take a solar dancing elephant and hook it up to a computer. When something interesting happens in reality, the elephant starts wagging its ears up and down. I had thought about using it as an email alarm, but that’s just depressing. Instead, I think I’ll scrape the current weather off of the NWS and make it dance in response to something like temperature or rainfall rate. Elephants should get excited when I rains, I guess.

Step one is to crack the elephant open. What really bothers me is that some day, someone is going to arrive on this page after they googled exactly that phrase. Crack the Elephant Open. The mind boggles.


Anyway, with your elephant nicely bisected, note that the solar cell and some electronics are in the top half of the shell, and the lower half of the widget is all moving parts. The ears are pretty finely counterweighted.  It doesn’t take much force to get them moving. This is a good thing because that solar cell isn’t going to make a lot of power (milliwatts, maybe? ) and the electromagnet that it operates isn’t very big. Incidentally, the astute observer will note that there is a tiny, tiny bare die chip under epoxy on the circuit board, and that the coil is connected to it through something that looks like 40ga wire – aka “man! that’s some awfully fine wire there!” So do be careful.  If you break that wire, you’re pretty much out your one dollar.


Next step – clip the wires right at the solar cell (red one is positive, natch) and connect a long-ish two conductor wire to each of the leads going to the board. This is what you need to power your elephant. The cell on there makes about half a volt, but I’ve put five volts across the circuit with no ill effects. Evidently, the design has some wide tolerances. 🙂

Final step – connect the wires to the ground (pin 18 was as convenient as any) and to a data pin (pin 2 is the least significant bit) on a connector for a parallel port. I added a parallel 100 ohm resistor that I really didn’t need, but I figured it might help the elephant live longer. Then finally all you have to do is find an old-school laptop with a parallel port and plug it in. A few lines of C, and voila!  You’re (announcer voice) controlling elephants from Linux.  And seriously, once you’ve done that, the rest of your day is going to be all downhill.


Controlling things comes down to manipulating the parallel port (and no, this will not work through a USB-to-Parallel converter).


void main(int argc, char **argv){
unsigned int value=0;
if (argc > 1) {


int port=/*  0x378 */ 0x3bc;
int res = ioperm(port,5,1);  /* allow access to io port plus next 5 addrs */

And that’s all there is to it.