I’ve been wanting to save some electricity on my conventional electric hot water heater. Well, ok, that would be nice, but really I’ve been wanting to save some money on it. I recently found out that I could switch my power company billing to Time-of-Use, which has highest cost during certain periods of the day, and lower cost the rest of the time. I decided to build a smart control to shut off the water heater during the peak period.
I installed a thermostatic mixing valve, so I could turn up the tank temperature to ludicrous heat (150F/65C). It automatically mixes in cold water to keep the house pipes at a safe temperature (120F/50C). This gives me more total heat capacity in the tank.
To monitor everything, I bought a Nutrichef 4-probe thermometer that broadcasts on bluetooth to Home Assistant (ESPHome BLE proxy). I put the probes on the upper half of the tank, lower half of tank, output pipe before mixing valve, and output pipe after mixing valve. I connected a 3V power supply into the battery leads (and kept the two AA batteries in parallel so it even has its own UPS haha).
The hours and time of day for peak billing vary by season of the year and weekday versus weekend, so I created a template sensor in HA that calculates what the current billing category is at any given moment.
My electrical switch is a 40 Amp contactor relay, controlled by a Sonoff ZBMINI Zigbee smart switch. The contactor is normally closed, so when it is not powered, the water heater operates normally. I turn on the smart switch to pull open the contactor, which interrupts the electricity to the water heater, for peak-time bypass. (Water heater is on a 30A circuit breaker, and draws 17A when heating, so a 40A contactor has a large safety margin.)
Since I’m also monitoring the bluetooth thermometers, if the tank temp drops too low during peak time, my automation will let the water heater operate and heat back up for a limited time. This way I ensure nobody in the house runs out of hot water, but a full tank reheat will wait until peak time is over. (So far this scenario hasn’t happened yet; tank storage has been enough to get through peak time).
I don’t know yet how much money this will save me, but I spent about $100 USD to put it together, which is a lot less than a new $1500 heat pump water heater.
It is also completely silent. I have not yet heard a heat pump water heater in person, but some reports say that they are loud. My water heater is in the center of the house, so noise is a concern.
This has now been in operation for about a week, and is working great so far. I’m waiting to see how next month’s power bill turns out.
An adjustable power supply is pretty handy for any electronics or low-voltage electrical work. I made a simple one from a readily-available DC-DC converter board called the DP30V5A-L, rated to 30 volts and 5 amps. I got it for USD $12 from AliExpress.
Here is why I broke the trim on the refrigerator. Or rather, here is what I was doing when I broke the trim on the refrigerator. Why I broke it is, well, ok, where was I?
The white trim on the white fridge had yellowed over the last 10 years. I happened to have read in the past about people restoring old ABS computer cases and video game consoles with some sort of bleaching process involving a “RetroBright” glop product, or a hydrogen peroxide and who-knows-what lethal concoction you can make in your own science lab at home. (You know those nerds and their projects! Heh heh! Ahem.) Which of course I could do, but I was feeling lazy and I wanted instant gratification.
Fortunately, Dr. Youtube quickly educated me that in these modern times all I really need is some hair bleaching peroxide cream and UV light. I already had my UV light source ready at hand, powered by my fusion reactor conveniently stored at a safe distance of 93 million miles, readily available now that IT’S FINALLY FREAKIN’ AUGUST ALREADY!! ABOUT TIME WE GOT SOME SUNSHINE!! GOSH!! Sorry, a little Seasonal Affective Disorder lag in the Pacific Northwest; now back to the story.
A short trip to Sally Beauty Supply store and $3 got me a bottle of “40 volume peroxide cream 12%” and now I’m beautiful! Er, I mean, now the trim on the fridge is beautiful again.
Slop on the peroxide cream with a brush, put it in a clear plastic bag, and sit it in the sun for a few hours. Et voila! It worked. One of the pieces was ABS, and one was polypropylene. The bleaching process worked best on the ABS, but the polypropylene worked pretty well also.
One theory is that the bromine added as a flame retardant is what turns the plastic yellow. Something sure was retardant. But regardless of the cause, the bleaching worked and it looks much better now. Just a few more trim pieces to break off, I mean remove carefully, and the fridge will look good as new. And stylin’ with its new ‘do !
I just won’t use the hammer and block of wood to remove the other trim pieces like I did the first ones. Hey, Dr. Youtube showed me how to easily slide them off. Mine was just a little stuck. Where’s that bigger hammer? The doc just didn’t clarify it was for a different model. Hmmph!
Anyways, if you have any white plastic that has yellowed over time, this really did work well to restore it; give it a try!
Oh, and the broken trim pieces? Fixed with spin welding!
I took a piece of plastic trim off of the refrigerator door, and the snap tabs broke right off. Dang it!
The piece was marked PP, polypropylene, which just can’t be glued. So I used spin welding to reattach them.
I cut a thin strip from a plastic lid marked PP and chucked it in the Dremel. Spun it up and worked it into the fillets. Friction melted it right in there, welding the tabs back on.
I put it back on the door and the tabs are holding on tight. Perfect!
The high school ceramics class had a pug mill that needed repair. The aluminum housing was cracked and the stainless steel mixing paddles were worn down.
Over the years I have accumulated a growing pile of pliers, screwdrivers, wrenches, and other miscellaneous small tools. It long ago outgrew the little toolbox I have, turning into more of a tool pile or perhaps a tool dumping ground. I needed a new, bigger toolbox. Having recently built some new toys, namely a bending brake and spot welder, I knew I needed to build my own toolbox.
Over the years I have accumulated a growing pile of pliers, screwdrivers, wrenches, and other miscellaneous small tools. It long ago outgrew the little toolbox I have, turning into more of a tool pile or perhaps a tool dumping ground. I needed a new, bigger toolbox. Having recently built some new toys, namely a bending brake and spot welder, I knew I needed to build my own toolbox.
Actually, it was the other way around. I had the toolbox idea first. I built the brake and spotwelder because I thought they could help build the toolbox. And they did.
I gave myself a challenge on this project, to make the entire toolbox from reused and recycled materials. Not because I’m a cheap bas bargain hunter (I blame my dad’s thrifty Scottish upbringing… Hi Dad!), but because I’m really one of those eco-hipster tree huggers who wants to save my wallet the planet.
I wanted to make some metal boxes and trays. I have plenty of scrap sheet metal from things like old PC cases and microwave ovens. I already built a sheet metal bending brake. Now I just need a way to fasten parts together. Something easier than drilling a bunch of holes and screwing or pop-riveting. Something less messy than soldering or glueing. Something where I can just magically zap the parts and have them stick together instantly. Eureka! Spot welding. Time to dig through Google. And the trash can.
initial assembly
The internet has lots of articles about how to make your own spot welder, so I’m not going to repeat everything here. The first article that inspired me was the spot welder on Hack-A-Day. There are plenty of other home made spot welder articles out there too.
Basic Design
The basic idea in spot welding is to send a high electrical current (amperage) through two pieces of sheet metal, which will heat them up enough to melt a little spot and stick them together (the “bead”). We produce the high current with a transformer, which changes high voltage low current from the wall outlet into low voltage high current in the work piece. The heat comes from electrical resistance. You need low resistance metals in your spot welder parts (copper and aluminum) so you can create heat in a higher resistance metal (steel). So this spot welder is really primarily for welding steel. Which is OK since that’s what the vast majority of scrap sheet metal is anyways. At least mine is. If you have access to some secret stash of cast-off titanium, you’ll have to figure that one out for yourself.
I needed a big, cheap transformer. Fortunately this is available in any discarded microwave oven. I can’t remember if my transformer came from the microwave oven left by the apartment dumpster, or the one left on the curb near the park. But you can probably find an unwanted, unloved microwave somewhere and give it new meaning for life. Or something like that.
Microwave ovens step up the voltage inside, but we want to step it down. So we remove the transformer secondary winding, with the lots and lots of turns of teeny-tiny little wire, and replace it with a few turns of big fat wire. I used a hack saw to cut off the old wire. You can try that or your teeth, but I’d recommend the hacksaw.
Wire size is dictated by the current, so we want as big a cross-section as possible in our wire. I used eight strands of 10-gauge (AWG) stranded copper wire, which the building electricians at work let me have when they were ripping out some old light fixtures. 10-gauge wire has a cross-section area of 5 mm sq., so that puts me at 40mm sq. for all eight strands. Those hot-shots in the other articles bragging about their 4-gauge wire? I got double the size. Oh yeah, who rules now, huh? HUH?!?! Oops, sorry, got carried away with the nerd contest there for a moment. Where was I?
I wound one and a half turns of the wire, which was all I could fit. Measuring with my volt meter, I found that with 120 VAC input, I measured 2 volts on the output (open circuit with no load). When welding a bead, the 2 volts dropped to 0.5 volts. And the current? Using my inductive ammeter, I measured 15 amps on the input (mains) side, and 900 amps on the output side. Let me just say: it’s awesome.
Mechanically, the design is simple. Two identical wooden arms held open by a spring. Each arm has an aluminum bar on the end, holding a copper electrode. The wire from the transformer is attached to the aluminum bar, with as much surface contact area as possible. I stripped the ends of the wires and smashed, I mean crimped, a piece of copper plumbing pipe onto the end to make a lug, and bolted it to the bar. (Actually, the first time I squeezed the pipe so tight that the side split open. The second time I got it tight enough to hold on to the wire but not split apart. No, that wasn’t admitting a mistake, that was a “design revision”. Yeah, that’s my story, yeah…)
The electrode tips are MIG welding tips, which are adequate although possibly a little short, depending on what you are doing. But they are inexpensive, which you probably know by now is one of my top criteria.
jaws and electrodes
jaws and electrodes
jaws and electrodes
My control circuit
internals
schematic
I needed a push-button switch on the upper arm, because I am all about elegance and comfort. Hold the arm down on the work piece, push the button until the acrid burning paint smoke burns my nostrils, I mean until the spot weld bead is formed, release the button, and then release the arm. (Just kidding on the smoke part; I always clean the weld area thoroughly to remove paint and contamination before attempting to weld it. Well, usually.)
internals
As far as safety goes, the spot welder is pretty safe. At a few volts, there is no concern of electrocution on the secondary output side of the transformer, the arms or electrodes. The main concern there is burning yourself on a hot piece of metal.
The primary input side of the transformer is another story. This thing works from 120VAC electrical mains, and I’m building it myself (that should scare you enough right there), so yes I’m a little leery about having high voltage right next to my finger on the push-button. My solution was to use a low-voltage control circuit. The push button operates at 6 volts, and activates a mechanical relay, which switches the 120 volt input to the transformer. I used a common “wall-wart” power adapter to provide the 6 volts. There is also a master on-off switch, for extra safety.
One possible concern with using mechanical relays is that arcing of the contacts can cause pitting and deterioration over time. This can be reduced by using larger contacts (in relays with higher amperage ratings). It can also be reduced by using solid state relays, but those cost more than, like, one dollar, so they exceeded my budget for this project. Since I knew I was drawing about 15 amps on the input side, I wanted my relay switching to be rated for much more than that, for safety and longevity. I got two double-pole relays rated at 12 amps, and wired all 4 poles in parallel. This gave me 48 amps nominal rating, which is safely far beyond my expected usage of 15 amps.
I added one more minor complication to the control circuit. I did not have any mechanical relays with low-voltage (6 volt) coils and high-voltage (120 VAC) high amperage (10+ amps) contacts. The only relays I had with high-voltage contacts also had high voltage coils, so I used another transistor-like chip called a MOC3022 opto-triac to control the relay. The opto-triac takes a low voltage DC signal and switches a high voltage AC line. The switched high-voltage AC output of the opto-triac is very low current, so it is not adequate to switch the transformer directly, but it is perfectly fine for driving the relay coil. So the push button activates the opto-triac, the opto-triac activates the relay, and the relay activates the transformer. Why make it so complicated? Well, because it was really cheap. The opto-triac cost less than a dollar, and the relays were a dollar or so also. While a solid-state relay would have been nice, it would probably have cost about 30 dollars, which is about 29 dollars more than my budget for the project.
Case
case
With live, high-voltage electricity feeding the transformer and control circuit, the spot welder needs a case to cover those parts for safety. Having been suitably inspired by “Uncle Dave” Gingery to make my tools bootstrap themselves, I knew that my spot welder needed to make its own case. I cut and bent some scraps from a PC to make a cover for the transformer and wires. Then I used the spot welder to attach the end panel of the cover. Voila! The machine builds itself! Well, partly at least.
case (and my assistant Sam)
case
spot welded its own case
Results
This thing works fairly well. I’ve mostly been using it on some salvaged sheet metal from a refrigerator door, and from PC cases. The thinner refrigerator door skin welds a good bead in 1 or 2 seconds. It measures about 0.025 inches thick (about 0.6 mm, or perhaps 25 gauge I think). The heavier PC case metal takes about 4 or 5 seconds to make a good bead. It measures about 0.040 inches (about 1 mm or perhaps 19 or 20 gauge I think).
The tips and big wires get fairly hot in use. If I weld PC case metal for 5 minutes straight, I need to stop and let the spot welder cool down for another 5 or 10 minutes. The arms themselves are wood, and remain quite cool to the touch. Wood seems to be a pretty good heat insulator.
The first real project for the spot welder (not including making its own case) is attaching the drawer fronts of my tool-box-in-progress. I’ll finish it one of these days. In the mean time, I’m spot welding!
I built my own sheetmetal bending brake. I used some scrap angle steel pieces which I welded with my arc welder.
Scrap sheet metal is easy for me to find, from PC cases and discarded appliances. But to be useful, you need to be able to bend a nice clean straight line.
The base and bending lip were easy to make. I had a little more trouble deciding how to make the press clamp. My short-term solution just bolts straight down from the top.
I built a stylish energy-efficient desk lamp, entirely from scratch. I have always enjoyed Art Deco and Machine Age industrial styling, and was inspired to use it for the lamp when my son and I were watching Batman, the Animated Series. A desk lamp worthy of Wayne Manor was in order.
The thing that originally prompted me to build a lamp was a broken computer scanner. I took it apart and removed the cold-cathode fluorescent light, and thought to myself “this would make a cool lamp”. And efficient too; putting out a lot of light at only about 5 watts as I recall.
I envisioned a long thin tube light at the end of an arm, which could be swiveled and positioned as desired over the desk. I made a shade for the tube from copper plumbing pipe. The CCFL inverter would be placed in the base of the lamp, along with a 12v power adapter and a few yellow LEDs to make the base glow.
As in most of my projects, I started the base with some sketches and then a cardboard model. I built it from acrylic plastic, cut on the table saw and bent by heating with the heat gun. I sanded it with fine sand paper, to change the gloss finish to a matte. Then I painted it with black vinyl dye.
Although it looks more like an Art Deco radio than a lamp, the result is still pretty good I think. It was just big enough to fit the 12v power supply, the CCFL inverter, a power switch and a few LEDs. Only one problem: it weighs nothing. Not good for the base of a lamp with metal arms and head. A heavy piece of steel in the bottom solved that.
I built the arm using 3/8″ chrome-plated copper pipe. The sections are connected by ball joints made from short bolts, with the heads rounded off using a file in the drill press. I first thought I needed to tap the tubes for the bolts. Then I found the copper was so soft the bolts would tap themselves.
The relatively-small contact area of the ball joints makes them somewhat weak. This means the lamp shade should be as light as possible.
First assembly
Once I had the base, arms, and CCFL lamp built, I assembled them together and soldered the CCFL bulb on the end of the wires running through the arms, to the CCFL inverter in the base. First try: Oh no! It didn’t work. The tube just glowed dimly on each end.
I checked all the connections; no help. I disassembled it and connected the tube back directly to the inverter. It worked. Huh?!?! I determined there was nothing wrong with any of the individual parts or wires; they just didn’t work together. I could not get the lamp to work with the inverter in the base, away from the tube.
Argh! Frustrated, I set the project aside for quite a few months.
Copper shade
Copper shade
light test
