1000W 12V –> 220V Inverter
instructables.comI have to admit that I really dislike using ~12V batteries for high power applications like this. I say this having built a ~400A ~14V system. It’s miserable.
1 kW at 100V or 250V or similar uses a nice, small, flexible wire. It can be quite safe because it can be fused or otherwise protected at low currents, which mitigates the risk of welding things, starting fires, or arcing. Ground fault protection, arc fault protection, and general loss-of-isolation protection are available. It’s easy to rework (lever nuts! screw terminals!).
400A (or even 80A or so like in this article) is a whole different ball game. Sure, you have to work hard to electrocute yourself. But you can easily set things on fire or weld things together without coming close to blowing a fuse. And you need to protect both ends of wires in a parallel arrangement. And the wires are enormous, expensive, and hard to terminate.
I would much prefer one of three alternative designs to become popular:
1A: a series arrangement of batteries at a civilized 48V or so. You can do this with an aftermarket BMS, but they tend to be janky.
1B: same but actually high voltage (a few hundred V, like an EV)
2: batteries with microinverters and a civilized way to share current. A manufacturer could make a single package with a 1kWh battery, a BMS, a low voltage, low current DC auxiliary output, and a ground-fault and overcurrent-protected 110-250V AC input/output. And an RS485 or 10BASE-T1S or CAN connection so that they can coordinate their I-V characteristics to appropriate distribute charge or discharge current.
Now you can connect as many microinverter-batteries as you like in parallel, using #14 wire, to one ordinary circuit breaker per battery plus (depending on the overall arrangement) one big breaker to protect the common bus.
edit: Also, with this design, no one, not even the manufacturer, needs to touch a heavy-gauge wire. Everything in the battery would use cheap, painless busbars or small wires, depending on the internal voltage, and the manufacturer could set the voltage however they like. Although 12V internally might be entirely reasonable if the end user also wants to consume 12V at very low currents through the aux output.
I use 48v for all my high power DC applications and I usually spin PCBs. Part of the reason I use 48vdc is that there are bunch of ICs and reference designs for PoE applications that run at this voltage level.
12v is a miserable voltage to work with in general: too high for most logic circuits and for LDOs to work effectively but it’s too low for any large load with high-power applications become cost prohibitive quickly due to the cost of the conductors. Fun fact: Auto makers have gotten away with under sizing starter conductors, despite it drawing 80-100A, because it is only energized briefly and the length of the run is very short.
And I think 48VDC is the highest convenient voltage you get before exceeding ELV. There are a lot of surplus telecom and server power supplies that gives 48V at decent current. Above that there is a real risk of electrical injury, at least according to regulations.
You can actually go up to 120VDC (with no ripple) before you’re out of ELV - which I always find surprising. You’re probably thinking of the A/C limit which is 50V RMS.
Interesting, I thought the limit is at 60VDC.
IEC limits are 120VDC, 50VAC which quite a few countries will use (eu*/au/nz).
US NEMA/NEC is a very different standard.
60 VDC / 30 VAC in Canada per CSA Z462 (workplace electrical safety).
Much industrial automation runs on 24VDC. High enough that the losses within a cabinet are tolerable, low enough that there's no electrocution hazard.
If you keep your hands dry or if you're a male, then 48VDC can be quite safe too.
https://www.allaboutcircuits.com/textbook/direct-current/chp...
We're running out of copper. So better keep your voltages on the high end (but still safe of course).
https://www.cnbc.com/2023/02/07/there-isnt-enough-copper-in-...
To save someone else looking for the answer to why being male is a factor here… (which I didn’t know about!)
> Oh, and in case you’re wondering, I have no idea why women tend to be more susceptible to electric currents than men!
The pain thresholds are given in a table that is split by men and women. I believe the assumption is different conductivity between “typical” male/female bodies, but it’s really not spelled out.
Yes, on one hand it's strange because body fat decreases conductivity, and women have typically larger amount of body fat (25% versus 15%).
https://www.ncbi.nlm.nih.gov/books/NBK218162/
However, men are typically larger, so perhaps that's the reason.
Soo fat people are more shock-resistant too ?
There's a push for '12vo' or 12 volt only PSUs for PCs... but with the major power consumers mostly the GPU, CPU, RAM (?), and possibly spinning drives, would a similar to telecom gear 48V make more sense?
For GPUs and any USB PD connections ('standard' is up to 20V 5A while 'extended' is 48V 5A) a system power level of ~48v might be very useful. It would also give a chance to replace the recent higher density connectors that aren't designed with a sufficiently robust user experience with improved versions that more clearly lock into solid connection.
Not really.
Pretty much the only PC part which wants native 12V would be the fans. All the other parts drop it down to 5V / 3V3 for auxiliary components, or 1-2V for the CPU and GPU cores - which use the vast majority of power.
Dropping 12V DC to 1.5V is reasonably doable, but dropping 48V DC to 1.5V is a bit of a pain. In general you do not want to go beyond a 1:10 ratio for efficiency reasons, so 48V doesn't really gain you anything, while at the same time resulting in a massive compatibility break.
The push to 12VO is driven by a desire to get rid of technical debt. The 3V3 / 5V wires can't handle the current you need on those rails, so those are converted from 12V anyways. And literally nobody is using the -12V and -5V wires, so keeping those around is pointless.
Open compute platform switched to 48V years ago, to afford having multiple PSUs feeding multiple servers, with (those days) a fixed 4:1 switched capacitor down converter right next to the existing 12V-to-0.5~1.5V DrMOS VRM power stages.
There are iirc GaN devices from epc-co these days that make it feasible to go directly from 48V with the VRMs to the 0.5~1.5V for the core.
Why does the ratio affect efficiency? Naively it seems like it should just be able to use differently sized inductors.
Yes, I thought 48vo was already on the drawing board.
> And an RS485 or 10BASE-T1S or CAN connection so that they can coordinate their I-V characteristics
Note that simply voltage/frequency alone can communicate everything necessary to evenly distribute load. For example:
Output frequency = 60 + X Hz
Where X varies between -0.1 and 0.1, indicating the percentage of max load the inverter is under(in charge or discharge direction).
Such a scheme will self synchronize any number of inverters, even of varying capacities, into a stable grid, and they will all be the same percentage loaded. The grid can even have a few dumb gas generators on too and remain stable. No fancy comms needed.
That's not simple to create with inverters alone.
Yep, inverters can easily read the frequency change to adapt their output. But a device that reads the network load and translates it into a frequency change is really not trivial. Grids do this because mechanical generators do that translation, but the easiest way to add it to a non-mechanical grid is adding a mechanical device.
Lines exclusively fed by inverters will naturally get undervoltage, instead of frequency shifts.
> But a device that reads the network load and translates it into a frequency change is really not trivial.
Nah - it's pretty simple. Have your inverter measure it's own load - for example by measuring the current through the main switching element. Compare that to the max current that switching element can handle. That is your percentage load that you are under. (negative if current goes backwards)
Then use that to decide what frequency you will output, using the formula.
There is one extra element to this... At startup, to avoid large transient currents, you need to start with the 'max switching element current' for the formula at zero, and then increase it smoothly only while the calculated load figure is under 100%. Within a few seconds you will get sync with any existing network. Such a scheme also works for blackstarting an isolated grid, or with many other inverters with the same strategy.
This scheme has a big benefit that there is no need to measure the grid frequency precisely - which is actually a fairly hard thing to do on noisy small grids.
And it turns out thats all thats required to maintain grid sync. As long as supply capacity exceeds demand at all times, this grid will be stable.
Do you have a reference?
If I followed this right, the frequency goes up with load (which seems backwards). So a 50%-loaded grid will be at 60.05 Hz. A newly started inverter will try to output 60 Hz (and fail, since it is unable to single-handedly reduce the frequency). But it will surely end up with nonzero current.
Don’t real spinning synchronous machines work the other way? If they are overloaded, they spin slower, and if they are spinning a bit slower than the grid when connected, the grid will speed them up?
By the way, the reason big national grids don't allow this scheme is because it is too stable. Ie. if your house, containing some inverters like this, is disconnected from the national grid, it will continue independantly. Your house and the national grid will continue on their own paths, with slightly differing frequencies.
Reconnecting two grids at differing frequencies is hard.
> Reconnecting two grids at differing frequencies is hard.
Indeed it is. The last time this happened in 2021 here in Europe, South-Eastern Europe split off, and it took a good hour to get everything balanced again [1].
[1] https://www.entsoe.eu/news/2021/01/26/system-separation-in-t...
> if your house, containing some inverters like this, is disconnected from the national grid, it will continue independantly. Your house and the national grid will continue on their own paths, with slightly differing frequencies.
That's not the main reason.
The main reason is that if grid is down, workers need to work on it safely and so they need it de-energized, not some random solar installation trying to feed power into it.
Some inverters for that reason have 2 outputs, one for grid, other one for so called EPS (emergency power supply). When grid goes down, usually relay disconnects the two and inverter only feeds power to EPS, and re-connects both outputs only when grid is back up and synced. So you'd shove your important loads onto EPS output and have it grid-independent.
> The main reason is that if grid is down, workers need to work on it safely and so they need it de-energized, not some random solar installation trying to feed power into it.
I’m sure this has motivated someone who makes rules, but I once had occasion to ask some actual line workers replacing equipment serving me, and they laughed. They said that they always assumed the lines were hot at both ends, and if they needed a line to be de-energized for safety, they would deliberately short it out. A pesky little residential inverter was not in the slightest bit concerning to them, anti-islanding or no.
I do believe that closing a switch between the grid and a small residential island could be unpleasant for the island or maybe even for the switch. And closing a large switch connecting an entire neighborhood that somehow formed a functional island and connecting it to the grid without synchronization might genuinely go poorly.
But mostly I think the most important current reason for anti-islanding is that a small residential or light commercial inverter is unlikely to have anywhere near the capacity to power an entire secondary circuit, nor does its owner want it to.
I doubt it would be required by law if it was just an issue of someone's inverter tripping overcurrent proteciton
> I’m sure this has motivated someone who makes rules, but I once had occasion to ask some actual line workers replacing equipment serving me, and they laughed. They said that they always assumed the lines were hot at both ends, and if they needed a line to be de-energized for safety, they would deliberately short it out. A pesky little residential inverter was not in the slightest bit concerning to them, anti-islanding or no.
Well, that's generally good safety measure.
> But mostly I think the most important current reason for anti-islanding is that a small residential or light commercial inverter is unlikely to have anywhere near the capacity to power an entire secondary circuit, nor does its owner want it to.
Many places do, hell, common problem is grid voltage being too high and inverters turning off because too many neighbours got solar. I'd imagine its pretty easy in peak to have solar exceed local demand even if only part of houses have it. At the very least "to the next transformer".
I wonder whether the move to green energy would change the way grids are build. "Micro-grid" with all houses on street connected to substation with a bunch of batteries that most of the time just stores local peak and sells it back to the residents might be an interesting idea and potentially make grid more resilient overall.
> if they needed a line to be de-energized for safety, they would deliberately short it out
An old electrician once showed me his technique for tracing a circuit in a house back to the breaker panel: open the box, expose two wires, cross them with the shaft of a screwdriver, wait for the pop, walk back to the panel and see which breaker tripped. Tada!
It might be pretty complex code wise but not cost wise, you just need to probe current and voltage, which you do anyway
I think this works for discharge, possibly with some extra cleverness needed if the batteries are at different SoCs. But I’m not sure how it could handle being tied to the grid intelligently or how charging could be managed without some additional controls.
Also, can a pure frequency-based scheme handle the case where a whole bunch of inverters are in parallel and a load that’s much larger than any one of them can handle individually starts up?
> handle the case where a whole bunch of inverters are in parallel and a load that’s much larger than any one of them can handle individually
Yes, but with caveats... The grid will startup, smoothly (ie. gradually), but during startup every inverter will be at its maximum configured load (with the maximum load config ramped during startup). When the maximum load is hit, the frequency sits at the minimum design frequency (59.9 Hz in this case), and voltage drops instead.
So your large device will see a sine wave at 59.9 Hz that starts at zero volts, and increases in amplitude to 230 volts gradually over many seconds, and as soon as it hits 230 volts, the frequency will almost immediately become 60 Hz.
For large motors, thats a problem. Large motors typically don't like line frequency at a reduced voltage - they can end up not having enough torque to turn, and will just rapidly heat up. They would do better without the gradual startup ramp - but that startup ramp is necessary to ensure the inverters stay in sync.
In reality, this scheme works for AC type motors rated up to about 30% of the capacity of the inverter set, or up to 100% as long as another motor is already running on the same grid.
> extra cleverness needed if the batteries are at different SoCs
The scheme as presented keeps the inverters under equal fraction load, but does not guarantee the batteries end up at equal state of charge. The formula can easily be modified to over time achieve this too:
X = 60 + (fraction load of inverter)*0.1 + per_battery_factor
The per_battery_factor would be set based on the batteries state of charge and/or any user instructions from buttons to charge or discharge a specific battery.
> I have to admit that I really dislike using ~12V batteries for high power applications like this. I say this having built a ~400A ~14V system. It’s miserable.
The schematic looks to be pretty adaptable to higher driving voltage, just need separate 12V for control board. There is even one in datasheet for 24-36V operation
>2: batteries with microinverters and a civilized way to share current. A manufacturer could make a single package with a 1kWh battery, a BMS, a low voltage, low current DC auxiliary output, and a ground-fault and overcurrent-protected 110-250V AC input/output. And an RS485 or 10BASE-T1S or CAN connection so that they can coordinate their I-V characteristics to appropriate distribute charge or discharge current.
> Now you can connect as many microinverter-batteries as you like in parallel, using #14 wire, to one ordinary circuit breaker per battery plus (depending on the overall arrangement) one big breaker to protect the common bus.
You can build it right now. AC coupled batteries exist; here is some random one that scales up: https://www.fortresspower.com/ac-coupled/
The problem is that you generally want batteries when you want renewables and in that case just having one big box handling batteries and solar panels is more economical than microinverters everywhere
48V battery pack + BMS is significantly cheaper than same thing with microinverter, and when you scale up one big inverter is cheaper than a bunch of smaller ones.
So yeah, it is "best" but also most expensive way. And frankly, the hardest to develop, which is probably why there is little to no open designs for that.
Depending on the load, you can often skimp on the conductors and get away with it. Someone else mentioned undersized starter power cables. There's really only a few loads that are full draw, full duty cycle.
Old car stereo trick, to power big amplifiers in the trunk: use a second battery and big power lead to it, small power leads from the main battery to the secondary. That secondary can be backed or replaced by big capacitors, too; with commensurate increases in cost and possible risks when things go wrongs. But you can provide rich chunky amps and use skinnier cable than you'd think on the long run to do it.
Never forget to put an override relay (normal open, closing when the engine has run for a set amount of time or when manually bypassed) and a fuse in the path though (and that also applies for campers). There are a number of things to consider, and if done badly, also serious risks:
- you don't want a permanent connection between the main and aux battery to avoid accidentally sucking both batteries dry on the aux-battery side, and to avoid the starter overloading the cable between the two batteries
- you don't want to risk an empty aux battery charging itself on the main battery and engine with more current than the cable supports, hence the fuse
- you do want to be able to connect both batteries in a scenario where you accidentally drained the main battery (e.g. a light left on) to "self-start"
All very good point, tx. I liked diodes as well as fuses, especially on the inputs of capacitors. Automotive power is never clean.
> 1A: a series arrangement of batteries at a civilized 48V
And here I am mad that home-storage server rack batteries are all 48V it seems, but for the same reasons (huge 400+ amp cables required to get decent wattages). When each car charger can do ~14.4kw you need a lot of fat cables running to battery banks
That's because 48-50V is threshold for "High Voltage", what THAT sign actually signifies, and licenses are required!
Technically not, actually. By the IEC standard, 50V (RMS AC) is about the highest you can go for 'Extra-low voltage'. IEC actually has DC up to 120 V as ELV but often regional standards will have a lower value (like EU seems to be 75V and Australia/New Zealand at 60V)
Only above 1000V RMS AC or 1500 V DC is considered 'high voltage'.
That's why a correct sticker on domestic equipment will usually use the wording 'Dangerous voltage' or 'Hazardous voltage' or the like, not 'high voltage'. An actual correctly placed 'Danger - High Voltage' sign tends to mean something like 11kV AC
While people are talking about use cases, I've been shopping for exactly this. My Nissan Leaf's DC-DC converter that drops the HV traction battery down to 12V (well, 14.6V-ish) to supply the regular vehicle electrics is apparently 1kW capable, as the heat pump needs a lot of power. If you turn the climate control off but leave the car on, then you can apparently pull 80A or so from the 12V "battery" perfectly fine as the DC-DC converter will keep it supplied. This is a relatively safer way of tapping into the traction battery without having to deal with the HVDC.
With an inverter, I could then supply (some subset of) my house from the traction battery, giving me a theoretical 18 hours at 1kW in my case (less efficiency losses).
> as the heat pump needs a lot of power
I don't know about leaf's specifics, but most EVs have the heat pump / resistive element wired to the HV battery instead of the 12V one.
It's hard to imagine where one could safely pull 80a from. What kind of busbar that's exposed will have that available to safely draw from?
From the main battery terminals, as far as I understand. I appreciate that this relies on the path from the DC-DC converter to the 12V battery to be sufficient for 80A sustained. Apparently this is fine, but I have yet to look myself.
An ICE car can have the battery supply ~200A through that cabling, though of course that's burst and not sustained. But it does suggest to me that it's not out of the question - especially as it's normal in the automotive industry for some cabling to carry such high currents for this reason.
I don't like the design of the voltage feedback circuit here.
It couples the AC side to gnd, and does so through a 100k resistor, which is barely safe (and in my view, any AC that is coupled to gnd isn't sufficiently safe unless it also has leakage detection).
It ought to use an optoisolator or even better have leakage detection, which isnt hard to implement in circuits like this.
This is one of those "if you don't understand all the words in the article then you should not be attempting it" articles.
But it's still fun to read :)
It's definitely "just buy one", if you just want an inverter.
It is nonetheless interesting if you want to build it as component of something more complex, say DIYing a battery bank out of some recycled cells
I wonder how many changes would be required to run the whole thing on say 24 or 48V. At glance just powering the board with 12V source and just feeding more to MOSFETS seems to be enough
ElectroBoom has entered the chat ...
Seriously though, there's enough energy in those numbers to seriously mess you or your electronics up. It's not quite like a bottle of old nitroglycerin, but it's definitely enough energy/power that you must respect it.
Do you think the laborers in china understand all the words in this instruction set when they assemble electronics?
They aren't dumb. They are professionals who do this sort of thing for a living.
That said, most companies don't etch their own boards. That part of the build process could be skipped by sending your schematic out to one of the boutique board fabrication places. They aren't terribly expensive and it avoids having to deal with nasty chemicals. The article even mentions this and I would highly encourage it myself, at least until you have a few boards under your belt and are feeling more comfortable with diving deeper into the process.
No, but they are doing it on a line and with tools, parts, training etc provided by an engineer who does.
Assembly carries a different set of risks from powering something up. But as the sibling comment says, the assemblers are skilled technicians. They might lack theoretical background but they will have had a lot of apprenticeship.
The EGS002 looks like a really neat subassembly. It's just that at 1kW the safety issues are significant.
I have an old wall clock from Japan that runs on 110v/50Hz. It keeps time like all old clocks, using the frequency of power. I can plug it into a US outlet and it runs, but it runs fast, since we're 60Hz here in the US. To remedy this, I bought a 12v power supply, and an inverter from Japan that had the 50/60Hz selectable on it. I couldn't find any other inverters that had an option to run at 50Hz.
I get the feeling that the frequency wasn't checked for accuracy / stability, because the clock still eventually goes out of time. My KillAWatt shows something like 51 or 49Hz or something like that. Not good enough to run a clock.
Been looking for some other way to get 50Hz AC power... This seems like it could be promising... but I have no idea how stable the frequency will be from a project like this...
Sooooo how much power does that clock use ?
Because simplest one would be:
* a cheapo chinese subwoofer amplifier * 12V wall-wart to power it * a quartz-stabilized 50Hz generator (soooo an arduino, with DAC, even simple R2R + some filtering). * transformer fitting subwoofer amp output voltage. Measure amp output voltage at near-max, connect amplifier to secondary and tweak the "volume" till it is right.
Sub amp is like $5, $3 for cheapest arduino clone, probably like $2 for transformer, and few bucks in proto board and other components
If you want to overcomplicate it you could put rPi into it and sync the 50Hz clock to NTP
> If you want to overcomplicate it you could put rPi into it and sync the 50Hz clock to NTP
That’s ridiculous! Buy a little GPS-disciplined oscillator and either scale the PPS output up to 50Hz or use a PLL to derive 50Hz from the oscillator output :)
Just use a pll to derive 50 from 60. Problem solved.
The GPSDO will also give you correct time of day and unwavering frequency. I used to have one set up at home to feed my test equipment a 10 MHz reference.
If you're powering 50/60Hz clock you won't be setting time remotely on that easily
But how do GPSDO work? Is GPSDO susceptible to metastability?
GPS is a system for distributing time first and a means of computing position second.
A GPSDO is typically a PLL that uses the recovered timebase as a reference input and will have an incredibly slow loop filter. It can be outrageously highly damped and stable.
Such clocks are the basis of the cell network and have made doing client handoff between towers almost easy. The hard part is operating through GPS denial (mostly due to weather).
Would you mind revealing where you would go to for a power transformer that cheap? Clearly they must exist, as a full AC/DC adapter costs barely more than that, but eBay is wont to give me listings for merchandise of a certain animated TV series...
Aliexpress would be my first bet. Random used junk second
https://www.aliexpress.com/w/wholesale-12V-220v-transformer....
I've literally used an audio amplifier to directly create 240V 50Hz in a professional capacity so your idea is completely reasonable.
Yeah I have prototype (working, sans transformer) somewhere on the pile of shame.
The (presumably) low power demand means you could do pretty much anything... you could digitally control the frequency of the power to this clock if you ran your own inverter. Like in software you would know exactly how many cycles had elapsed since previous time and how many need to elapse before the next to achieve synchronization with some NTP source. There are all sorts of ways you could sort it out, assuming the clock is not mechanically slipping relative to AC cycles.
It seems quite strange that the clock isn't compatible with both 50 and 60 Hz. Japan uses both frequencies in different regions.
Fun thing is that inverter is the clock in this case. The time keeping device. The wall clock is just a display.
You could use a mechanical 60 to 50Hz converter. Basically a motor connected to a generator. They tend to be very expensive but maybe there are options.
If I were making something for this problem I would make an AC-DC-AC converter with a PLL to divide the 60Hz input frequency to 50Hz to control the inverter.
> If I were making something for this problem I would make an AC-DC-AC converter with a PLL to divide the 60Hz input frequency to 50Hz to control the inverter.
This is the best way to do it, especially if the synchronous motor inside the clock is actually fed with a lower voltage from a transformer (which seems to be common in old radio clocks as they needed a transformer anyway to power the radio circuitry). If that is the case, it should be possible to bypass the transformer entirely and build a converter that operates entirely on low voltage; some quick searching suggests that this exact kind of project has already been done before in fact [1].
> If I were making something for this problem I would make an AC-DC-AC converter with a PLL to divide the 60Hz input frequency to 50Hz to control the inverter.
I'd put a $3 breakout board with any microcontroller and quartz... why would you want to sync to power network in the first place ?
> why would you want to sync to power network in the first place
It's very stable, because it was used/ok to use for time. Well, it was until very recently [1].
[1] https://www.usatoday.com/story/money/economy/2018/05/17/cloc...
Iirc, the power grid frequency is adjusted over the long term to give excellent long term stability. A crystal will drift.
It won't keep time because on an actual mains grid the operator tracks frequency variations over time and makes corrections in the opposite direction to keep the average very close to the stated Hz - one reason for that being mechanical clock sync.
For example if the grid ran at 59.87Hz during the hottest part of the day due to high load then they might run the grid at 60.06Hz all evening offset.
You could probably hack your inverter with a simple DPLL, to keep it in sync with the wall. I'm assuming you could interface with the clock generator (cap or resistor), if you wanted to keep it "analog" :).
Or, perhaps replace the existing clock with a microcontroller that you can sync with NTP or the 60Hz line.
>I have an old wall clock from Japan that runs on 110v/50Hz.
No, it's 100V, not 110. Japanese mains power is 100VAC, 50Hz in the east and 60Hz in the west. Your clock is from the east, made for Tokyo probably. US 110-120V is a bit high for the clock, but it's close enough that it probably doesn't cause any problems.
It sounds like the inverter you bought isn't terribly accurate, unfortunately.
>Been looking for some other way to get 50Hz AC power...
Actually, it's really simple to get highly-accurate 50Hz power to power your clock. All you need to do is move to Europe. Then you can use a 1:2 step-down transformer to convert the 240V/50Hz power there to 120V/50Hz power, and your clock will be accurate.
What's the power draw of your clock? 50Hz is within the range of most LFO circuits (Low Frequency Oscillators) of the kind used for modular synthesisers and guitar effect pedals. You could combine one of those circuits with a simple voltage follower (consisting of a power op-amp or BJT transistor plus a couple of resisters) to keep the frequency at a stable 50Hz under load, and finally a transformer to convert the signal up to 110V.
All in all, I would estimate that this could be done with a single IC providing a few op-amps, a handful of passive components and a transformer; probably under US$30 or $50 with a nice case and plug.
> 50Hz is within the range of most LFO circuits (Low Frequency Oscillators) of the kind used for modular synthesisers and guitar effect pedals.
i don't think those are designed for long-term frequency stability, either. not at the <0.01% level needed for a clock. rest of your comment is on track, but the original low-voltage low-power 50Hz signal needs to come from something that was designed for low long-term drift.
Good point, and thinking about this further makes me realise just how stable the frequency of mains power is! Also, in the museum at the Greenwich Royal Observatory, I saw an exhibit of a clock which was synchronised with regular pulses in the mains electricity, which I believe were in addition to the usual 50Hz AC. However, I don't know if the power grid still has such a pulse in Britain, or whether there was/is a similar system in the USA.
I love that this discussion is rapidly headed to sticking an XO on the circuit suppling current and frequency to control the old digital clock that lacks an XO. Hackery at its finest.
Are you positive it’s not meant for 100V? That’s the standard in all of Japan from what I know.
The voltage doesn't affect the time keeping capabilities. It's based upon grid frequency. I've got one of those US<->Japan xformers I use to run a very special toaster in my kitchen. Doesn't do anything for frequency, but that doesn't matter in my particular case.
Unless you mean for sentimental value, very special personally, can we have more information on the very special toaster?
I've literally just searched 'Japanese toaster', but is it perhaps a Balmuda 'The Toaster'?
Mitsubishi Electric TO-ST1-T
Clearly, he possesses considerable expertise, but it's puzzling why such a skilled individual would falter towards the end, resulting in poor solder joints on the 2.54mm pin headers. This isn't merely a question of aesthetics; these joints are susceptible to failure.
His work is commendable, but I would encourage him to either learn proper soldering techniques or, if he already possesses the skills, to take a moment to use some flux and clean up the joints. It's a simple process that takes just three seconds per joint.
> The MOSFETs I'm using comes in a TO-220 package. The metal tab of the MOSFET is technically tied to its drain pin. Electrical isolation must be applied to avoid conduction between the other sets of MOSFETs. I usually leave the upper MOSFETs from the H-Bridge unisolated as they share a common drain pin (Vcc).
Oh holy, that's not good. If the screw threads manage to touch the inner side of the hole of the metal tab, you have electrical connection.
Besides that, I don't see a short-circuit protection on there - not sure if the "overcurrent" feedback can handle a dead short before the FETs blow up.
That's a neat little project, but as almost always nowadays, don't even expect to save any money by building an inverter yourself, unless you have the expensive parts (transformer, mosfets, driver board) lying around anyway. Otherwise, the 30$ mentioned in the article wouldn't even come close to cover all the parts in the list.
I am not an electrical engineer and stand to be corrected:
Commercial inverters for a LiFePO4, gel and lead acid batteries types usually include a micro-controller to monitor and manage the battery's state of charge. These micro-controllers usually employ a multi-stage charging algorithm to derate and prevent the battery from overcharging (which may lead to its eventual destruction).
I recently installed a cheap Chinese MUST 1000V hybrid sine-wave inverter with a relatively expensive LiFePO4 battery. Has anyone had success communicating with the RS-232 serial port to monitor this brand of inverter?
I am terribly worried that there is a bug in the implementation of the charging algorithm; the officially supported desktop monitoring app is only supported on Windows...
This seems like an irresponsible thing to make into an instructable
You can say that about a lot of things. Like anything involving an angle grinder. You can split your face with it into two if it breaks down. Best thing is testing your homebrew inverter using an angle grinder with no protection on either the grinder, or the inverter or your face.
The world would be quite boring without some fearless people like these.
Though it would have been nice to mention not to buy your mosfets from aliexpress/ebay for $0.8/10pcs (some mosfets are quite pregnant [1]). But looks like one commenter already pointed that out on instructables.
Electricity is not to be feared but rather respected. It is a powerful force that lives in our wall, pockets, cars, the air, the ground, and even something that drives our biological function.
That being said, this is not going to be someone’s first project. It probably won’t be their second project. I’m not sure my faith in people’s self preservation is rooted in my confidence that people generally want to be safe or some rather bleak, Darwinistic thinking that eventually only those who do projects recklessly will be “selected out.” In any case, you can work on these systems safely and it’s just mains voltage.
Humans have introduced more complexity to our lives as our technology has progressed, all with thought-to-be grave safety implications. The advent of the motor carriages had one city making a law stating that someone had to be on foot, waving a flag preceding the motorized vehicle at all times. People love to catastrophize, claim the sky is falling, and wax poetically about how far we have strayed from “the lord.”
You think a lot of people are gonna casually hand make a PCB?
Not correctly, which is part of the problem.
You all are right, it is unlikely that anyone will actually follow this recipe. I guess I’m taken aback that some pretty serious electrical engineering has been turned into a step by step tutorial with little mention of the potential risks.
If an inexperienced person does decide to save some money on an inverter by following these steps (as is implied), it could very quickly turn into “how to electrocute yourself and burn down your house in 10 easy steps.” I would not want to be liable for promoting or hosting such content. Similar to the issue with the “very cool” electric wood burning fad that killed a few people.
Circuit breakers or fuses on both the input and output sides would be a good idea.
The duct tape insulation at the bottom of the heat sink is a pretty bad idea, better use some mica and/or some stand-offs for this. Duct tape has some insulating properties but simply isn't made for this application and given the voltages in play I would definitely not use it.
Otherwise: this is a neat little inverter, it's basically a minor variation on the application note for the driver which does all of the heavy (PWM) lifting.
If you can't get transformers that are large enough you can put several in parallel using a small series resistance if the output voltage isn't exactly right (usually a case of one winding too many or too little on the secondary (now primary)).
Be careful too with those HV caps, those can hold charge for much longer than you might think when they are out-of-circuit. If you can use a higher voltage (48V preferred), and go for a transformerless design because that's so much nicer to haul around (besides being much cheaper).
I think the most important thing to realise is that electricity is becoming a bit like a common tool that _anyone_ should be able to wield to do amazing things.
Fire is just as dangerous as electricity, it's just that you can visibly see, feel and smell the danger before being burnt.
Electricity is silently dangerous, but education and maybe a bit more safety via simplicity would be really cool to see (e.g. light weight non-intrusive gloves that glow if near electric fields).
That’s pretty neat!
Also, I was not aware that Instructables.com was owned by Autodesk. Guess they must’ve been acquired somewhat recently.
The acquisition was a pretty long time ago but the prominent Autodesk branding at the top of the page is relatively recent.
Not exactly -- almost 12 years ago!
https://investors.autodesk.com/news-releases/news-release-de....
I think the receptacle looks so scared, because it's about to deliver 220V when it's only rated for 110V?
I'm really surprised that board is only $3 given how expensive off the shelf inverters are. I would think there would be enough competition in the pure sine inverter market to drive prices down, but I guess it's just small enough to not function optimally.
The $3 part is only the controller, though. It doesn't actually handle the power itself - it requires extra components for that. It'd be like saying a $100 microwave is expensive because it is controlled by a $0.50 controller chip.
The project page itself states that the inverter will cost at least $20 in total - and that's using essentially the cheapest components you can find. Once you use quality components and include things like proper input/output protection, connectors, and a casing, you're likely looking at a $40-50 BOM.
A $150-$200 retail price is very fair, considering all the other stuff you need to pay for to actually design, certify, make, and sell a product.
Just the tranformer costs at least $250-300 unless you get it second hand.
For this level of hobby project, there is no need to buy that new. I would either wind my own transformer or (more likely) go to the computer surplus store, get a battery-less UPS and pull the transformer from that.
> 1000W 12V –> 220V Inverter
Haha, i wonder how the radiated spectrum of this toy looks like.
After looking at the instructions, most would rather buy
I have a 2kw(?) 12v inverter that I use to power a small welder from my vehicle, it's really useful on the go for repairs.
Why doesn't the title include the efficiency?