Speaking of inverters

[drdongle]

I remember that in the past several people had anounced that they were working on home brew inverters and had posted some prelimainary pictures and schematics. What is the status on these?

[nothing to lose]

I remember those also and wondering the same.

Also wondering if anyone is trying to re-invent the inverter by salvaging and moding old UPS's.

I bought some NON-working Ups's cheap when I picked up my Matrix. $5 each, several are over 1000watt sinewave. I just got 1 working tonight and it's now worth more than I paid for all of them

Only real problem was the bateries were totally shot in this one, cases busted on both, may have froze in Ohio in the mini van perhaps if they were totally dead. But it did nothing when bought either.

 This inverter would not even turn on or self test when plugged into the wall, now it even cold starts direct from the batteries.

Seems to me all the parts are there in a sinewave Ups cheap for those trying to build one. Just rework it the way you need it.

[terry5732]

There are plenty of inverter plans out there - use google. You don't need a pure sine wave for most things and the simple ones will be fine as long as you have adequate component ratings. Once you have the plans, check cross reference tables for substitute (scavenged ) parts. An old favorite of mine is   http://www.aaroncake.net/circuits/inverter.htm

[thunderhead]

I was one of them.  Other tasks kept being put in higher priorities, often by my wife.  My current prorities are

2. My kitcar died, and needs a new engine, so I want to put an electric one in it;
   
1. My wife insists we sell the house next month and buy a smallholding in Ireland, and that means lots of DiY jobs to get it finished.
   
   

When we get the smallholding, we're not even planning to be on the grid, so we'll build the microwave oven transformer invertor then.  I have a feeling that when we get there, a windmill and an invertor may be set as highest priority.

But I don't set the priorities, she does!

[drdongle]

Good luck with that, I hope you like oil lamps!

[drdongle]

Yea I've seen that one before in several versions, it's a "classic" circuit. Those projects I was speaking of were to be a bit more advanced.

[Experimental]

   Hi thunderhead and Dr D !

    I really have to agree with Dr D, about likeing oil lamps, espically if you intend to be "off grid", and even more so, if you intend to keep your woman happy!!

   I have a little cabin, off grid and I can tell you -- there is nothing more important than good batteries and an extremely reliable inverter !!

I have repaired a few, and burned up several and at this point, have invested (heavily) in a heavy duty inverter !!

   You can, of course, operate on 12 or 24 volt lighting and RV type appliances, but there are times, those things just aren,t enough and life insists on a few conviences !!

   Home made inverters would be fine for hobby type things, but as yet, I haven,t seen anything, that I would want to depend on -- that also includes the cheeper, factory made variety !!

   For a happy homelife, I really advise -- don,t skimp on an inverter !!!

 Happy building all, Bill H.......

[Nando]

High power inverters are difficult builds by "experimenters" so most of the ones that can offer one are reluctant to do it for that reason.

Basic reason I do not offer schematics -- First the effort to offer it is EXPENSIVE in time, if you are willing to offer it , it would take many hours ( sometimes several hundred hours ) to make the circuit work reliable.

Just to offer the schematic and CAVEAT EMPTOR for the one trying to build one, is not my doing.

I have many designs that have been done under company money, so those can not be given away, though so many ask me to GIVE them away -- They are not MINE -- period.

To spend the time to develop a KIT that anyone can build takes a lot of time and money that unless many buy it, it would a financial disaster, so a job in futility.

MANY -- means several thousands !!

Now you know the reason why the products from a company like from OUTBACK cost so much, it may take 2000 hours to design a product like the MX60, to work reliably and long term -- do you care to calculate what this development cost is ?.

Many ask me to up load schematics for certain circuits that require a lot of work to build -- and now you have the reason for me not to do it --

Many months ago there was somebody designing a sine wave high power inverter -- that from the beginning had troubles and I started to show him where the problems were -- he may have thought that I was trying to copy ( steal ) such design - so he did not responded to my messages -- still the design has not appeared yet -- HOPEFULLY it will appear one of these days.

The simple high power inverter MSW type, is one using high voltage battery bank from a beginning ( 120 volts) that can be made with most available --FINISHED -- parts with a limited manual work in the output section -- 1 to 10 KW is possible -- but how many members of these groups, if they have a 120/240 volts battery bank, are going to spend the money for such effort ?.

I receive constant requests for complicated circuits, that I do not accept to do, even with CAVEAT EMPTOR -- because it may comeback later with requests to fix what one or a few built and is not working.

Only way, would be if a group of people with enough knowledge in electronics get together and in a group build the prototype and develop the KIT, I have done in Radio and Radio frequency years ago.

Early satellite receivers.

No such group exist for such endeavor.

Nando

[Bruce S]

NANDO;

   I hear ya.

I have read many inputs from you and find them thoughtful, the fact you take the time to go into detail in explanations, to be one of the greater assets of this forum.

I like many don't have either the time nor the money to research this , and the Xantrex's are there, ready to be bought, installed and counted on.

Cheers!

Bruce S

PS> I too would never give away something belonging to this company, I like paying my bills on time and really have no desire to meet bubba .

[oztules]

Hi Nando

As I see it so far, you can overcomplicate things to be negative, or you can find another way which may be more likely to have success. It may not be necessary to have a high voltage batt pack in order to make a low cost higher power inverter for dummies.

It may well be that a welding transformer, a low power inverter, some igbts and driver trannies as per the fanmans setup, would just as easily be doable. If you use the inverter as the signal driver for the fets or igbt's h bridge via the four small 12v transformers on a 48 volt batt pack, and used a welding transformer to step up the voltage to "line" then you will achieve a closer to sine wave output from a simple "fairly bulletproof" setup, which would probably do what most people require

The igbt's at 200Amp and the batt pack at 48v gives a fair output. Some of may wish to rewire the transformer to ct and use only two igbt's and two 12v transformers.

Questions:

1. why is this not possible. If they can wire up a stator, then they should be able to hook these components together. Not even a curcuit board is necessary.
   
2. Why would this simplified system not work
   
3. would the transformers inductance and hysterisis change the chopped up square wave into a more sinusoidal shape under load.
   
4. I haven't done this kind of thing yet. Ihave designed and built pwm devices. Those at battery potential have been ok (up to 2kw traction motor control), those involving 240v ac line projects were much less forgiving, and required much more testing and more blown fets. Yes i finally got it to be very forgiving, but took time.(24v batt chargers pwm but full current at 0-45v also modifying computer supplies for 0-29v 15A  yes providing full current at short circuit allowing start of low impedance loads (dc motors))
   
   

It would take less time to scribble a wiring diagram onto a piece of paper scan and post it, than some of your more lengthy postings would have taken, but would help some of us to move forward with these things.

 When I finally get time to work on this end of things, I will post the wiring diagram, of what worked for me... not just talk about it. You have this in your head already, and know what will work and what will not.

If the dans and hugh were like this, this forum would not be here, we'd all be buying air403's

So Nando, I urge you to at least get the simple circuit you have described on screen like jerry has done, and give some of us an option that we may take at our own volition...

Nando:.."The simple high power inverter MSW type, is one using high voltage battery bank from a beginning ( 120 volts) that can be made with most available --FINISHED -- parts with a limited manual work in the output section -- 1 to 10 KW is possible -- but how many members of these groups, if they have a 120/240 volts battery bank, are going to spend the money for such effort ?.".

post it and we will find out . If the transformer is workable on msw then probably more than you think.

.........oztules

[dinges]

Nando, I agree with you, partly. It's not an easy thing to design. Can't give away what isn't yours. Takes a lot of work to design such stuff.

Then again, what the Dans are doing took a lot of design work too. Trial and error. Start calculating their development costs...

Yet they choose to make all that information available. For which I'm very grateful.

It are two completely different philosophies on the dissemination of information.

I know the one I prefer. And out of gratitude, I even try to make my experience and knowledge available here, every now and then.

And I would never build a real high-power inverter. It wouldn't even be economical, I think. But I would like to have a peek at such schematics (and not the '2x 2N3055s and a transfomer' type inverters... Yawn) and decide for myself. Not even a caveat emptor. Simply CAVEAT!

Peter.

[terry5732]

Kudos - well said - I wouldn't have been as kind

It isn't rocket science - which itself is overrated

Almost nothing needs a perfect or even close to perfect sine wave

Your transformers will greatly elongate the square wave input

Figuring out the Gate, Source, Drain on a MOSFET is far easier than figuring optimal coil magnet arrangement in a genny

ALL the components can easily be scrounged for FREE from the mountains of discarded consumer electronics

You can learn more electronics by browsing online than from a mumbling college professor

You could even use a multitude of wall wart transformers in parallel - provided they are all the same - rather than a single large one

Why would you even post that you know this and that and then say you WON'T tell?

Sorta sounds like "I found a cold fusion process but own oil stock"

[Nando]

Dinges:

The DANS do prototype by trial and error one by one, the same way that others may need to do with a product that has a lot of "relaxed dimensioning", because the unit is quite forgiven.

Through trial and error they have developed a group of ideas to implement in a broad range with trial and error setting of the RPM cut in or furling point.

How many can do electronic trial and error design and build a good well behave long term product ?.

To compare a mechanical design with a complicated electronic design in equal terms the precision of the mechanical parts is not going to be +/- 0.001 inches but 0.000001 inches of precision -- so how many would have the equipment to be accurate to 1 microinch ?.

In the electronic circuit the precision may be needed to be 20 to 100 Nanoseconds = 0.000,000,02 to 0.000,000,1 seconds.

Just a simple comparison that many may fight -- it is just a relationship for you to think about.

Some DIE HARDs may go for "microwave transformer" idea Inverter, well, how many ?.

The only thing I have read is the idea and no circuits have been presented or shown.

Just some reasoning for the lack of available complicated circuits for any to construct.

Nando

[Nando]

I expected exactly that from you, you are one of those that DO WANT THE CIRCUIT NO MATTER WHAT.

It is better to give a commentary about certain circuit and see what happens in interest for it.

The transformerless idea, I presented to see what kind of interest may appear and until today, no one really interested to build one.

I designed such transformerless inverter about 8 or 10 years ago and only 3 has been built, I gave the design away, that even showed ways to produce 10+ KW for 115 volts and 30 KW for 220 volts -- because very few people think in the advantages of high battery voltage --

Fanman found something close to it and he bought the schematic -- with free time I will try to draw improvements for his ckt -- consulting time is my priority -- it pay well, that one day of work pays more than one week of work for many.

What do I prefer to do ?. I suffer of insomnia and when that happens I may seat down at the computer and scan this group and others, as well as, the assistance I give to several groups in undeveloped countries that need help in technical areas in several other disciplines besides those here.

Nando

[oztules]

I'm sorry Nando. I didn't think that you were endeavering to put bread on the table. that puts a different light on your posts. I'm sorry to have interferred with your livlehood.

You will hear no more from me.

Once again please accept my apologies for interfering .

..........oztules

[oztules]

Yes terry5732

I feel a bit of an arsewipe for not knowing that he was proffering his help for a fee, (which I'm not sure this forum is designed for, but I don't know that it isn't either). And yes I felt that it had a "teaser" feel about it, but as I said, didn't realise that his income relied on such things. I'm not here to stop the guy making a living. It would have helped to clear things up sooner if he had stated clearly what his motives were. However, we now know.

Some people will appreciate the service he offers, and he will no doubt be filling a need that is real....just not my needs.

I have no doubt that I will build whatever I please as well or badly as I want. I am a lazy slob who would not mind someone else doing the hard work first, instead of re-inventing the wheel, but hey, gives us all something to do.

I will no longer attempt to interact with him as I don't need his services, but others may. So Good luck to Nando, I guess the rest of us will muddle along.

........oztules

[thunderhead]

I don't like oil lamps: I have an inquisitive two-year-old.

But I don't need them, in spite of having power cuts every few months here in the outskirts of London.  You see, many years ago I built a UPS for a friend's webserver project, and with the 800kg of batteries I bought a couple of years ago, it provides plenty enough to run our boiler, our fridge/freezer, and as many CFLs as you could ever want.

For days.  Days, and days, and days.

You should see my wife's smug face when our house is the only one in the street with light and heat.  Her husband is a qualified, capable electronic engineer, not some hobbyist.  At times like that, she knows it.

But that's just a little invertor, big enough for lighting and a few services.  It won't run the microwave oven, or a washing machine, or an immersion heater.  It certainly won't run a power shower or an electric cooker -- or recharge an electric car, for that matter.

The reason I haven't tried to knock up a 12kW invertor in a weekend is because I know perfectly well that it's a bigger project than that.  When I have the time to devote to it, I'll share with you all, almost certainly under GPL.

The design I have in mind is a few of the little ones, all working together, and switched in and out as needed, for efficiency.  Getting them to work together might be tricky, but it's control electronics, not power electronics.

In the meantime, let's not have the "you can't do it, I'm the only one with any education" conversation again, please.  It's all in the archives, if you really want to read it.  And, in the meantime, there's no point in this sort of willy waving -- if I do it, you'll know who is right, and in the meantime, you don't.

[wdyasq]

While reading this post I typed a few words into a search engine.  ODD, because by he time I finished reading the post I had a found something:

http://www.energychallenge.org/2001Reports/TAMU.pdf

Of course it is an old design - 2001 and the parts are expensive - $500. In a quick scan I think a prototype has been run and tested.

Ron

[thunderhead]

In the electronic circuit the precision may be needed to be 20 to 100 Nanoseconds = 0.000,000,02 to 0.000,000,1 seconds.

Just a simple comparison that many may fight -- it is just a relationship for you to think about.

When typing this reply, I expect to position my fingers to within 0.00001 of a mile, and get the timing right to within 0.00000001 of a year.  Amazing I can achieve such accuracy by hand!

The point is that my keyboard is not a mile across, and it doesn't take a year to compose a reply; so the measurement is not about precision at all: it is merely about scale.

[Nando]

Yes, TAMU design has been in Internet for long time.

If one wants to build that one, it would cost not U$500 but around 2 to 3000 dollars ( single price parts) plus 200+ hours of work -- then GOOD LUCK with the software to run the microprocessor -- it is not available --.

I was aware of it, early when released, just to be familiar with the software, I tried to get the source code -- no luck, even tough I had, in TAMU, a professor friend trying to get it for me -- the students kept it and the professors did not care to keep copies.

The students are gone and most of them will be using the design for their own benefit-- financially --.

It is a good design, I mean, excellent design.

This design with a U$500 material costs, it may end up with a sale price of around 2500 to 3600 dollars -- for a manufacturer being able to make around 20 % profit if 1000 units are sold yearly.

The prototype was for a smaller power output if I remember right.

Nando

[Nando]

AMAZING:

Go ahead and build a wind mill one mile in diameter with 0.00001 of a mile precision -- then tell me how well it works .

Nando

[thunderhead]

What would I do with a mile high windmill?

[craig110]

"What would I do with a mile high windmill?"

Call it a nice prototype and start working on a two mile high windmill.  :-)

[Experimental]

    WOW, sure didn,t mean to spark a fire here Thunderhead -- and I would be the last person, to ever say "you can,t do it" !!

All I really ment is -- when a family is moveing off grid,and you mentioned,"next month" -- I assumed, time was of the essence !!

   When you are suddenly , Off grid Perminently, power takes on a whole new meaning and many of us, have spent many hours, days and months, building and repairing inverters -- or trying to !!

   You may well be the guy to do it, and if you come up  with a reliable and powerfull inverter, that can be built for less than the factory made items, please share that with the rest of us -- I,ll be one of the first to build your design, as I sure would like to have a standby, for the $1,000 one I have right now !!

   I appologize for irritating you, and wish you lots of luck and hope to see that design on this forum  -- happy building, Bill H.....

[johnlm]

I can sympathize with Nando's position to some degree.  I spent 27 years working at Hewlett Packard in the Oscilloscope / Logic Analizer division and can attest to the difference between high precision highly reliable products and the time it takes to design them and develope the manufacturing process to build them verses the faster do it simple and cheap approach to getting a unit or two working that requires reasonably constant maintainence to keep it working because a worst case design is not done.  There is a time and place for both approaches and the approach that is used by most on this board is the faster and simpler approach.

I have been playing around the last week or so with an example of a fast and simple approach to a DC Amp hour meter (parts cost maybe $10 to 15 if bought new, much less if parts scrounged) that I believe will work fine for me (and likely many others) but I have been deliberating whether or not to put it on the board once Im done just because Im not sure I have the time or patience to answer all the questions that will come.  I suspect most of the folks that have commented on this posting have the knowledge and where-with-all to quickly and easily replicate the design from the schematic and go on about their business, and likely even improve it; but when I see the number of questions I do with people struggling with understanding the basics of Ohms law or whatever, I can forsee a significant amount of time trying to help many folks getting one to work or where to get parts or whatever.  Maybe that is why some folks publish schematics with the statement of no support or guarantees.  In this arena there are always folks that will try to build something they have very little understanding about and then ask alot of questions which I have seen as frustrating at times to some of the more knowledgeable folks.  And one answer and approach is that everyone has to start somewhere and support is given to assist folks to learn.  On the other end of the spectrum there are times that I read a post and really fear that some poor fellow is going to kill himself playing around in an area he problably should not.  Luckily most of this RE electrical stuff (invertors not included here) is low enough voltage to be pretty safe, but I suspect if homwbrew invertor schematics were posted commonly on this site there would be alot more risk for the poor fellow who doesn't know that magnet wire is not magnitized wire and for the peace of mind for the fellow that supplied the schematic worrying if this guy is going to kill himself.  I wonder if there is a web site out there used by doctors and non-medical people with the doctors trying to help the laymen perform surgury?

I don't mean to step on any toes here.  I really admire the patience and professionalism that many on this board exhibit helping others.

Just my thoughts.  

Johnlm

[thunderhead]

It's OK: I'm more irritated at others, both here and elsewhere.  If you dip into the archives, you'll see the problem here: and if you imagine me carting in 800kg of batteries because my wife interrupted someone trying to steal stuff for scrap from our back yard yesterday, you can maybe understand.

Next month is when we aim to put this place on the market.  I'd love for us to move into our new smallholding next month, but I suspect the vagaries of the property market are a bit slower than that.

Which is a shame: I want to be constructing real stuff, not fiddling with display electronics for mobile phones; and my wife wants to be planting, not plastering. :-(

[oztules]

Johnlm

 " I can sympathize with Nando's position to some degree." so could I until he admitted to openly skulking around trying to obtain a copy of someone elses work to further his own ends by the use of his surruptitious professor friend.

I can't countenance that.

As for wheather or not the folks out there are capable of deciding to build or not to build... its for them to decide.

Having done a fair amount of power electronics on my own by necessity, I have learned a lot about what doesn't work. BUT it is easy to build copies of other pwm units, wind your own transformers, and play with switchmode if you have an original to follow.

I found that it's when you decide you know better, and start differing from a set path that things go astray. If you follow a succesfull design, I found no problems provided the current regulation feedback system was tested on lowvoltage, before the mains was applied. If this simple calibration is done, then it self protects fairly well.

When I made my own design, I learn't about back emf fairly quickly, and spectacularly. I found the the guys on the testla sites had the best simple power designs. H bridge, balls an all multikilowatts and simple construction. I fail to see why they can see that others can follow, when the Nando's of the world feel they are the only ones.......but for a few dollars all that changes......... so the arguments are hollow or sanctamonious or both.

For me, it is disappointing that this sort of mindset has a place here, the Dans have done so much to give not just take. So has Hugh Piggott. He's there for a few dollars, but he has given the world far far more than he has taken. His site describes exactly how to build a windmill, but we all buy the book anyway. I found his book over in this country s/hand, but instead bought it new from the Dans, and paid international postage as well, because THEY went the extra yard, and deserved something for that .I have no doubt that the Dans do better with this site than without it, but I never hear them push for dollars for information. Quite the opposite. Their free disemination of knowledge draws people to them and our respect.

The Nando's of the world will struggle to get respect when it is clear that he will do whatever it takes to procure information so that he may derive a profit at a later date. It's not even that he attempted it, it's that he feels that it was a fair thing..no not for mine.

So no , I can no longer sympathise with his position.

[TomW]

oztules;

Just one thing to say:



My sentiments, exactly the world has enough takers and we need more givers!

Cheers.

TomW

[thunderhead]

I spent 27 years working at Hewlett Packard in the Oscilloscope / Logic Analizer division and can attest to the difference between high precision highly reliable products and the time it takes to design them and develope the manufacturing process to build them verses the faster do it simple and cheap approach to getting a unit or two working that requires reasonably constant maintainence to keep it working because a worst case design is not done.  There is a time and place for both approaches and the approach that is used by most on this board is the faster and simpler approach.

I don't see these two as the only options.  It is perfectly possible to design circuits based on worst case design and maybe some additional windage, and end up with something that a home constructor can put together and get a reliable result.

In production, the issue is not "worst case design", it's "can I save ten cents on this component, and so reduce the cost of making 1,000,000 units by $100,000?"

But if a circuit is intended for home construction, maybe with the components only reaching 30% of their rated maximums, and no component value being critical, then 100 home constructors can assemble them and, provided they put the components in the right way around and do a decent job of soldering, 100 of them will get a working result.

If the components end up costing an additional $5 because of the conservative design, most home constructors will not worry too much.  It's still $500 cheaper than the one they might have bought.

This sort of design technique used to be very popular, particularly for things like amateur radio and home entertainment systems.  It's rather fallen out of fashion outside the amateur radio hobby, but fashion doesn't really affect engineering as much as non-engineers think it does.

[finnsawyer]

I'm not sure what you are getting on about here.  It is relatively easy to break time up into small consistent bites.  In the early seventies I invented a simple crystal oscillator circuit that was capable of one part in 10^7 precision at room temperature.  That is, no attempt was made to maintain a constant crystal temperature.  The University (read that as non technical bureaucrats) that I worked for at the time declined to seek a patent.  I believe to this day that they threw away millions of dollars in royalties, when one considers the tremendous demand for crystal oscillator circuits in watches and computers of the day.  I feel that a comparison between mechanical and electronic precision is really meaningless.  Each has its natural precision, which comes out of the basic physics underlying it.  A precision of one part in 10^7 or greater in electronics exists only because it is possible by the underlying properties of electronic devices, such as the quartz crystal.  

[Nando]

We are in the same boat, in the early seventies, I, as well, developed a stable crystal oscillator set with 10^-7 precision at room temperature range (0 to 60 degrees Celsius), one single network correcting 11 crystals for the Mobile telephone service (IMTS) that was the predecessor of the Cellular phone.

I did get a patent for the invention, though the company went bankrupt by the bad management of the CEO, Of course I lost a great amount of money, which could have made if the company have gone public or sold, which the CEO, unhappily, refused to do when a excellent offer came in.

We had well known film and TV artist investors.

Nand

[nothing to lose]

Put it on a mile high tower and end the worlds electric problems.

Half of dia, half mile, 1 mile tower would have the bottom of the rotor 1/2mile high and top of rotor 1 1/2 mile high. What is the jetstream mph at those heights?

Hmm, come to think of it, what is the wind speed at 1/2mile and 1 1/2 miles, perhaps there is such a thing as too big? What happens to a gennie if the top half of rotor gets 60mph winds and the lower half only gets 20mph winds?

[nothing to lose]

" I wonder if there is a web site out there used by doctors and non-medical people with the doctors trying to help the laymen perform surgury?"

I would like to go ahead and get rid of the apendix before it gives me serious problems at a inconvienant time, but don't want to pay the money since the work is not needed right now. Hmm, such a site would be good, I could save few bucks and the daughter (age 14) could maybe get some practical experience