About: I am a photographer, a tinker, an electronics technology engineer, and author; I write short stories and poetry for the love of writing. I started writing poetry in high school over thirty years ago where I ...

When I lived on the farm; beyond normal household appliances I had a wood burning stove for cooking and heating, a PTO powered generator for when there was no wind, and a windmill for hydro and water when there was wind, but not much in solar power. Most of the time I lived on the grid, but when the power was out for weeks during the ice storm that hit Ontario and Quebec or the blackout that hit the whole east coast, other than a couple added chores my life did not change we even had a windmill in the field to water the cattle.

Step 1: FOOD

I grow crops and raised livestock as well as I am a good hunter, gatherer, and fisherman, I can get my meals from the wilderness when I need too.


I live in town now the bylaws don’t allow me to install a windmill or a wood burning stove so I have a propane barbeque with extra tanks for cooking when the hydro is out. $200.oo


I have a Coalman 3750 portable generator and two jerry cans of gas to run the refrigerator and freezer in the summer and the furnace in the winter. In the winter I can put the refrigerator and freezer outside in the cold. I could not build one for the $175.oo this one cost me. For the generator fuel, additive will make the gas last a year in storage.


I have flashlights that don’t need batteries the little one you pump to charge up, the larger one you shake to charge up. 12 of them at $2.oo each I can’t build them that cheaply.


This 400 watt power inverter is strong enough to run my satellite and TV, it cost me $25.oo easier and cheaper to buy than to build. A friend of mine got a 1000 watt inverter for $10.oo.


Other than the solar array I built the other 12 volt 2 watt cost me $20.oo for the pair. I use these to charge batteries.


Other than solar arrays I build power packs, this portable power pack I built from components I retrieved from the garbage it consists of a 12 volt 10 watt hour deep charge battery and a 200 watt inverter all of which I got from the garbage. This power pack combined with my laptop can keep me connected to the internet all evening while it charges and runs off my solar cells during the day.


Due to a lightning strike I lost a lot of work that was not on the net, the lightning strike fried my computer and the backup connected to it. So I have been redoing a lot of my work now I regularly copy my work on CD disks.

I was inspired to design this modified sine wave generator by thirteen, two thousand watt, industrial power inverter circuit boards; I bought for ten dollars. I took one circuit board apart to reverse engineer how it worked, and it did not have a signal generator. They are four-bank push pull mosfet driven inverters, beyond the difficulty of building a four bank sine wave driver I know the optocouplers on the circuit board cannot handle a sign wave driver, so I designed a modified sine wave signal generator.

Pure sine wave inverters are best, however they are expensive to buy or build. Modified sine wave inverters will power some equipment square wave inverters will not, and cost about the same as square wave inverters to build or buy.

This final circuit just needs a couple tweaks on the battery monitor and fan control circuits.

I should be able to build a 120 240 volt 22,000 watt power supply to power my home with circuits left over.


I am already building a circuit board for the modified sine wave signal so I don’t want to modify the Inverter boards. Finding connecting leads has been a pain. These I salvaged from old computers.


There is a lot you need to know to completely design an inverter this is just the basics to help you build your own.

Unless you can acquire a custom made transformer your circuit design is ruled by the transformer available to you, if the primary winding is not center taped you are limited to an AB driver. The only transformer you can play with is a center tap primary, if the primary winding is center taped then you can use an A, B, C, and AB inverter driver and it can be supplied with 12 or 24 volts and 6 or 12 volts you can’t play with the watts.

If the primary winding is 1000 watts run max then your inverter is limited to 1000 watts run max and about 1500 watts startup surges.

The transistors and mosfets should be watts doubled, take an IRF640 it is 200 volts 16 amps and 136 watts. That is 200 volts at 0.68 amps to 8.5 volts at 16 amps not 200 volts at 16 amps. An IRF640 will get hot at 12 volts 11 amps constant running doubling the transistors and mosfets will keep them from overheating at full wattage use.

Optoisolators protect the signal circuit from feedback and power surges; they send the signal from the signal generator by light in one direction to the transistor bank.

These three 50 Hz inverter circuit designs are easy to build and the signal circuit is accurate to 1%.

This circuit can be broken down to seven components.

1. Power Supply
2. Voltage Regulator
3. Timer
4. Signal Converter
5. Optoisolation
6. Inverter Transistor Bank
7. Transformer
There can be more components when you add charging and low battery circuits.

These circuits are 24 volts center grounded and AB type inverter; 12 volts center taped primary winding B type inverter, and 12 volt AB type inverter.

Voltage regulator components
3-1N4002 diodes
1-220uF 16v
1-1uF 16v
1-1uF 6v
1-1 k&

Timer Components
1-12 k&
Use 1-24 k& for 60 CY or 1-30 k& for 50 CY or 1-39 k& for 40 CY
1-0.1 uF
1-10 nF
Any multivibrator with a 240 Hz output for 60 cycles, 200 Hz for 50 cycle, and 160 Hz for 40 cycles will due for the timer circuit. The duty cycle is not important as the first JK flip flop converts the signal to 50% duty cycle and ½ the hurts’.

Signal Converter Components
2 to 4-1.5 k&

From the And gate output resistors to the rest of the Inverter circuit the value of the active components depends on the power supply and the inverter transformer.


If you have a digital analyser the internal signals should look like this, however if you don’t have a digital analyser slowing down the frequency and using LEDs can enable you to see the signals.

I hope this will help others build Inverters.



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    23 Discussions


    3 years ago

    Great info, thanks! Where do you get all of your stuff so cheaply? Where did you get that little flashlight, I've never seen one like that! Thanks!

    1 reply
    Josehf Murchisonblakehx

    Reply 3 years ago

    I got the little flash light at the Dollar Store and they are great you pump the handle and the LEDs light up.

    The 400 watt power inverter and the 2000 watt power inverter circuit boards I got at a liquidation store.

    The little inverter in the clear plastic I salvaged from a Black&Decker booster tossed out to the waist bin.

    I have 4 900 watt APUs and 3 1500 watt APUs all from the waist bin that just needed batteries.

    You would not believe the good stuff people throw out that only need the smallest repair, $200 and $600 UPS for the cost of a $50 battery.


    4 years ago on Introduction

    was hoping that you might have any info on old-school wind (turbine) powered water pump for a well... trying to be off the grid but our well is deep.. having a hard time to wrap my head around the issue, may be that *archimedes screw* could do it, however all illustrations have it at an angle?


    5 years ago on Introduction

    You mention the generator to power your furnace. We just went through the worst storm in 125 years here in Toronto so I'm looking for a long term solution like this. First, how would you hook the furnace up? A long extension? Then, does it control the thermostat by itself? Next, is it possible to hook up the deep cycle batteries to the generator meaning you only have to run it now and then. I'm thinking fridge/freezer and furnace, that's it. Thanks!

    1 reply

    First DO NOT RUN THE GENERATOR IN AN ATTACHED GRAGE OR THE HOUSE. A fellow in Barry was running his in the attached grage and the gasses killed him and his elderly mother this week.

    I live in Shelburne Ontario about an hour and a half N/W of you, there are still people without power near me.

    Not all thermostats work the same but mine runs directly off the furnace so when I power the furnace I power the thermostat.

    I disconnect the furnace from the mains and plug it into the generator with a long extension.

    A little trick here during the summer I bought a pool toy, foam noodles I use as a weather seal to keep the patio door sealed from the cold.

    My generator is 3500 watts and the furnace only uses 800 to 1000 watts so I can run all three at the same time, however I like my TV, satellite, and Internet. Its colder here in Shelburne than Toronto and I put the fridge outside when it is cold so I can use the extra wattage for other things. That won't always work in Toronto for more reasons than one.

    You can use deep cycle batteries and a pure sine wave inverter for intermittently running appliances. The induction motors in appliances don't like square or modified sine wave inverters so pure sine wave is best for them. And then keep them charged up with the generator.

    I hope this is helpful and Happy Holidays.



    6 years ago on Introduction

    This is a life to live by. To be self-sufficient is to be strong enough to take care of yourself and your family. Only then can you help others. Thank you Sir for inspiring me and other to do what we think is right. You brother in the trench with you, Matthew Lalowski.

    1 reply

    This month we have had an ice storm and a tornado knocking out the hydro for a day twice.

    The ice storm knocked the hydro out at 5:30 am; I started up my Coleman 3750 generator at 6:30 and warmed up my propane barbeque to make breakfast.

    My neighbor is a single mother of 3, I invited her and the kids over for breakfast and they watched cartoons with my sons while they ate a hot breakfast, everyone else in the neighborhood sat in the dark or went to the warming center in town.

    All the stores in town were closed because their tills need hydro so the whole town was closed but the warming center me and two other people with generators. I had all the enmities of modern day living even the internet to track the storm.

    Way to go! Your projects are wayears and years beyond my capacity of understanding, but your comment about putting the fridge outside in winter really intrigued me. Can you tell me more details. ie. what about sleet, and snow on top of it. doesn't that kill it?

    3 replies

    Dear Josef, I live in asia, and would love to help you out with your daily work, and hopefully learn some electrical stuff, Will work for free, as long i got food, a place to stay and some knowledge on electronics to be gained

    1 reply

    6 years ago on Introduction

    Josehf - Great Instructable! I am curious in your final step showing the various wave forms with the output being a stepped sinewave if for example a 100uh @ 40 amps choke were placed on the output side of the transformer. Would this be enough inductance to round off the corners of the steps to be more like a natural sinewave?

    1 reply

    I don’t know how much a 100 uH 40 amp choke would round the wave form, I was building the signal circuit for the existing circuit in step 8 and since the circuit wasn’t made with an inductor other than the output transformer so I didn’t try it.

    The last step is more about the signal generation and sharing it, people have a hard time making pure sine wave inverter circuits. Modified sine wave inverters run things square wave inverters wont, the wave forms show you if you are building the signal generator right.

    You can add caps to the output of the transistor/mosfet banks, but they would be very large 200 volts 4800 uF and up depending on current draw. The Inverter circuit in step 8 of this instructable has 8 caps, 4, 200v 4800 uF and 4, 2.2 uF, the only thing larger on the circuit board is the 4 ¼ inch long heat sinks for the mosfets, everything else on the circuit board is tiny in comparison. At 20 amps run 30 amps surge I am not sure how a 40 amp 100 uH choke would act on the output.

    The only downfall of a pure sine wave inverter is a lower surge tolerance. For readers that don’t know what surge is, a motor runs on 5 amps while running but draws 10 amps when it starts. Most of us have seen the lights dim when the fridge starts. Modified and square wave inverters have a high tolerance to serge’s up to 60% as to 20% in pure sine wave inverters.


    6 years ago on Introduction

    sweet im going to do what u did when i get older but my projects are going to beconnect to a camper

    1 reply

    If you buy the components to build a system, don't pay more than $5.oo a watt, less is better on solar panels and $0.10 a watt for a Modifide sine wave inverter or $0.15 a watt for a pure sine wave inverter.

    My Coalman generator cost me $0.05 a watt the solar cells cost me $2.50 a watt and the 400 watt power inverter cost me $0.06 a watt.