12V to 120V Inverter

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Have you ever wanted to run a TV, stereo or other appliance while on the road or camping? Well, this inverter should solve that problem. It takes 12 VDC and steps it up to 120 VAC. The wattage depends on which tansistors you use for Q1 and Q2, as well as how "big" a transformer you use for T1. The inverter can be constructed to supply anywhere from 1 to 1000 (1 KW) watts.

Important: If you have any questions or problems with the circuit, see the forum topic linked to in the Notes section. It will answer all your questions and provide links to many other (and better) inverter circuits.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
C1, C2	2	68 uf, 25 V Tantalum Capacitor
R1, R2	2	10 Ohm, 5 Watt Resistor
R3, R4	2	180 Ohm, 1 Watt Resistor
D1, D2	2	HEP 154 Silicon Diode
Q1, Q2	2	2N3055 NPN Transistor (see "Notes")
T1	1	24V, Center Tapped Transformer (see "Notes")
MISC	1	Wire, Case, Receptical (For Output)

Notes

Q1 and Q2, as well as T1, determine how much wattage the inverter can supply. With Q1,Q2=2N3055 and T1= 15 A, the inverter can supply about 300 watts. Larger transformers and more powerful transistors can be substituted for T1, Q1 and Q2 for more power.

The easiest and least expensive way to get a large T1 is to re-wind an old microwave transformer. These transformers are rated at about 1KW and are perfect. Go to a local TV repair shop and dig through the dumpster until you get the largest microwave you can find. The bigger the microwave the bigger transformer. Remove the transformer, being careful not to touch the large high voltage capacitor that might still be charged. If you want, you can test the transformer, but they are usually still good. Now, remove the old 2000 V secondary, being careful not to damage the primary. Leave the primary in tact. Now, wind on 12 turns of wire, twist a loop (center tap), and wind on 12 more turns. The guage of the wire will depend on how much current you plan to have the transformer supply. Enamel covered magnet wire works great for this. Now secure the windings with tape. Thats all there is to it. Remember to use high current transistors for Q1 and Q2. The 2N3055's in the parts list can only handle 15 amps each.

Remember, when operating at high wattages, this circuit draws huge amounts of current. Don't let your battery go dead :-).

Since this project produces 120 VAC, you must include a fuse and build the project in a case.

You must use tantalum capacitors for C1 and C2. Regular electrolytics will overheat and explode. And yes, 68uF is the correct value. There are no substitutions.

This circuit can be tricky to get going. Differences in transformers, transistors, parts substitutions or anything else not on this page may cause it to not function.

If you want to make 220/240 VAC instead of 120 VAC, you need a transformer with a 220/240 primary (used as the secondary in this circuit as the transformer is backwards) instead of the 120V unit specified here. The rest of the circuit stays the same. But it takes twice the current at 12V to produce 240V as it does 120V.

Check out this forum topic to answer many of the most commonly asked questions about this circuit: 12 - 120V Inverter Again. It covers the most common problems encountered and has some helpful suggestions.

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Comments

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anonymous 12VDC To 120VAC Inverter Tuesday, February 02, 2010 10:52:23 AM

this circuit is a short cut, suitable for driving amplifier, and a light load like mobile chargers, cfl's, etc. for a party or picnic. i would not advise anyone to extract more than 1KVA at the most because this circuit is basically an astable multivibrator and has no: 1. frequency check, 2. overload protection, 3. battery cut, 4. battery charger and will have a rather very poor performance!! cheers.

Rupali V Remje 12VDC To 120VAC Inverter Tuesday, February 02, 2010 9:30:37 AM

Sir, I am not finding the transformer since the data of the the transformer are not enough to purchase. So please can you specify more information about the transformer so that it will be easier to me to purchase the transformer.

GRAIN 12VDC To 120VAC Inverter Wednesday, January 20, 2010 1:17:12 PM

HEY I AM WANDERING IF THE TRANSISTER ARE TO ANGLE ONLY 15A AT 12V POWER SOURCE

OTH 12VDC To 120VAC Inverter Saturday, January 09, 2010 1:58:34 AM

This is a "classic" circuit that has floated all over the Internet. It is amazing that no one has made corrections. If you build it "as is", while it will show an "AC" voltage at the output of your transformer, there are numerous problems. First of all, the shown connection between the center tap and the rest of the circuit should be opened and the CT connected only to the 12 volt + lead. This will reduce idle current from about 2 amps to less than a half amp. It will also allow the proper voltage to appear at the transformer output instead of a reduced voltage (as one reader reported above). Next, all resistors should be increased in wattage ratings to at least 10 watts, preferably 20, for cooler operation. Finally, the timing capacitors should be increased in value to around 100 uF and should be BiPolar. The simplest way to acheive this is to use 2, 220 uF electrolytics in series connected at their minus ends with plus ends connected at the circuit points. One other improvement would be to add choke/cap filters to the "AC" output or, at least, a small value (.05 or so) high voltage cap across the output to reduce transient spikes and harmonics.

anonymous 12VDC To 120VAC Inverter Saturday, December 19, 2009 2:09:45 PM

Ok, so I saw that the Q1 and Q2 and T1 (the transistors and Transformer) are what determine the # of watts, but would I need to make the other components such as the diodes, capacitors, etc. be larger as well or can they be any size as long as the Transformer and Transistors are good enough to handle the wattage? Pls. email me if you have an answer. Big thanks to anyone who responds.

Mark 12VDC To 120VAC Inverter Tuesday, December 15, 2009 12:31:14 AM

Using this schematic what size components would i need for 30kW? If unknown, what formulae would be used to detirmine each required component specs based on known input/output voltages?

EDC 12VDC To 120VAC Inverter Friday, November 20, 2009 3:39:03 PM

had anybody maked a 1.5kW inverter already with thiss Schematic? and if it is what kind of transistor we need and transformer capacity if necessary? thank you for your reply EDC.
(Editor's notes: Won't work.)

blackcorvo 12VDC To 120VAC Inverter Wednesday, November 18, 2009 4:53:51 PM

Hello there! I have a little question: I need just 10w of power, because i wanna build a small tube amp and i can't find power transformer for less than 200$. so i wanna build a small power inverter for recticifying the 230v AC to get the B+ I need. What changes i should make in the circuit? is there any other circuits i could try? thanks for any info!

anonymous 12VDC To 120VAC Inverter Wednesday, November 11, 2009 12:11:48 PM

Hi, I really like this website, and it has helped me in many projects i did. I faced some problems while making this circuit and some compnents has over heated. But i made some corrections and it worked. :) To see the corrections i did please click on this link. http://www.lz500.com/upfiles/Tjr59306.jpg thanks

anonymous 12VDC To 120VAC Inverter Monday, November 09, 2009 6:47:15 AM

I have 4 nos 12v 9ah sealed battery. How can I use them all to make a 220v invertor. The circuit should also charge the batter when mains are on

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anonymous	12VDC To 120VAC Inverter	Tuesday, February 02, 2010 10:52:23 AM
this circuit is a short cut, suitable for driving amplifier, and a light load like mobile chargers, cfl's, etc. for a party or picnic. i would not advise anyone to extract more than 1KVA at the most because this circuit is basically an astable multivibrator and has no: 1. frequency check, 2. overload protection, 3. battery cut, 4. battery charger and will have a rather very poor performance!! cheers.
Rupali V Remje	12VDC To 120VAC Inverter	Tuesday, February 02, 2010 9:30:37 AM
Sir, I am not finding the transformer since the data of the the transformer are not enough to purchase. So please can you specify more information about the transformer so that it will be easier to me to purchase the transformer.
GRAIN	12VDC To 120VAC Inverter	Wednesday, January 20, 2010 1:17:12 PM
HEY I AM WANDERING IF THE TRANSISTER ARE TO ANGLE ONLY 15A AT 12V POWER SOURCE
OTH	12VDC To 120VAC Inverter	Saturday, January 09, 2010 1:58:34 AM
This is a "classic" circuit that has floated all over the Internet. It is amazing that no one has made corrections. If you build it "as is", while it will show an "AC" voltage at the output of your transformer, there are numerous problems. First of all, the shown connection between the center tap and the rest of the circuit should be opened and the CT connected only to the 12 volt + lead. This will reduce idle current from about 2 amps to less than a half amp. It will also allow the proper voltage to appear at the transformer output instead of a reduced voltage (as one reader reported above). Next, all resistors should be increased in wattage ratings to at least 10 watts, preferably 20, for cooler operation. Finally, the timing capacitors should be increased in value to around 100 uF and should be BiPolar. The simplest way to acheive this is to use 2, 220 uF electrolytics in series connected at their minus ends with plus ends connected at the circuit points. One other improvement would be to add choke/cap filters to the "AC" output or, at least, a small value (.05 or so) high voltage cap across the output to reduce transient spikes and harmonics.
anonymous	12VDC To 120VAC Inverter	Saturday, December 19, 2009 2:09:45 PM
Ok, so I saw that the Q1 and Q2 and T1 (the transistors and Transformer) are what determine the # of watts, but would I need to make the other components such as the diodes, capacitors, etc. be larger as well or can they be any size as long as the Transformer and Transistors are good enough to handle the wattage? Pls. email me if you have an answer. Big thanks to anyone who responds.
Mark	12VDC To 120VAC Inverter	Tuesday, December 15, 2009 12:31:14 AM
Using this schematic what size components would i need for 30kW? If unknown, what formulae would be used to detirmine each required component specs based on known input/output voltages?
EDC	12VDC To 120VAC Inverter	Friday, November 20, 2009 3:39:03 PM
had anybody maked a 1.5kW inverter already with thiss Schematic? and if it is what kind of transistor we need and transformer capacity if necessary? thank you for your reply EDC. (Editor's notes: Won't work.)
blackcorvo	12VDC To 120VAC Inverter	Wednesday, November 18, 2009 4:53:51 PM
Hello there! I have a little question: I need just 10w of power, because i wanna build a small tube amp and i can't find power transformer for less than 200$. so i wanna build a small power inverter for recticifying the 230v AC to get the B+ I need. What changes i should make in the circuit? is there any other circuits i could try? thanks for any info!
anonymous	12VDC To 120VAC Inverter	Wednesday, November 11, 2009 12:11:48 PM
Hi, I really like this website, and it has helped me in many projects i did. I faced some problems while making this circuit and some compnents has over heated. But i made some corrections and it worked. :) To see the corrections i did please click on this link. http://www.lz500.com/upfiles/Tjr59306.jpg thanks
anonymous	12VDC To 120VAC Inverter	Monday, November 09, 2009 6:47:15 AM
I have 4 nos 12v 9ah sealed battery. How can I use them all to make a 220v invertor. The circuit should also charge the batter when mains are on