While you are on the subject. I copied the inverter schmatic from the free site. The 2 PNP transistors listed don't exist. does anyone know what Radio Shack 276-2025 cross over to? and what watts do the resistors need to be?

 

sounds like the famous 2-transistor inverter schematic, known to be a good producer of smoke and blown components...
http://www.electro-tech-online.com/v...inverter+smoke

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EEgeek.net

 

Ray, what free site are you talking about? We can't read your mind. How about posting a link to the schematic?

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Ron

 

This 500W square-wave inverter has been reported to work well:

Attached Images

500watts_inverter-small.png (156.9 KB, 940 views)

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Uncle $crooge

 

Even that is not a great inverter design. Nowadays an inverter uses low loss MOSFET transistors to switch transformers at high freq to generate a 220v rail (or a pair of +/- 220v rail) through filter caps and switch between them at 50Hz/60Hz.

I thought about building an inverter once but no longer see it as a good project. If you can, just buy an inverter. They're quite cheap and effective, much safer too.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

Yeah, I just fixed that fairly simple inverter project that was full of shorts and wrong values on its original schematic, and added enough cheap 2N3055 transistors to keep the few original ones from melting.
It was 1st made in the Phillipines where Mosfets couldn't be found.

Remember milk delivery and empties pickup in North America and Europe? In the Philippines they have charged battery delivery and pickup of discharged ones to allow their many inverters to keep their TVs and fluorescent lights working.

Yeah, the cheap Chinese inverters are tiny, lightweight, have a built-in fan and a display of battery voltage, power output and other stuff. :lol:

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Uncle $crooge

 

except for purely resistive loads , is there any other use for the sq: wave inv: ?

 

Most cheap inverters have a square-wave output.
In the Philippines they are used to power TVs and fluorescent lights that certainly aren't a resistive load.
Also they are used to power power-tools with motors that are inductive, not resistive.
The only thing that might be in trouble with a square-wave inverter is something electronic with a power transformer that charges its main filter cap to the peak voltage of a sine-wave mains. In a square-wave inverter, the average voltage and the peak voltage are the same, and the peak voltage is much less than the peak voltage of a sine-wave.

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Uncle $crooge

 

Im sorry to bump this but Ive been thinking..

The main purpose of an inverter is to invert 12v into 120V Right? So you can run 120V things from 12V....well Lets for say you wanted to run a microwave off of a car...Why go spend the money on an inverter when you can just remove the Diodes and Regulators from a Alternator? Theorectically you will have 120V (but at some frequency...I dont know what freq a alternator runs at..)

 

I didn't know that a car's alternator can supply 1kW. If you remove its diodes and regulator then your car won't go very far. You might as well remove the diodes and regulator from the microwave oven also, because its power transformer certainly won't work at the high frequencies of the alternator. :wink:

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Uncle $crooge

 

Well I was using the microwave as an example..lol

I know they can supply around 65Amps or so..which would be..7800W...

(Im using 65 as a theortical number since batterys can hold that much...)

In which...the only use it would have is powering lamps in case of a power outage....heh power your house with your car!

EDIT: well you can always hook up a gas engine from a lawn mower, and use some weird gear ratio to get 60Hz.

Unless it already runs at 60Hz in a car.

 

65A at 14V isn't 120V is it? It might be 120V at a high RPM and without a load.

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Uncle $crooge

 

I think we have a misunderstanding here. If we were to remove the diodes and regulator from an alternator, you would have pure unregulated AC Voltage. Theoretically it should be 120V.

 

Ain't no theory that says that. First off an alt generally makes 3-phase as far as I understand which a regular transformed cannot take, at best you could tap 1 phase. The reg could in theory be hacked so that it adjusts the field to make a 120v output but I'm not sure how much current it would make like this. And you have to remove the connection between the alt and battery and be running the vehicle with no alt charging it, which can kill the battery pretty fast.

The alt output is several times the engine RPM, which may cause trouble with many devices.

In short, just get an inverter. They're not expensive anymore.

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

 

Sorry, but you're talking rubbish!.

You could rewind an alternator to provide a higher voltage, as it is they are wound for low voltage and high current.

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