Need Inverter Ckt

Well a laptop computer would be fairly blackout resistant. Phone lines usually stay in business too.

I wonder what folks are trying to power during a blackout? Lamps? TVs? Fridge? A/C? Disco balls?
 

marshallf3

Joined Jul 26, 2010
2,358
It's late but I'll try to find a circuit for you tomorrow some time.

I assume you can find a 240V:24VCT transformer and 2N3055 or MJE3055 transistors?
A lot of others will work but they've got to be at least 60V and around 10A and 100W capable.
 

marshallf3

Joined Jul 26, 2010
2,358
This will be far more accurate (caps meay need to be adjusted for frequency) but let's see what kind of feedback we get from others on it:
http://electronics-diy.com/electronic_schematic.php?id=655

and at least they got the caps in right on this one but the parts specified are old #s: http://www.aaroncake.net/circuits/inverter.asp?showcomments=all - or did they? http://www.thefarm.org/charities/i4at/lib2/inverter.htm

I think the first one is more correct but neither are going to be very reliable over time.

In the meantime read through this: http://www.electronics-lab.com/foru...2b4526cc9525ad26b2f0fdccffc&topic=471.msg1949
 
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Audioguru

Joined Dec 20, 2007
11,248
After I complained a few hundred times that the polarity of the capacitors in the simple inverter were backwards, Aaron Cake corrected it, but that fixed only one of its many problems so it still doesn't work.
 

Tahmid

Joined Jul 2, 2008
343
Hi,
I know you want an IC-less design but this is one using ICs, I guess. I've just drawn this up and you'll get the idea quite easily.



Hope this helps.
Tahmid.
 

SgtWookie

Joined Jul 17, 2007
22,230
Why not use a 12V bulb and fan? No inverter required.
^^^^^^^ This.

Any inverter is going to have losses; even really good ones are not 100% efficient. A "hobbyist-type" inverter might be 75%-80% efficient at best.

You'll already have losses due to charging/discharging the battery. A lead-acid battery is only about 75% efficient; for every 1000mAH you put in, you only get about 750mAH back. The rest of the energy is dissipated as heat due to the chemical reaction.

Instead of trying to power 220VAC fans and inefficient incandescent lamps, try using small DC fans (salvaged from old computers if need be) and efficient LED lights or CCFL (cold-cathode fluorescent) lamps powered directly from a 12v lead-acid battery.
 

retched

Joined Dec 5, 2009
5,207
I did.

I had my basement run off of all DC.

It is VERY possible. And you can find toys and old products, like computers that sarge mentioned, to get DC motors and bulbs out of.

Look for junked cars and take the wiring and bulbs out of it.

You can even take the blower fan and motor out of the heat/ac and you will not need to make a thing.

You can make the fan blades out of old CDs or DVDs quite easily for a small personal fan.

You would be much better off forgetting AC altogether.

Wouldn't you much rather be asking:
"Can I get a circuit to change AC to DC?"
 

marshallf3

Joined Jul 26, 2010
2,358
He's got a reason so we may as well just keep going through it. Another option I thought of was to get a regular 12V:120V inverter then feed that through 120 - 240V transformer.

I'm finding it hard to improve on that circuit I posted here:
http://electronics-diy.com/electronic_schematic.php?id=655
but haven't quite figured out why there are two multivibrators in it. Takes a lot of components but at least they all seem to be fairly common.

Just how accurate do you need the output (which I'm assuming is 50 Hz) and the reliability to be? I built a couple of that really simple circuit everyone seems to complain about back when I was a lot younger but I think back then the design called for the non-polarized caps you can get from speaker building places or most any of the larger supply houses but this guy seems to have good reason for specifying tantalums.

Odd that the circuit doesn't appear so much anymore, of course when I built it it came from a book as there was no internet in those days and has been mentioned it has a ton of faults. Since you can buy a 300W inverter for next to nothing nowadays it's just faded into the limelight.

Here's a 400W one for $30: http://www.harborfreight.com/400-watt-continuous-800-watt-peak-power-inverter-66814.html or an 80W one for $17: http://www.harborfreight.com/80-watt-continuous-power-inverter-66972.html

Too bad you don't want to use an IC or two as there's a million ways to build a far better and more efficient inverter that way.

Start by rounding up a useable 24VCT to 240V transformer and see what transistors you can find then we'll take it from there.
 
I wonder if I posted on a medical forum that my friend needs brain surgery and although I have no experience or tools except an old rusty spoon an a butter knife...

I did find some 15th century sketches that used a wood drill.

Posts for UPS designs pop up at least once a month. Almost always it's because a proper UPS is beyond the reach of the OP even though they sell for next to nothing. Sending the poor fellow on a wild goose chase for pure unobtaimum isn't helping anybody.
 

Audioguru

Joined Dec 20, 2007
11,248
if u dont have related help then stop wasting my time for posting ur crap comments
Please stop your insults. Everbody on these forums say that it costs much more to make an inverter (if you can find a good circuit) than to buy one.

I don't have a good schematic of an inverter because I don't need one and cheap ones are available.
I fixed a defective 500W inverter project 5 years ago on another website but its performance is not good. It is used in a 3rd-world country by people who do not have any electricity. The inverter used old transistors that are available there. Charged batteries are delivered to them and their dead batteries are taken away to be recharged then "rented" to somebody else.

If you are so smart then why don't you post the schematic of the inverter that you use when you are in the woods?

I have never seen the schematic of a cheap pure sinewave inverter. Somebody took one apart and found a small ferrite-core transformer and two TL494 PWM ICs, one to stepup the 12VDC and the other to modulate high voltage DC with PWM. It used some Mosfets for high frequency switching.

Here is the fixed poor quality 500W square-wave inverter:
 

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OP (S2PK) would you mind telling us why you don't want to or can't just buy one. I'm guessing you're in India or Pakistan and it's priced out of reach. Curious how much are they for lets say a 500VA UPS where you live, the 1000VA ones I found for sale were 4000 Rs ($90US) which is still a bargain and still cheaper and probably more reliable than any DIY device would be. You want to avoid ICs I assume because the local markets don't carry any, they're also not likely to carry any of the other parts you'll need.

As I mentioned before, why not use 12V Lamps & Fans?

Also worth mentioning an Inverter is only half of a UPS, you still need a charger.
 

debe

Joined Sep 21, 2010
1,389
This circuit is about as simple as it gets for a 300W inverter & its only a square wave, but it still uses 2 Ics to drive it. Idid build this about 4yrs ago, but since replaced it with a comercial one as they are sooo cheap, in fact cheeper than this one to build.
 

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marshallf3

Joined Jul 26, 2010
2,358
Shoot, a 400W one showed up for $20 with free shipping:
http://www.newegg.com/Product/Produ...22810-Index-_-CarAccessories-_-82021068-L018D

If I could even think of the most remote need I'd have for one I'd order it, then again I may do so anyway for that price just to have it around to take on the occasional camping trip.

[EDIT:] Why not? The reviews aren't bad at all and at 400W continuous for $20 with free shipping I can even make a half decent UPS out of it given a spare battery. I'm guessing it's going to draw somewhere in the neighborhood of 36A at full output considering it's modified sine wave so if I take it camping I'll just pick up an extra 12V car battery from the salvage yard and take it fully charged. We've got a self service one here that pulls all the batteries out of the cars they get in and if they test good they sell them for $10 regardless of age, I've picked up a couple for friends that, by the date codes, were only a few months old before whoever had the car retired it for one reason or the other - probably because the new battery didn't fix the problem. Kind of a no-brainer even if it only lasts for half of the one year warranty period so I just pushed the button and will probably have it Friday.
 
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