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 12/120V inverter again
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cyclopsitis
Nobel Prize Winner

Canada
732 Posts

Posted - Mar 07 2007 :  5:51:07 PM  Show Profile  Click to see cyclopsitis's MSN Messenger address  Reply with Quote
Not to mention that it takes a lot of engineers (elite, "smarter" then the normal person) a lot of thinking, prototyping, and research to get a circuit that is near 80% efficient! This is not something that the average electronics guru (not implying our audioguru on this site haha) can just put on paper and come up with it.

Why is this inverter thing so popular anyway? Even on other forum sites people always ask about inverters, wanting to build one!? WHY?

People, save your time and money. If you want a 1000W+ inverter buy one! Tripp-Lite makes really good ones for $300US.

K
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Mar 07 2007 :  7:03:29 PM  Show Profile  Reply with Quote
It is easy to make a fairly efficient square-wave inverter. The ouput transistors switch on and off so they hardly get a chance to get warm.

We are in Canada where electricity is nearly everywhere, is cheap and hardly ever fails. Some countries with billions of people don't have any electricity so they use inverters and car batteries to make their own.

In The Phillipines there are guys who pickup your dead battery and exchange it for a charged one, then they take the discharged one back to the big city for recharging.

In India there are rolling blackouts because they can't make enough electricity for everyone.
In Africa I don't know what they do.
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cyclopsitis
Nobel Prize Winner

Canada
732 Posts

Posted - Mar 09 2007 :  6:19:12 PM  Show Profile  Click to see cyclopsitis's MSN Messenger address  Reply with Quote
Oh that makes sense, I'm a typical westerner (take things for granted).

Thanks for the info guru :D

K
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junkfunkydude
New Member

3 Posts

Posted - Mar 22 2007 :  9:48:07 PM  Show Profile  Send junkfunkydude an AOL message  Click to see junkfunkydude's MSN Messenger address  Reply with Quote
Hi, this might have been mentioned earlier, but I'm too lazy to look it up.

I am attempting to use this inverter circuit to make a 120vdc to 12vdc converter. I was planning on inverting the 120vdc ,and converting it to 12vac by means of a transformer. This could then be rectified.

I ran into some trouble finding tantalum caps rated at 120V, any suggestions?

BTW, I don't care what frequency the inverter runs at. It could be 10hz or 10khz for all I care.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Mar 23 2007 :  12:04:48 AM  Show Profile  Reply with Quote
This inverter circuit doesn't work.
Besides, its parts are rated for 12V, not 120V.
Where are you going to find 120VDC?
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junkfunkydude
New Member

3 Posts

Posted - Mar 23 2007 :  4:36:39 PM  Show Profile  Send junkfunkydude an AOL message  Click to see junkfunkydude's MSN Messenger address  Reply with Quote
quote:
Originally posted by audioguru

Besides, its parts are rated for 12V, not 120V.
Where are you going to find 120VDC?



First of all, I know they are rated for 12v, not 120v, this is why I am searching for higher voltage rated components. I have been successful in locating replacements for all the components accept for the capacitors.

Second of all, if you really want to know the application for a 120VDC inverter circuit, here it is:

I recently purchased a 900MFD 125V electrolytic capacitor for the bargain price of $2.50 US. I did the math and found out that 900MFD at 120V is a capacity ruffly equal to 3aHr at 12V. This means that large capacitors at high voltages have higher capacity to weight ratio than any battery including Li-Ion cells. This astonishing capacity to weight ratio is only attainable at high voltages, so in order to make a virtual battery pack from a capacitor, voltage must be converted from the low voltage that would be used to charge the pack to high voltages before it goes into the capacitor, stored at high voltage, and then get converted back to a manageable voltage for use. If I can get this system to work with my 120V cap, I will attempt to build a virtual battery around a 400V capacitor.

This project is still on the drawing board, so if anyone has a suggestion on how to build an inverter based voltage converter, or any suggestions about how to do this efficiently without using inverters and a transformer, please let me know either in the forum, by e-mail, or by IM.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Mar 23 2007 :  6:53:29 PM  Show Profile  Reply with Quote
A capacitor is not a battery. Its voltage begins to drop immediately when current is drawn and drops very quickly. 900uF at 125V is not a high capacity. Super capacitors are measured in FARADS. 10,000 times more capacity.

Charge your capacitor to 120VDC. Then it can supply 120mA for only 1 second. Then its voltage will be only 44V.
Invert the 120VDC down to 12V then it can supply 100mA for only 10 seconds when its voltage will drop to 4.4V.
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junkfunkydude
New Member

3 Posts

Posted - Mar 24 2007 :  10:09:01 AM  Show Profile  Send junkfunkydude an AOL message  Click to see junkfunkydude's MSN Messenger address  Reply with Quote
You apparently misread the unit of measure of my capacitor, I is 900MF, not 900uf. This makes a huge difference. Also, this specif is project is just to "test the waters" if all works well, I'm thinking about getting a 2F 400v cap and doing the same thing.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Mar 24 2007 :  11:55:34 AM  Show Profile  Reply with Quote
There is no such thing as a 900MF capacitor with a value of 900 million Farads.
Maybe it is "only" 900mF which is 900,000 uF.
Then it will supply 120mA for 1000 seconds which is 16.7 minutes and its voltage will drop from 120V to 44V.

Four AA size Ni-MH rechargable cells will provide the average power of 10W longer and their voltage won't drop as much.
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cyclopsitis
Nobel Prize Winner

Canada
732 Posts

Posted - Apr 05 2007 :  10:37:06 PM  Show Profile  Click to see cyclopsitis's MSN Messenger address  Reply with Quote
Sometimes higher end caps like Mallory or ones made in the UK will say on them MFD I'm looking at one right now :D. Its the same as uF as far as I know just a differnet way of printing it.

K
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Apr 05 2007 :  11:21:00 PM  Show Profile  Reply with Quote
Capacitor manufacturers should learn the proper suffixes for their products:
1) M= million.
2) m= milli which is thousandths.
3) u= micro which is millionths.
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pebe
Nobel Prize Winner

United Kingdom
1078 Posts

Posted - Apr 06 2007 :  09:02:30 AM  Show Profile  Reply with Quote
As far back as I can remember, capacitor manufacturers in the UK like Plessey and Daly used MFD as an abbreviation for microfarad. Even a 100nF cap was refered to as 0.1MFD.

No doubt if they had still been in business they would have changed to the current convention, but unfortunately there are just about no UK owned electronics manufacturer left in the UK.
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sid_ric
New Member

Uganda
3 Posts

Posted - Apr 09 2007 :  10:51:01 AM  Show Profile  Reply with Quote
Hi

I live in africa and I am trying to build an inverter to make my nights bearable. I started with the schematic at
http://www.electronics-lab.com/projects/power/033/index.html but mid way through the project i found out from this thread that it is defective so I now building the one modified by the great audioguru (http://www.aaroncake.net/forum/uploaded/Audioguru/2007212205318_500Watts_Inverter-small.PNG.)

I have most of the components but the questions I have are

1- can I use ic LM324 in place of LM358 because the former are now lying idle on my bench and Iam finding it difficult to spend more.
2- CD4047 is hard to find here but i have a NE556 monostable multivibrator, is it possible to use this instead of the 4047. I would appreciate it if someone provided a schematic of how I could connect it to the setup

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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Apr 09 2007 :  11:21:04 AM  Show Profile  Reply with Quote
quote:
Originally posted by sid_ric
I live in africa and I am trying to build an inverter to make my nights bearable.

No electricity in the jungle? How will you charge the big car battery that powers the inverter?

quote:
1- can I use ic LM324 in place of LM358 because the former are now lying idle on my bench and Iam finding it difficult to spend more.

An LM358 has the same opamps as in an LM324. An LM358 has two opamps and an LM324 has four opamps. Just change the pins numbers and disable the unused opamps.

[/quote]2- CD4047 is hard to find here but i have a NE556 monostable multivibrator, is it possible to use this instead of the 4047. I would appreciate it if someone provided a schematic of how I could connect it to the setup[/quote]
The CD4047 is perfect for making a square-wave inverter. It has a stable oscillator and a frequency divider that gives each side exactly the same time period. It has one output inverted from the other.

You can use many other oscillators in this simple inverter. A 556 could use one half as an oscillator and the other half as an inverter. The 556 doesn't need the dual opamp, use series 330 ohms output resistors to feed the transistors.

Edited by - audioguru on Apr 09 2007 11:23:25 AM
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sid_ric
New Member

Uganda
3 Posts

Posted - Apr 11 2007 :  12:11:46 PM  Show Profile  Reply with Quote
Hi
Thanx for the reply audio, we have electricity for a couple of hours during the day so I could use that time to charge.

Iam not an electronics guru and I don't really get what you mean by

"A 556 could use one half as an oscillator and the other half as an inverter. The 556 doesn't need the dual opamp, use series 330 ohms output resistors to feed the transistors."

I can atleast make the 556 as an oscillator but have no idea about the inverting part.

I was looking through some old equipment and I came across a part labeled HCF4027BE. I looked at its specs on the web and found out that it is a Dual JK flip-flop, is it possible to use this instead of CD4047
I would appreciate your response.
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