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 12/120V inverter again
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audioguru
Nobel Prize Winner

Canada
4214 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
4214 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
4214 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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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Apr 11 2007 :  3:03:38 PM  Show Profile  Reply with Quote
2 hours per day is not long enough to charge a big car battery.
Half of a 556 is a 555. Make a 50Hz oscillator with one half of the 556. Then connect pin 2 to pin 6 together as an input(on a 555, look to see which pins on a 556) then it is an inverter.
A CD4027 is completely different to a CD4047.
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sid_ric
New Member

Uganda
3 Posts

Posted - Apr 13 2007 :  04:50:58 AM  Show Profile  Reply with Quote
Thanx alot for the advice, I have come up with a schematic, I have calculated it to oscillate at about 55hz
please have a look and correct me if anything is amiss.
http://www.geocities.com/sid_ric/556-oscillator-inverter.gif
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kivdenn
Nobel Prize Winner

Uganda
535 Posts

Posted - Apr 13 2007 :  09:44:50 AM  Show Profile  Reply with Quote
Hi guys I would like to try some other FET power inverter circuit because Gary\s circuit kind of delays to turn on for the first 1/4 second.COuld we solve this or opt for other circuits
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Apr 13 2007 :  11:49:52 AM  Show Profile  Reply with Quote
Hi Sid,
Your 556 doesn't make a square-wave. It makes an assymetrical rectangular wave.
I modified it so its output charges and discharges the capacitor through the timing resistors equally.

I didn't check the frequency but maybe the pot I added will adjust to the correct frequency.

Hi Kivden,
You forgot to provide a link to Gary's inverter. I don't have time to search for it.


Download Attachment: 556 push-pull oscillator.PNG
35.72 KB

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Binary 1011001101
Nobel Prize Winner

United Kingdom
569 Posts

Posted - Apr 13 2007 :  5:58:09 PM  Show Profile  Reply with Quote
Ive been trying to make this inverter on this page posted by audiougru, http://aaroncake.net/forum/topic.asp?TOPIC_ID=2996&whichpage=24 uses the CD4047 a/bisable mutivibrator IC, I also cannot find this so I used a 555 fed into a fip-flop driving transistors, The output is a low voltage of 18VAC, the input is 12.8V at 2 amps, transformer used was a 240v to 12-0-12. If I use the 0-12 windings it outputs a voltage so high it makes my multimeter spark and frazle inside!
Anyone know why? Also I have not used the op-amps and the small transistors to drive the 2N3055.

Thanks.
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Apr 13 2007 :  9:37:07 PM  Show Profile  Reply with Quote
Binary,
Yor oscillator/flip-flops have an input of 12.8VDC and the output is 18VAC? How?

If you feed 18VAC into the 12V winding of a 240V transformer then its output will be 18/12 x 240= 360VAC.

Please upload your schematic.
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Binary 1011001101
Nobel Prize Winner

United Kingdom
569 Posts

Posted - Apr 14 2007 :  03:12:13 AM  Show Profile  Reply with Quote
I don't know why, its really weird.
Here is the schematitc http://i96.photobucket.com/albums/l178/binary10101/inverter.jpg
Ok screw what I said in my previous post, It gives out the HV when using the schematic above, I can even draw small sparks...

Edited by - Binary 1011001101 on Apr 14 2007 09:24:38 AM
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Apr 14 2007 :  10:25:04 AM  Show Profile  Reply with Quote
Binary,
You saved your schematic as a fuzzy JPG file type instead of a very clear GIF or PNG file type. Why???
Then you uploaded it to PhotoBucket instead of here. Why???

I calculate the frequency of your 555 oscillator at 68Hz then the flip-flop divides it down to only 34Hz which is way too low. A capacitor marked "104" is 0.1uF.

The minimum input voltage for a 7812 regulator is 14.5V but you have only 12.8V. So it won't regulate and its output voltage is about only 10V.

You don't show which flip-flop IC you are using. It must be Cmos because TTL would fry with a 12V supply. The output current of Cmos with a 12V supply is only about 15mA which is way too low to drive 2N3055 transistors for power.

Your transformer is way too small for an inverter. Its max power is only 12V x 200mA= 2.4W. The output voltage would be very freaky without a load.
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