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 12/120V inverter again
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - May 29 2008 :  6:45:11 PM  Show Profile  Reply with Quote
A TV that works properly is extremely sensitive. If it doesn't pick up a clear signal with a good antenna then the transmitter is too far away. An amplifier will just amplify its own noise.
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pebe
Nobel Prize Winner

United Kingdom
1078 Posts

Posted - May 30 2008 :  2:35:26 PM  Show Profile  Reply with Quote


quote:
I've already searched those ckts. & as a matter of fact I'm already using this ckt.(below) for a long time. The downside of this ckt is that it has less selectivity(i.e.less channel/station). http://www.elecfree.com/electronic/tv-signal-amplifier-by-bfr90-bfr91-bfw92/

Its stated output of 90uV is in error - and means nothing. But its an ultra broadband amplifier that's wide open to interference and will give a poor signal/noise ratio over any narrow band of frequencies for which it will be used.
quote:
I live in a country where typhoon visits regularly that knock-out power lines, cable system including TV aerial antenna. That's the reason why I need to boost the aerial signal for my TV.
Under those circumstances, TV reception would be the least of my worries.
quote:
I've ask this question already in another electronics forum website and they said building an aerial amp w/ such huge gain(50dB) will result for noise to be amplified also that won't benefit apprently right????
Absolutely correct.
quote:
I think I'll need to make a shorter aerial antenna*(PASSIVE) instead....but its gain will be lesser than the longer one. How about a home-made CABLE system????...Do you think its possible??????
A TV antenna is essentially a resonant half wave dipole matched to a 75ohm coaxial cable. It should feed into a matching 75 ohm load at the receiver or amplifier. I doubt the circuit you referred to will give a match anything like good enough.

Cable TV is an art in itself. It requires amplifier design and output distortion levels low enough to limit intermodulation and cross modulation to acceptable levels. It is not a practical task for a DIY enthusiast.
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ElectroEgg
Apprentece

Trinidad and Tobago
7 Posts

Posted - May 31 2008 :  12:55:06 AM  Show Profile  Reply with Quote
Helloooo. The topic here is about inverters. Is there anyone who can make adjustments to this square wave inverter circuit to produce a modified sinewave?

Download Attachment: 100w square-wave inverter.gif
15.86 KB

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pebe
Nobel Prize Winner

United Kingdom
1078 Posts

Posted - May 31 2008 :  01:20:57 AM  Show Profile  Reply with Quote
You might find help in this thread.

http://www.aaroncake.net/forum/topic.asp?TOPIC_ID=7123&whichpage=2
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ElectroEgg
Apprentece

Trinidad and Tobago
7 Posts

Posted - Jun 01 2008 :  6:44:40 PM  Show Profile  Reply with Quote
Hi Jaun. Thanks for the schematic. I would update you on my progress.
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Saso
New Member

Slovenia
3 Posts

Posted - Jun 03 2008 :  3:48:41 PM  Show Profile  Reply with Quote
I have built 500W inverter with CD4047 and 2N3055 transistors. If I connect it to my desktop power supply it works relatively OK but if I connect it to car battery it does not work there is no output, CD4047 dies and transistors and 10W resistors heat up.
When it is connected to desktop supply and it works the measurements are (for instance):
- Power supply 13V, 4A
- AC output 110 V
- DC output (after diode bridge and capacitors) 95V, 0,48A
It works fine with heavier load also. Highest reading was almost 10A input and 1A output. That is as high I can go with this power supply.
My transformer is 13,8-0-13,8/110V.
I have tried everything I could think of according to my limited knowledge of electronics.
Would you be so kind and help me to solve this problem - why it does not work with the battery.
Saso
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jun 03 2008 :  7:15:59 PM  Show Profile  Reply with Quote
Hi Saso,
You forgot to post the schematic of your 500W inverter.
Its CD4047 needs to be fed through a 100 ohm resistor then a 15V zener diode to ground to protect it from spikes.
Your power supply has an output of only 13V x 4A= 52W. A 500w inverter needs an input of 600W. A huge difference.
The voltage rating of your transformer is wrong. The RMS voltage at the output of yje inverter is probably a lot lower than an ordinary meter measures its square-wave.

Post the schematic and we will fix it for you.
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Saso
New Member

Slovenia
3 Posts

Posted - Jun 03 2008 :  7:36:39 PM  Show Profile  Reply with Quote
Thank you Audioguru. I have used the schematic that you have modified http://www.aaroncake.net/forum/uploaded/Audioguru/2007212205318_500Watts_Inverter-small.PNG
I'll add 100 ohm resistor and the zener.

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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jun 03 2008 :  10:31:58 PM  Show Profile  Reply with Quote
The 500W inverter circuit is simple and produces a square-wave. Many electronic products won't operate properly from a square-wave inverter.

The CD4047 IC also needs a bypass capacitor like this:

Download Attachment: 500W inverter smalll pic.PNG
160.81 KB

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Saso
New Member

Slovenia
3 Posts

Posted - Jun 04 2008 :  04:02:28 AM  Show Profile  Reply with Quote
Audioguru, thanks. It works.
I have one more question. If there is no load at output the voltage is 150V. If I connect the load, the voltage drops. If the load draws 0,07A the voltage is 100V and if the load draws 1A the voltage drops to 75V. Is that normal? Can I prevent that?
Saso
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jun 04 2008 :  12:01:56 PM  Show Profile  Reply with Quote
The output is a square-wave that must be measured with an oscilloscope or a "True-RMS" meter.
The battery must be a huge lead-acid one from a big car or a "deep discharge" one from a motor home.
Then when the battery is fully charged at 13.2V the square-wave output will be about 130VAC RMS without a load and about 106VAC RMS with a 500W load. The transformer should be 10V-0V-10V to 120V.
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kivdenn
Nobel Prize Winner

Uganda
535 Posts

Posted - Jun 09 2008 :  03:37:03 AM  Show Profile  Reply with Quote
Hey Juan why did you opt for this and left the one that used the CD4047 and CD4025 ICs that produced a modified sine wave output?
Thanks
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pebe
Nobel Prize Winner

United Kingdom
1078 Posts

Posted - Jun 09 2008 :  08:15:34 AM  Show Profile  Reply with Quote
Juan,

There is a mistake on your wiring diagram!

The cathodes of D3 and D4 should go to CE (pin13) NOT to ground. Wiring the way you have them will cause them, or the 4017, to pop! Your earlier circuit showed them wired correctly.
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JUAN DELA CRUZ
Mad Scientist

Philippines
476 Posts

Posted - Jun 10 2008 :  04:14:14 AM  Show Profile  Reply with Quote
To Kivdenn:

> This modified-sine inverter is
better than MSW inverter w/ CD4047 and CD4025 ICs. For the reason that this MSW inverter has a 'stable voltage output'.

To Mr. Pebe:
> Ooops! Sorry about that. I'll fix it.


HERE IS THE EDITED DIAGRAM:

D3 & D4 IS CONNECTED TO PIN 13 & R9 & C7

(CIRCUIT WHERE REMOVED DUE TO TECHNICAL REASON)

juan dela cruz
Penniless INVENTOR

Edited by - JUAN DELA CRUZ on Sep 17 2008 09:39:18 AM
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Jun 10 2008 :  11:39:28 AM  Show Profile  Reply with Quote
Now the schematic is confusing.
D3 and D4 connect to pin 5-and-a-half on the CD4017.

EDIT:
Thanks again Juan for fixing the schematic.

Edited by - audioguru on Jun 10 2008 11:24:59 PM
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