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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Sep 27 2006 :  7:46:14 PM  Show Profile  Reply with Quote
quote:
Originally posted by Benito
Is there a formula or table that can be used to guide the tinkerer to switch the parts neccessary to get more power out in proportion to the small power in?


An electronic circuit cannot make power!

Power out must be less than power in because of losses that cause heating.
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Benito
Apprentece

5 Posts

Posted - Sep 28 2006 :  1:45:40 PM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru
An electronic circuit cannot make power!

Power out must be less than power in because of losses that cause heating.


I understand that power must come from some where before the circuit, as designed, can alter that power.

Why asked for a table or formula?
1. I am an amateur in electronics and definitely want to learn.
2. I would like to become skilled at calculating how many amps will come out of the circuit along with the 110V at 60 Hz when the source of the power is a 12V battery. Would also like to figure out which parts to replace in order for the circuit to handle 2 or more 12V batteries in series for more power or parallel for higher input voltage.
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Sep 28 2006 :  8:32:08 PM  Show Profile  Reply with Quote
quote:
Originally posted by Benito
I would like to become skilled at calculating how many amps will come out of the circuit along with the 110V at 60 Hz when the source of the power is a 12V battery.

Power= Volts x Amps. 12V (battery)x 500A (rediculously high current)= 6000 Watts into the inverter. The inverter circuit isn't perfect so heats with 1000 Watts. Therefore the total output power is 5000 Watts which is 120V at 41.67A.

quote:
Would also like to figure out which parts to replace in order for the circuit to handle 2 or more 12V batteries in series for more power or parallel for higher input voltage.

In series the batteries double the voltage, in parallel they double the current. The inverter circuit and its load determine the amount of output power if the batteries can supply it.

The text in this project is wrong. It doesn't give more power just by using more powerful transistors or transformer. This project doesn't work anyway.

A properly designed inverter has a max output power. Increasing its output power is a complete re-design.
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Benito
Apprentece

5 Posts

Posted - Sep 29 2006 :  06:19:41 AM  Show Profile  Reply with Quote
quote:
Power= Volts x Amps. 12V (battery)x 500A (rediculously high current)= 6000 Watts into the inverter. The inverter circuit isn't perfect so heats with 1000 Watts. Therefore the total output power is 5000 Watts which is 120V at 41.67A.


Nice! The voltage was increased by a factor of 10, and the amps reduced by a factor of approximately 12. Therefore, 12V x 60A = 720W. The output is then 120V x 5A = 600W. Got it!
quote:
In series the batteries double the voltage, in parallel they double the current. The inverter circuit and its load determine the amount of output power if the batteries can supply it.


Batteries in series, the voltage is added. In parallel, the amp is added. Got it!
quote:
The text in this project is wrong. It doesn't give more power just by using more powerful transistors or transformer. This project doesn't work anyway.


Only the simplicity of the schematic attracted me to the forum and increased my desire to learn how it works, and then put one together. I took a look at the 500W schematic you provided a link for and it does not look simple or easy to build by some one like me. So, at the moment I need help with the calculation on how much to put in, what is going to happen to that, what is the role of each component, what comes out, etc.

1. Now, what does the amp rating of the transformer do to the current? (I presumed it is something basic, right?)
2. Is this correct? Two 12V 60A batteries in parallel = 12V x 120A = 1,440W. The output is then 120V x 10A = 1,200W

Thank you, audioguru, and please patiently continue helping. I am looking forward to be a great apprentice to/with all of you mentors.

Edited by - Benito on Sep 29 2006 08:54:43 AM
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Sep 29 2006 :  09:25:12 AM  Show Profile  Reply with Quote
The 500W inverter that I helped fix uses many cheap power transistors that are available in The Philippines where it is used a lot. The transistors could be replaced by fewer power Mosfets in a slightly different design if they are available.
A transformer for a 500W inverter needs a 50A low voltage winding (600W from 12V battery, 100W wasted as heat = 500w output)so it would probably need to be custom-made.
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tim
Mad Scientist

198 Posts

Posted - Oct 02 2006 :  9:24:02 PM  Show Profile  Reply with Quote
HEY GUYS, ANYONE OUT THERE HAVE ANY USEFUL CIRCUITS FOR THE CAMERA FLASH CIRCUIT. ALREADY MADE A FAST STROBE. THERES GOT TO BE SOME USE FOR A CIRCUIT THAT MAKES 325 VOLTS.
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sbresani
New Member

3 Posts

Posted - Oct 05 2006 :  09:36:15 AM  Show Profile  Reply with Quote
hey, im doing a project for school and doing the dc/ac inverter, but is there a way that instead of getting an output of 120v i can get 24v?
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tim
Mad Scientist

198 Posts

Posted - Oct 08 2006 :  12:11:48 PM  Show Profile  Reply with Quote
well to make an inverter but to put out 24v ac , maybe you can try a throwaway camera flash circuit and take away the diode then becomes ac but use resistors to bring down the voltage.
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Benito
Apprentece

5 Posts

Posted - Oct 09 2006 :  1:15:37 PM  Show Profile  Reply with Quote
Audioguru, did you get to see the schematic Maloy was descibing?
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Oct 09 2006 :  1:54:25 PM  Show Profile  Reply with Quote
quote:
Originally posted by Benito

Audioguru, did you get to see the schematic Maloy was descibing?


Who is Maloy?
Which schematic of what?
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Benito
Apprentece

5 Posts

Posted - Oct 12 2006 :  05:35:17 AM  Show Profile  Reply with Quote
quote:
Originally posted by maloy

Hi guys, today I'll try to explain how to do it working.First of all : I am not an electronic engineer but a mechanic so I vill explain everything from mechanical point of view. At the beginning , when I started to build inverter I tried to follow instractions and finished with exploded capacitors . After several attempts and losing my money again and again I started to think that there something wrong. Thus surcuit itself is not bad or wrong , what was wrong? From technical point of view the transistors are not synchronized and practically we have some sort of backwave that mean that circuit conduct current back through capacitors to transistors, so simply there is no longer direct current but some sort of alternative current ,thus my solution is cheapest bipolar capacitors, in my case:47uf 50v electrolite caps,they work great never getting hot. Next point : do not use expensive power transistors , they are good but if you get them overloaded the next thing they could be used for is to be thrown away thus they are not so durable. What can I say about their cheap brothers (2sd850 , 2n3055) you can overload them for a short time without problems bbut do not forget about appropriate colling . the schematic is not so powerful as stated but said that could be designed for greater output . In the state the schematic presented it can produce no more than 35-40w at 120v and not capable to initiate transformers ratios designed for 240v, the usage of more powerful transistors can solve that problem but they simply getting overloaded, why? because physical thickness of conductor is not thick enough; we drain huge amounts of current through curcuit and if you remember that to rotae dc motor rated at 1hp at full load we need condactor wire no less than 3mm in diameter , so what the thickness of the transistors legs? Solution is use as many as you can instale , connect them in paralel (I use 4 of 2n 3055 2on each side) so they act as one big super transistor and their combained thickness is powerfull enough to connect any load you like. Transistors mast be connected to each other with reasonably thick wire . The rest of curcuit could be connected ordinary as you like, my transformer is was taken from video recorder power supply,its dimensions;5x5x6cm. This transformer has been rewind , I used wire from microwave transformer for centertaped winding I used thick wire and for output winding the thin wire.So if you did not anderstand something just ask me and I'll try to enplane everything, other way the system should work without any major adjustment.


I am referring to this Maloy...
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audioguru
Nobel Prize Winner

Canada
4214 Posts

Posted - Oct 12 2006 :  6:33:04 PM  Show Profile  Reply with Quote
Benito,
This inverter circuit doesn't work. Its capacitors are backwards and the transistors' emitter-base junctions have avalanche breakdown like a zener diode, causing extremely high current to be wasted in the capacitors and transistors. The base current for the transistors is too low and more powerful transistors or a more powerful transformer won't make any difference.

I linked to a 500W inverter that uses 8 2N3055 output transistors, 2 2N3055 driver transistors, 2 medium power pre-driver transistors, a dual opamp and a Cmos oscillator and it works well. The link is gone now and I can't attach it from my hard drive to here.
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tim
Mad Scientist

198 Posts

Posted - Oct 17 2006 :  6:13:28 PM  Show Profile  Reply with Quote
ok, forget it guys i spent almost 2 years trying to get that very inverter circuit to work. well i did how many caps later and how many transistors but never the way i thought it would work. rewinding transformers the works so i finally put it to rest and if you guys dont do the same you might need a head shrink. all i was ever able to get that inverter to power was a 19 inch color tv for a minute and a half .
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shivick21
Apprentice

Philippines
57 Posts

Posted - Oct 24 2006 :  03:38:54 AM  Show Profile  Send shivick21 a Yahoo! Message  Reply with Quote
is it posible to use our old PSU transformer that uses switching tech on this Inverter? well PSU converts sine wave to square wave before it fed itself to the transformer... instead of 60 hz of 220/110 volts... it regulates its cycles on the demand of watts that needed for the pc.. if you seen china's schematic or their inverter products. the have the max rating of 600-800 watts w/ minimal power loss coz of this. and it will also decrease its size, weight and even its product parts cost. IMO. well im having a problem building audioguru's mod's shematic inverter but i got it worked. im not satisfied on its result. due to my small transfromer (1A) and only 6 2n3055.. i get a buzzing sound and i need to turn on/off for the buzz to wear off(this is my starter projects). and im still having a problem on its ic.. CD4047 .at first test.. it went ok.. after some trial and error... my ic CD4047 generates adnormal heat and my inverter dont work. i try replacing it with MN4047 (w/c they say its similar) and end up working again.. but... i take off the LM358 in the schematic and redirect the impluse to the 2SC1061. i got it work again. i but still... there are not much force to light an CFL.

nothing anusual..
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Binary 1011001101
Nobel Prize Winner

United Kingdom
569 Posts

Posted - Oct 24 2006 :  04:36:53 AM  Show Profile  Reply with Quote
I take it that makeing yourself a inverter isnt so simple. I found a really cheap inverter but it ran on 24V, is there a way to get 12V up to 24V at quite a high amperage 5A?
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