# dc to ac with 555

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#### bowser22

##### Member
hey guys im trying to run a sony house amplifer in my car (dont ask).It requires around 500watts.I was thinking of buying an inverter then i saw a homemade version made using a 555 and a transformer and some other components.Anyone have an idea of what the maximum current this can output if say a car battery is used?I was alternatively thinking of probing all the power connectors and making a circuit to supply the appropriate voltages so theres no dc to ac back to dc,im thinking this method would save power.
Thanks
''colin

#### Hero999

##### Banned
You haven't posted the schematic so we can't possibly tell you what the maximum power output is.

#### tcmtech

##### Banned
Realisticaly your far better off just buying a bigger sized factory made inverter unit and running it off that. When you do get a good car amplifier then you still have a good AC power source to do other things with.

Or go in eBay and buy a damaged Car audio amplifier or power inverters and fix it. Most often they have the power supply mosfets blown out or the output stage devices blown out. Both are easy fixes!

I picked up a pair of 2300 watt Audiobahn amplifiers for $100. Both had the power supply mosfets blown out from a dummy hooking up a set of jumper cables backward! Each amplifier cost me about$35 to fix!

#### audioguru

##### Well-Known Member
Well ,,,you see 500 watt is way too much for 555.. instead you can you another cheap ic ..4047 ..
here you can make 500 watt inverter..
500W low cost 12V to 220V inverter - circuit diagrams, schematics, electronic projects

you can alter its duty cycle to make Modified square wave ( to get a step closer to sinewave output results
That circuit has "corrections" from MP that makes it blow up.
For an output of 500W then the 2N3055 output transistors must conduct 25A each. But their absolute max allowed current is only 15A and they are poor above only 10A. It needs eight 2N3055 output transistors.
It has no spike protection diodes.
The resistor in the CD4047 oscillator has a value that is much too low then the value of the timing capacitor is much too high.
It uses two LM324 quad opamps instead of a single LM358 dual opamp.

#### ahmedragia21

##### Member
how much current can i draw from the above schematic ??

#### audioguru

##### Well-Known Member
The inverter with the 555 has an output power of about 60W. I think its voltage will change a lot with load current.

#### ahmedragia21

##### Member
how can i draw more current from DC voltage source that can deliver ???

#### audioguru

##### Well-Known Member
If you want an output POWER of 500W then the input POWER must be about 600W.

500W at 230V is an AC current of 500/230= 2.17A.
600w from a 12V battery is a DC current of 600/12= 50A.

#### ahmedragia21

##### Member
So the battery at the input should at least deliver 50AH ?

#### audioguru

##### Well-Known Member
So the battery at the input should at least deliver 50AH ?
A little 50Ah battery might not be able to provide a current as high as 50A or 60A. It can provide only 5A for 10 hours and 10A for 3 or 4 hours.

#### tcmtech

##### Banned
All the batteries I have ever seen have bolt or some form of lug teminals on them over about 12 AH give or take. A 50 Ah is the size of a good car battery and would have the large cable lug or automotive type battery terminals. I have standard UPS 7AH lead acid batteries with solder lugs that can put out over 80 amps and maintain 11.8 volts while doing it. But they do run down fast!
But a 50AH will have a much longer run time of course.

#### bowser22

##### Member
what? so your saying i can never run an amp of that size using a 12v car battery and an iverter.im also interested in just going right from the battery to the amp using regulators and other circuits

#### audioguru

##### Well-Known Member
People use high power car amps with the engine driving the alternator so the battery does not get destroyed. A car battery is made to start the engine in a few seconds, then be charged immediately. It is destroyed with a continuous high discharge current.
Some people use many deep discharge batteries in parallel.

A powerful home amplifier will not work from only 12V.

#### tcmtech

##### Banned
A good car battery does have an amp hour rating although its not usualy posted on it and they can run a fair sized load for a short period of 5 to 10 minutes with out damage but like audioguru said deep discharging a car battery is hard on it and can destroy it.
My dad used to buy the cheapest crapiest batteries he could find for the farm equipment. (because they constantly went bad, so why buy good ones?)
If they got ran down only a few times to the point of needing a jump start they would go bad!
However a good quality battery can take deep discharge occurances better as long as they get recharged immediatly. But still it is hard on them.
I personaly buy rather expensive dual use marine batteries for my work truck because I do run a big inverter (2000 watt cont 4kw surge) and fairly heavy loads for extended periods off it at times.
These batteries do have a good deep discharge capacity and a good cold cranking amp capacity too. They are like a starting battery and a deep cycle battery combined. But still they do go bad within a year or so from being run down too many times. (I love 60 month waranties!)
I have been around many higher wattage car audio systems and the ones that run for an extended periods of time use a second deep cycle battery or sometimes several. They can take deep discharge and not be adversely affected.

Running your 500 watt system should not be a problem for short times but it very well could ruin your battery if you get carried away too many times!

#### audioguru

##### Well-Known Member
The power from an amplifier depends on the music. If it plays acid rock which is full-power square-waves all the time then the power is the amplifier's rating or double.
Ordinary music has a average to peak power ratio of about 10 so if a 500W amp is just barely clipping the peaks then its average power is only 50W.
Modern class-D (switching) amplifiers are much more efficient than older class-AB amps and do not waste power by making heat.

#### Hero999

##### Banned
I don't think I've seen such an inefficient inverter.

There'll be a huge volt-drop on the voltage going into the transformer. The output transistors in the 555 will drop a couple of volts, Q1 and Q2 will drop another couple of volts. To get the full 230V, you'll need a 12V supply and a 3V transformer.

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