dc to ac

[wasssup1990]

Hi, how do you convert dc to ac. PLEASE EXPLAIN IN DETAIL.

 

[kinjalgp]

Conversion of DC to AC can be achieved using oscillators. Oscillators can be of two type: Sinusoidal or non-sinusoidal (square or any other). Some of the sinusoidal oscillators are Colpitts Oscillator and hartley oscillator. bot these have some advantages and disadvantages. And among square wave oscillators is the astable multivibrator. For getting high power AC from these oscillators, amplifiers are used along with step up transformers to increase current and voltage levels.

 

[wasssup1990]

Could you explain more simpler or could you explain a different way that is simple.

 

[Sebi]

The circuit always depend from Your application.
- desired output power
- output frequency
- input DC voltage
- you need galvanic isolation or not

 

[wasssup1990]

The reason why i need the dc to ac conversion is because i am trying to build my own inverter. I have only got the the step up transformer, from 15v to 240v. Then I found out that transformers only work on ac.
I am wanting to power appliances from little portable fans to a 2400W heater.

 

[bogdanfirst]

how do u imagin u can get to power a 2400W heater form fans?
think......that's about 10A @ 240V...
if u want to produce 2400W from 15 v fans think
u need 160 amps........and run this trough a transformer and get 10 amps
r u sure thats what u want to do? get power from fans to a heater?

 

[wasssup1990]

NO! I am powering it from a knokia phone battery.

 

[herbymcduff]

so what you are wanting to do is take that Nokia battery, and power an inverter(not a digital one), to convert the 15vdc to 15vac, then run it through a step-up transformer to go from 15vac to 240vac. And then be able to run small portable fans, or even a 2400W heater. Is that in general of what you are trying to achieve? :?

 

[wasssup1990]

Thats exactly what i mean!!

 

[herbymcduff]

I checked and checked, but couldn't find really anything. Now there are alot of inverters on the market, some even a greater size then you wanted, but cost money. And you can't build them yourself. But I did find this, and maybe of some interest to you to get started on your project.

http://www.electronics.50g.com/cdcac.htm

Hope it helps.

 

[kinjalgp]

Before proceeding keep one thing in mind that in any circuit
Power Input ~= Power Output. So if you want 2400W output power you need 2400 or a bit more of power to be fed to your inverter. A Nokia battery won't even light up a 230V/50W bulb for 5 minutes.

 

[bogdanfirst]

i agree with tahat kinjal, to get 2400W..its really hard.....
and you would have to use a hell of a transformer.....
i dont think you might get that power from a car battery....the current neeeded schould be ~200A and cosidering that a normal car battery has a capacity of 40-60Ah you would power it for only a few minuters before the battery would be dead

 

[wasssup1990]

Ok maby 2400W was a bit to much what about 500W. Any ideas?
Just to know that the Nokia phone batt kept a camera flash circuit going for about 4 hours, and it was powering a neon lamp.

 

[bogdanfirst]

if you want 500W think ...........
if you have a 12V car battery with the capacity of lets say 60Ah, and you draw 500W from it it would last about 90 minutes....
i think that you dint understand the basic electronics.
when you use an inverter you dont get more power than it comes out of the battery, you get even less. the only thing that cheanges is the voltage-it increases...
something useful would be to tell us what it is written on the battery..the volatge, capacity(Ah or mAh) and other things that are written on it.
and thing that for 500 watts you would need a transformer that would support 45A at the primary!!!!!!!!!!!

 

[sam_h]

I don't know if this will work but what if you try using a NE555 @ 50Hz to a op-amp that will handle high frequencys this way you should (in theory) be able to acheive a astable current going from +Ve to -Ve and maybe you'll be able to put a transformer to that.

I don't know whever that'll work at the currents which you what or work at all. If any one has any information to tell me why this wouldn't work please let me know.

 

[kinjalgp]

Yes that will work. But for simplicity you can use op-amp itself in astable multivibrator configuration. And let me tell you one thing 50Hz is not considered a high frequency as you have mentioned for the op-amp.
For high current, a push-pull amplifier stage consisting of high power transistors/MOSFETs will be required to drive the transformer.

 

[sam_h]

Re:kinjalgp

Thanks kinjalgp I'm new at this and any feedback is much appreciated

 

[ampedtech]

You need to start at the beginning.
P=I*E and E=I*R .
These equations are for DC. The trend in the USA is to also use them for AC, but ONLY for estimating.

P= power (Watts
I= current (amps
E= voltage (volts
R= resistance (ohms

Truth: Power in can not exceed power out.
You already know this. Make a pendulum with a string and a weight (mass). When the pendulum is set into motion it can not ever go higher than its launch point. Another interesting point is that without outside influence the motion will decay. If the mass on your pendulum had a mass of 1kg and the length of the string was 1 m and midway through it's swing it struck your automobile you might chip the paint maybe even dent it. If the mass was 1000kg you may knock the car off it's wheels.


Conceptualize: When your phone battery, is providing the absolute maximum power that the phone could possibly demand P would be less than one watt.
Find a low wattage light bulb, 10 watts or less. Can you hold your hand on it? Try (don't try) that with a 100 watt bulb.

I'm rambling. The battery you want to use does not have the capacity to do what you want. I do not think that the battery could even provide 10 watts without damage to itself. At 10 watts or more the battery could even be explosive.


Get yourself a Volt/ohm meter, a small battery (12 volts) and a couple of light bulbs (try a 12v car signal or brake light). Learn how to take resistance, voltage, and current measurements. Try different configurations with this setup. (series and parallel with the light bulbs). See what happens, take notes, make a table of voltage, current, resistance, calculated power, and brightness for each bulb for each configuration.

Rap up:

You need to start at the beginning.
Arm your curiosity with knowledge.
Have fun.
Be safe.
Make cool things.

 

[kinjalgp]

These equations are for DC. The trend in the USA is to also use them for AC, but ONLY for estimating.

Ohms law is applicable for both AC as well as DC. The only power equation is different for AC i.e P=V*I*Cos(PHI)
Cos(PHI) is the power factor and is only considered when Inductive or Capacitive loads are present in the circuit. For resistive loads Cos(PHI)=1, so it is neglected and therefore the Power equation becomes same as for DC.

Another thing....

Truth: Power in can not exceed power out.

IT should be other way round: "Truth: Power out can not exceed power in."

 

[ampedtech]

kinjalgp,

Another thing:
you'd be right, power out can not exceed not exceed power in.

What was I thinking? (don't answer that)