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Availbale Products, Material- and Service suppliers => Do It Yourself => Topic started by: UTiLeeTY on February 17, 2012, 10:37:39 AM

Title: How to ... transform DC to AC?
Post by: UTiLeeTY on February 17, 2012, 10:37:39 AM
Hello dear OU members :),

... actually, I am not an electrical engineer but I would like to know your professional opinion on what (self-made) concepts for DC to AC conversion do exist and how you can build them :).

Basically, what is needed:

any input DC into same(!, or even close) AC.

Many thanks for your participation
... & finally your are speeding up my open source project that way ;) (so, we all may profit from that).

Best wishes,

UTiLeeTY

Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 17, 2012, 04:04:31 PM
power inverter, inductive or capacitive step up.
 does it have to be sine?
 can it can also be modified sine.
 how powerful it needs to be do you want to burn a small 15 watt bulb or do you want to power your 2000 Watt oven with it.
these things are important to know before designing such a circuit because the rating of the parts is critical and it is directly related to the maximum amperage on the primary circuit.


Thank you for quick reply :) ,

... well, I've tought of maximum 12VDC and 1A input, which should be transformed to 12VAC ... & 'modified' to turn on/off or switch a coil which works with magnetic fields & is doing work...

But basically, that 'invertor' circuit need to work under load usually in 0.01-1V range, DC input may vary quite often.

I guess, it should run on 1:1 DC->AC power invertor, which I am aking for :) . Not really need to be sine waves, as long as current stays the same (as before 'inversion'; current increases are very welcome).

Thank you for your effort :) .

Sincerely,

UTiLeeTY
Title: Re: How to ... transform DC to AC?
Post by: gyulasun on February 18, 2012, 10:43:33 AM
hello UTiLeeTY,

Here is a schematic, a bit similar to what microcontroller described:

http://electroschematics.com/220/12v-dc-220v-ac-converter/ 

IT works with squarewaves and you have to find a transformer which has to have a fourth winding with also a 9 to 15V output voltage, besides the 220V (or 120V) output.  Or you can wind this fourth coil onto the core yourself if you cannot find such.Or you use a second transformer to convert the 220V (or 120V) output of the first transformer back to your lower output needed.

cheers,  Gyula
Title: Re: How to ... transform DC to AC?
Post by: Rafael Ti on February 18, 2012, 11:46:26 AM
And a little bit more complicated, but PWM ;D , which means having sine wave output. It's based on SG3524. As for me very interesting.

http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/ (http://www.instructables.com/id/250-to-5000-watts-PWM-DCAC-220V-Power-Inverter/)
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 18, 2012, 12:02:58 PM
Thank you all for really interesting recommendations :),
 
 ... but actually, I don't need more voltage out as it is coming in.

Would you, please, ... convert those circuits in way that they transform
input DC voltage into (near) same output voltage and post them ^^?

And: that idea with a transformer sounds really good :) ... please post diagramm :).

Your help is very welcome :).


Many Thanks,

UTiLeeTY

 
Title: Re: How to ... transform DC to AC?
Post by: Groundloop on February 18, 2012, 12:34:26 PM
@TiLeeTY,

The attached circuit will give you what you want. Just remember to drive the input part from
a separate power supply than the mosfet switch part at right in the drawing. If you run
the +DCV from 12 volt then you will get 12 volt AC (square pulses) output. This circuit
can drive coils and transformers (inductive load) if you want to. The oscillator input can
be from a function generator or a 555 oscillator circuit. The 555 IC should be a type
that can handle 12 volt DC so that you get 12 volt pulses to the input of the bridge.

If you need a circuit drawing for a 556 IC oscillator with frequency and duty cycle control,
then let me know and I will post a drawing here.

You can use almost any type of mosfet transistors of the N-Type on the switching part.
Just make sure your mosfets will take the voltage and current you plan to use on the switch.

GL.
Title: Re: How to ... transform DC to AC?
Post by: Rafael Ti on February 18, 2012, 01:37:52 PM
Or... you can try something easy to do first :) . In here the output AC is square or even triangle due to use of C4, but you stated you don't need a sine. Its level depends directly on supply voltage, which is your input voltage. Transistors can carry up to 6 Amps, so you better put a 5A or less fuse on output and that will be the max. current you can get. This setup originally drives a transformer with single primary winding.
Title: Re: How to ... transform DC to AC?
Post by: gyulasun on February 18, 2012, 01:56:00 PM
Hi UTiLeeTY,

I have made a schematic from the link I gave you above, including the second transformer I wrote.  Of course you have to know a single transformer with just the correct number of turns on its output side is the preferred solution but you have to wind it I am afraid.

The BD699 type (Darlington) shown in the original circuit is not easy to find but you can use a TIP3055 type (no real need for Darlington type) or similar NPN power transsistors with 70V or higher collector voltage and 7 - 8A or higher collector current ratings. 

Now you have some choices to build...   lol

Good luck,
Gyula
Title: Re: How to ... transform DC to AC?
Post by: Groundloop on February 18, 2012, 02:11:13 PM
@TiLeeTY,

The attached 556 oscillator gives you control of both frequency and duty cycle.

GL.
Title: Re: How to ... transform DC to AC?
Post by: Groundloop on February 18, 2012, 08:05:44 PM
Hi UTiLeeTY,

I have made a schematic from the link I gave you above, including the second transformer I wrote.  Of course you have to know a single transformer with just the correct number of turns on its output side is the preferred solution but you have to wind it I am afraid.

The BD699 type (Darlington) shown in the original circuit is not easy to find but you can use a TIP3055 type (no real need for Darlington type) or similar NPN power transsistors with 70V or higher collector voltage and 7 - 8A or higher collector current ratings. 

Now you have some choices to build...   lol

Good luck,
Gyula

@gyulasun,

Here is a little improved circuit of what you posted. The two transformers will use up a lot of energy because
of losses in the transformers. Same goes for using npn power transistors. So I recommend using mosfets instead.

Regards,
GL.
Title: Re: How to ... transform DC to AC?
Post by: gyulasun on February 18, 2012, 09:59:30 PM
@gyulasun,

Here is a little improved circuit of what you posted. The two transformers will use up a lot of energy because
of losses in the transformers. Same goes for using npn power transistors. So I recommend using mosfets instead.

Regards,
GL.

Hi Groundloop,

Thank you for the modifications I fully agree with them!

Greetings,  Gyula
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 19, 2012, 11:32:05 AM
Whoa! Thank you for awesome curcuits :D!

But, how could I manage to regulate 'AC impulses' from say ...
an AC generator coil, which then go into one of both transistors (say: NPN on & PNP off - positive, NPN off & PNP on - negative) and produce output voltage depending on "polarity" of outgoing FET?

Thank you for your time & curcuits :).

UTiLeeTY 

Title: Re: How to ... transform DC to AC?
Post by: poynt99 on February 19, 2012, 02:54:38 PM
Whoa! Thank you for awesome curcuits :D !

But, how could I manage to regulate 'AC impulses' from say ...
an AC generator coil, which then go into one of both transistors (say: NPN on & PNP off - positive, NPN off & PNP on - negative) and produce output voltage depending on "polarity" of outgoing FET?

Thank you for your time & curcuits :) .

UTiLeeTY

Sounds like you will need to stabilize your input first, and you can do this by full wave rectifying and filtering (large capacitor) the fluctuating input. Then you'll have a more stable DC source to start with.

To now convert to AC, you can either do so using a cheap and dirty inverter, or have the DC source power a function generator that is run through an amplifier stage. It depends on how clean an AC voltage you want, and what frequency. With a function generator/amplifier, you have more flexibility in controlling the output amplitude, frequency, and type of wave form.

.99
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 19, 2012, 02:55:03 PM
If you want be able to regulate or control the output voltage i suggest you use a microcontroller with PWM function you can control the output voltage.
but now i'm totally lost as to what you want to do so i'm out.

Hmm ... I just want to use a NPN and PNP transistors as switches, which do work one after another ...

A rectified (by diode) AC generator coil/s current should be my input on FET for turning on or off an available DC voltage (such as 12VDC from battery).

Like,   a) PNP is off, 2nd AC input is off & NPN, using 1st rectified AC input, is on
          b) same NPN do create positive (12VDC) pulse
          c) then NPN goes off (because of no 1st AC input) & now PNP goes active mode
              (because 2nd AC input is on)
          d) same PNP produces negative (12VDC) pulse
          e) go back to a) 

In theory, that should work well ... but how may I import that into a working circuit, please :S?

Best Regards,

UTiLeeTY
Title: Re: How to ... transform DC to AC?
Post by: Groundloop on February 19, 2012, 05:18:18 PM
Hmm ... I just want to use a NPN and PNP transistors as switches, which do work one after another ...

A rectified (by diode) AC generator coil/s current should be my input on FET for turning on or off an available DC voltage (such as 12VDC from battery).

Like,   a) PNP is off, 2nd AC input is off & NPN, using 1st rectified AC input, is on
          b) same NPN do create positive (12VDC) pulse
          c) then NPN goes off (because of no 1st AC input) & now PNP goes active mode
              (because 2nd AC input is on)
          d) same PNP produces negative (12VDC) pulse
          e) go back to a) 

In theory, that should work well ... but how may I import that into a working circuit, please :S?

Best Regards,

UTiLeeTY

@UTiLeeTY,

Why don't you make a simple drawing on what you want to do?
A drawing says more than 1000 words. :-)

GL.
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 19, 2012, 07:43:28 PM
You want two 12v pulses, one when the sine tops and the other when the sine bottoms is that correct?

So you want to synchronize your output pulses with your input signal is that correct?


okay i get it you have AC signal to start with.
You want two 12v pulses, one when the sine tops and the other when the sine bottoms is that correct?

So you want to synchronize your output pulses with your input signal is that correct?


 Yes :),
 
 exactly, it should run like that:
 
 there you do have 2 (rectified AC) coils for switch input, one attached to NPN and another goes into PNP transistor, 12 VDC battery and couple resistors.
 
 Then, if 1st AC coil gives an impulse (on/off) to NPN -> (+/-)12VDC pulse is active 
           if 2nd AC coil gives an impulse (on/off) to PNP -> (-/+) 12VDC pulse is active
 
 That way one can modulate an AC depending on active or inactive AC coil pulses.
 
 I just dont know how to connect them properly >_<, hope you can help :).
 
 Best wishes,
 
 UTiLeeTY
 
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 20, 2012, 02:53:18 PM

If you decide to go with NPN and PNP you just turn around the diode so the target gate threshold pin get's a negative or a positive pulse.
Also be careful not to burn out your components because when a trigger winding is placed next to the output coil it will quickly destroy itself.

May I ask for a circuit diagramm, please :) ?

Edit: What would happen, if I simply connect 2 (rectified via diodes in 1 direction OR without diodes?) wires of a coil to the base of NPN transistor (as an positive input going through/no diode & connected to the base -> then outgoing wire of same coil from the base of NPN through/no diode to negative pole of a coil :O )?

Many Thanks,

UTiLeeTY
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 22, 2012, 07:47:57 PM
Hello again :),


that one is what I was looking for \ 0 / :

http://www.falstad.com/circuit/e-mosfollower.html

Thanks for epic links :thumbsup.

Now my questions:
- how may I even out -VAC and +VAC in that circuit (say -7V & +7V, sine wave)?

- is there a chance to build the same using NPN and PNP transistors?

Many Thanks  8) ,

UTiLeeTY
Title: Re: How to ... transform DC to AC?
Post by: Rafael Ti on February 23, 2012, 07:47:56 AM
Hi UTiLeeTY
Maybe u need a simple AC emitter follower? There are two types of this setup; with single supply voltage or with two supplies +Ucc and -Uee.
Title: Re: How to ... transform DC to AC?
Post by: UTiLeeTY on February 23, 2012, 02:54:49 PM
Hi UTiLeeTY
Maybe u need a simple AC emitter follower? There are two types of this setup; with single supply voltage or with two supplies +Ucc and -Uee.

Thank you for circuit, need to try that out later :).

Well, ... which one would you prefer for switching duty in your circuits:

Hall effect sensor

OR

Reed switch?

Like before, I plan to use my circuits under maximum 12VDC and 1A load
at frequency ... < 500Hz.

Thank you very much :).

UTiLeeTY
Title: Re: How to ... transform DC to AC?
Post by: Rafael Ti on February 23, 2012, 04:26:00 PM
Well, ... which one would you prefer for switching duty in your circuits:
Although some reed switches can operate up to 500 Hz I would suggest you to use the hall effect sensor. Just because of frequency. I think 500 Hz is to high for mechanic switches especially when they work continuously... Also using some types of hall effect sensors you can determinate the N & S pole of magnetic field and its sensitivity, which is impossible for reed switches.
Title: Re: How to ... transform DC to AC?
Post by: tabeta_03 on March 18, 2013, 11:10:59 PM
@TiLeeTY,

The attached 556 oscillator gives you control of both frequency and duty cycle.

GL.
Hello dear Groundloop and all ou members
I have a mini incubator at home that is working whit 12 volt AC - 1.5 amp and 10 watt this incubator has Thermoregulator borde&heater&Fan&Gear .i am trying to turned it on with 12v DC -5amp dry-cell battery but i need a 12v DC to 12v AC inverter and I made your attached 556 oscillator but that output is not AC i should connect pulse out to what for 12 volt and 1.5 amp ac output? I am not an electrical engineer i only connected the Parts form your map.pleas complete this attachment to 12vAC output for me.i love u and internet that i can connected to u whit it. :-*
Title: Re: How to ... transform DC to AC?
Post by: tabeta_03 on March 18, 2013, 11:12:20 PM
@TiLeeTY,

The attached 556 oscillator gives you control of both frequency and duty cycle.

GL.
Hello dear Groundloop and all ou members
I have a mini incubator at home that is working whit 12 volt AC - 1.5 amp and 10 watt this incubator has Thermoregulator borde&heater&Fan&Gear .i am trying to turned it on with 12v DC -5amp dry-cell battery but i need a 12v DC to 12v AC inverter and I made your attached 556 oscillator but that output is not AC i should connect pulse out to what for 12 volt and 1.5 amp ac output? I am not an electrical engineer i only connected the Parts form your map.pleas complete this attachment to 12vAC output for me.i love u and internet that i can connected to u whit it. :-*
Title: Re: How to ... transform DC to AC?
Post by: Groundloop on March 19, 2013, 04:37:34 PM
Hello dear Groundloop and all ou members
I have a mini incubator at home that is working whit 12 volt AC - 1.5 amp and 10 watt this incubator has Thermoregulator borde&heater&Fan&Gear .i am trying to turned it on with 12v DC -5amp dry-cell battery but i need a 12v DC to 12v AC inverter and I made your attached 556 oscillator but that output is not AC i should connect pulse out to what for 12 volt and 1.5 amp ac output? I am not an electrical engineer i only connected the Parts form your map.pleas complete this attachment to 12vAC output for me.i love u and internet that i can connected to u whit it. :-*

tabeta_03,

The output from the 556 oscillator is not AC, you are 100% correct. You need to build the H-Bridge circuit also
and use the 556 oscillator as a input to the H-Bridge. The output of the H-Bridge will be 1/2 of the frequency
of the 556 oscillator. So your goal is to tune the 556 oscillator to 100Hz (or 120Hz) to get 50Hz (or 60Hz)
output from the H-Bridge. The output of the H-Bridge will be pulsed DC.

GL.
Title: Re: How to ... transform DC to AC?
Post by: forest on March 19, 2013, 06:20:25 PM
I heard that it's possible to get very nice clean 50Hz AC pure sinewave using 4 mosfets bridge with a microcontroller setup. Is that true ?
Title: Re: How to ... transform DC to AC?
Post by: Groundloop on March 22, 2013, 06:08:55 PM
tabeta_03,

Here is the updated H-Bridge switch using the IR2111 driver.

GL.