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Motionless Passive Generator. What do you think?

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blackwoolf511

Mon Jun 04 2012, 01:02PM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
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Posts: 17

ok sorry?

brandon3055

Mon Jun 04 2012, 04:02PM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

This is a circuit that has worked for me in the past its not sign wave but it should be good if you are a new to all this (sign wave is much harder to achieve)

there are plenty of others out there just do.a Google search for 12v to 120 or 240v inverter circuit and for the transformer if you want high current I recomend rewinding an MOT but that might be something to think about in the future (when you have a better understanding of what you are doing

Conundrum

Mon Jun 04 2012, 07:25PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Reverse biased transistor oscillator?
Quick and dirty, plus works with nearly any cheap transistor even ones that have had the base lead snapped off during removal.

Another variant is to use a "cooked" silicon diode or infrared LED as a ghetto tunnel diode.

If you want something reliable, I'd use the classic Royer circuit with MPSA42's to tolerate >300V collector voltage allowing a decent input to output ratio.

Patrick

Mon Jun 04 2012, 11:12PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Blackwoolf, what do you mean by "pure sine wave" in that block in the picture near that rectifier diamond?

You can approximate (to a very close degree, nearly perfect, 99.999%) a sine wave using the methods suggested like the look up table, from a PWM driven H-bridge. (a perfect sine wave is not required for most modern electronics, though there are reasons to require sine quality)

these can be made to work quite well, ZPE garbage need not be included.

blackwoolf511

Tue Jun 05 2012, 12:11AM

Registered Member #4278 Joined: Tue Dec 20 2011, 09:03PM
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Posts: 17

With "pure sine wave" i meant: a sinewave clean enough to could run electronics as PC, HD TV and so on without damaging them. I've red on the www that for "sensible" electronics i need a sinewave signal as clean as possible(almost perfect), otherwise if there are RMS or distortion of the signal the life of this electronics get shorter and they risk to burn from this.
I saw on ebay some inverters but they cost too much and one has no guarantee if they are so qualitatively as their resellers pretend to be.

Neet Studio

Tue Jun 05 2012, 02:31AM

Registered Member #4037 Joined: Fri Jul 29 2011, 03:13PM
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Sine wave, square wave, triangular wave, it doesn't care. It doesn't care about the waveform because the AC (50/60Hz) is rectified into DC to run a switch mode power supply. May be some low pass filter to attenuate the higher frequency components?

If the AC were fed directly to an old iron core transformer, it might make a difference.

brandon3055

Tue Jun 05 2012, 04:06AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

Neet studio I always thought the same thing untill my dad tried to run a plasma tv off of a 1000W (modified sign wave) inverter it went completely nuts and made a really loud noise luckily it didn't damage it

Edit: maby its got something to do with the rectification wear as rectified mains gives you 300ish vdc maby rectified sqair wave gives you something completely different

Patrick

Tue Jun 05 2012, 04:37AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

blackwoolf511 wrote ...

With "pure sine wave" i meant: a sinewave clean enough to could run electronics as PC, HD TV and so on without damaging them. I've red on the www that for "sensible" electronics i need a sinewave signal as clean as possible(almost perfect), otherwise if there are RMS or distortion of the signal the life of this electronics get shorter and they risk to burn from this.
I saw on ebay some inverters but they cost too much and one has no guarantee if they are so qualitatively as their resellers pretend to be.

as long as it has a modern SMPS, then you dont need even a sine at all, though there are some motors and transformer types that really need good sine waves, modern electronics can usually take any undulating wave. However, if you approximate the sine wave or generate a "supposedly perfect sine wave" you still have to be sure that your load doesnt cuase distortion due to a lack of a PFC circuit.

mister_rf

Tue Jun 05 2012, 06:48AM

Registered Member #4465 Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145

@blackwoolf511

Itâ€™s so funny the whole daisy chain wiring, remind me about this cartoon picture:

Mattski

Tue Jun 05 2012, 07:58AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Destroyer of mosfets wrote ...

Neet studio I always thought the same thing untill my dad tried to run a plasma tv off of a 1000W (modified sign wave) inverter it went completely nuts and made a really loud noise luckily it didn't damage it

Edit: maby its got something to do with the rectification wear as rectified mains gives you 300ish vdc maby rectified sqair wave gives you something completely different

A rectified 120V sine wave gives a peak of 169VDC, though when rectified and filtered the ripple on the filter capacitors can (and generally should) reduce this somewhat.

wrote ...
Itâ€™s so funny the whole daisy chain wiring, remind me about this cartoon picture:

Hehe, I'm sure I'm not the only one here who had a similar idea as a kid. I thought about it in terms of running airplanes with a windmill on them. My parents tried valiantly to explain why that wouldn't work.

A fully square wave inverter tries to put out 120Vrms, which results in a peak voltage of only 120V. Most modern SMPS will be fine with that. Any resistive load will be fine with that. Inductive loads i.e. motors or transformers will be a bit unhappy as the flux (proportional to volt-seconds applied to the winding per half-cycle) is larger for the same RMS voltage. Whether it causes a problem depends largely on how much core margin is in the design.

I think most inverters are modified square wave with some dead time between each half-cycle to improve the harmonic distortion and make it slightly closer to a sine wave. The peak voltage is a bit higher, and it lowers core flux for inductive loads compared to the square wave without dead time.

A modern universal input SMPS should be able to deal with any of these, resistive loads are totally fine. I think the main reason for pure sine wave is for driving inductive loads or for grid-tied inverters.

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