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PeeWee Inverter

Discussion in 'Alternative Energy' started by Tedfred, Nov 5, 2009.

  1. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    The four diodes are not needed.

    Just run the transistor bases right off the resistors coming from the control transformer.
    You will however need a blocking diode on the DC input to keep the circuit from feeding back to the DC source when its voltage drops below the transformers voltage.

    Your theoretically capable of doing a grid tie with what you have but expect its at best efficiency to be under 30% and probably less than that most of the time. The very small VA transformers are at the bottom end of the efficiency range to start with. Most transformers under 50 VA are well below 80% efficiency and at the few VA range 50% or less efficiency is not uncommon.

    Thats the down side to very small GTI design. Its inherent efficiency limits it severely and the possible energy transfer it can do is so small its cost avoidance pay back time is incredibly long. Being under 50% efficient at 10's of watts feed back is not practical from a usable energy stand point.
    But its a good way to start learning! :)

    However you will still need to add in the required control circuits and related other stuff. Uncontrolled GTI is bad bad thing! :eek:
    Granted at the power level your at now the background load on your home would stall it flat if the power goes out so right now its not really an issue! :D
     
  2. Mr RB

    Mr RB Well-Known Member

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    Well actually it is, because someone might unplug it from the mains and then touch the prongs on it's mains plug as it will still be outputting mains AC voltage into no load (so possibly higher than mains voltage).
     
  3. Tedfred

    Tedfred New Member

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    more on 5 watt peewee inverter

    I found a DIP adapter to use for the soldering of the tiny SOP chips for about $4.00, but I still need a lot more practices soldering. More latter.
    As to the 5 watt grid tie inverter. Thanks to Mneary, yes the two diodes feeding the pots are drawn in backwards. But they are placed correctly on my bead board model. And thanks to Mr.RB for answering a very poor phrased question. I will attempt to phrase my question more clearly. Using a 2 ohm resistor in series with the load, I get about .1 volts drop across the resistor with the higher voltage on the transformer side. As to the phase lag, if there is no load on the transformer there is minimal phase shift. And the sync transformer has minimal load, and can be reduced even more if I add one more stage of driver. Yes the out put transformer has a heavy load and there would be a current phase mismatch.
    Finally when the grid power is removed the two transistor moves too cutoff, shutting down the entire system, so there would not be a shock hazard. Thus the diodes. This eliminate the electrical receptacle gender defugalty mention earlier.

    I an unhappy with the large voltage swing on the output if output transformer is disconnected form the grid. (and sync transformer still connected to the grid) some kind of feed back nay be needed.
    AT this time I have some modifications that I have made and will post then if they prove out to perform better that what I have so fare.
     
  4. dave

    Dave New Member

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  5. MrElectro

    MrElectro New Member

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    A little help on 5 watt peewee inverter

    I found your project on the internet. I had to click on that "V-plug" to get to your project. What is with that?? At first it seems too simple to work. But with so few parts I could put something together and try it out myself. However your transformers valuses aren't marked on the semantic and I can't quit make out the writing in the picture. So I don't know what transformers that you are using. I not quit willing to invest my time is this project with out a little more details. So a parts lists would be helpfull.
     
  6. Tedfred

    Tedfred New Member

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    Here is a photo of 1 attempt at the 5 watt inverter. Although it did not produce the expected 5 watts, it did light up a 3 watt light. There are 4 light bulbs in the photo. on left is a clear 40 watt appliance light. This one is here to act like a fuse and only come on if there is a short or out of sync. The one next to it is a special 3 watt frosted bulb used on display signs. The @ off two one side are 9.5 and 5 watt Christmas tree lights. There is also a std 7.5 watt light not shown. Note the ganged adjustment pots above the 40 watt bulb. Near the top of the photo there is an AC to DC I.C. Chip. This was used in place of the Solar cells. I used a variac to maintain the 3.5 volts DC. The AC to DC I.C. Chip was over heating, so I add a heat sync to it. (the aluminum strip in photo neat top.) At that point I was able to get the 3 watt light to light. But at that point the driver transistor started to over heat. I messed around to long tiring different bulb sizes and roasted one of the transistors. The 40 watt bulb was on at full brightness at at point. The large transformer is a 220 volt to 6 volt CT. from digikey. The small signal transformer is something I pulled out of my junk box. I think that most anything here that will provide 60 cycles and enough current to drive the driver transistor would work. some parts from this project had been dismantled and recycled back to my jink box. If needed I can find the exact part numbers for the x formers use.
    Tedfred
     

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  7. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    I have been thinking about your design and although it sort of works its efficiency is very low and a few components need changing around.

    I tossed this together along with the Parts #'s for things that would likely match from Digikey. I think it could be built for around $25 or so. Probably less if you have spare parts laying around.

    Micro Grid tie Inverter.png
     

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