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Thread: Anyone tried this hairbrain scheme?

  1. 03-06-2002, 04:37 PM #1
    waltsongs
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    Question Anyone tried this hairbrain scheme?

    Has anyone tried this? I am going to try to rewind the transformer in my inverter circiut to obtain 5 to 6 VAC at 8 AMPS and two 10-12 VAC at two Amps, then use typical linear circuits to get +5 +12 -5 -12 DC. See the circuit at: http://waltsongs.tripod.com/hairbrain.html
    I have all the stuff lying around, figure I might as well see if it works.

    Walter Farmer
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  2. 03-07-2002, 09:53 AM #2
    Aaron Cake
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    Go ahead, but I doubt it'll work. You can't use 1N4002 diodes in that circuit, you need the HEP154 (or whatever they are). The 2N3055s are not going to be able to sink enough current. And since you will need to use linear regulators to regulate after it comes from the transformer, you will be wasting alot of power as heat...It has been proven that linear regs are unsuitable for powering a computer.
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  3. 03-07-2002, 11:07 AM #3
    waltsongs
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    The only reason I would try it at all is I have all the stuff lying around. If I can wind the secondary to about 5 volts AC it should rectify to about 7 volts. Now if I draw 8 amps through the linear regulator I only dissipate 16 watts, that seems a reasonable number to me. I am also going to play with the inverter caps to crank up the frequency and see if it works more efficiently. I do not have to worry about having 50 to 60 Hz. I'll probably just end up with a car full of smoke, but hey, nothing ventured nothing gained.

    Walter Farmer
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  4. 03-08-2002, 09:42 AM #4
    Aaron Cake
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    Where to find a linear regulator that does 8A? Most max out at 5A, but I guess there's no reason they can't go higher.

    Basically, I just don't want you to waste your time. If you want to build a supply like this, replace the heavy 60Hz transformer with a light toroid unit and use an oscillator based on the 4011 or 555 timer or even a PWM chip. Then you can regulate using linear.
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  5. 03-08-2002, 11:06 AM #5
    waltsongs
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    I would use pass transistors to up the regulator current. Your advice is well taken. I discovered last night that my mother board will boot up and play without -5 or -12 so I'm re-thinking my plan. My display card seems to work fine without -5 or -12 also. This simplifies things a bit. I'll post here again when I have something that works.
    I'm still interested in finding a DC to DC solution that can be built from Rat Shack parts. If I stumble on something, I'll post it here.

    Again,
    Thanks
    Walter Farmer
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  6. 03-09-2002, 10:48 AM #6
    Aaron Cake
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    Talking

    Cool. I'm really interested in seeing the result. I actually was going to do something like this a few years ago, but then switched to a higher frequency osc and a toroid transformer. Never did finish it though.
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