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Thread: My mini linear power supply..

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    My mini linear power supply..

    Okay, I had this GREAT idea.. right?? to put a linear DC-DC PS into an old HD case.. and use the case for a heatsink.. does anyone see any problems with this??? the case should provide enough of a heatsink to draw 3amps continuous@5volts and 1.5continuous @ 12volts.. right??? this should ha enough to power a mobo, with external cards (2 or so) and a harddrive...... This idea would provide easy mounting of the powersupply.. and prevent shorts of the PCB, as you probably wouldn't need one... anyway, post your feedback, positive and negitive.. thanx..

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    Retired Admin Aaron Cake's Avatar
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    Sounds like a good idea to me, but don't waste time with linear. A switching supply would be best, and the form factor of the HD would allow a small fan to draw air through the whole case...
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    Well, I made one, using linear regulators, in a LAPTOP HD CASE!!! LOL!!!!!!!! works fine... only prob is that I was originally gunna use 2 5amp 5volt regulators, but using one generated ZERO noticible heat.. so, I am gunna rip out one of teh 5volt, and replace it with another 12volt low dropout (only rated @ 1amp) so as to have 2amps constant on teh 12volt, rather than 1amp, with I had and powered a HD, 48X cdrom, and a fan, and then something started smoking, lol... ahh, time for some pics I suppose, DODGY DIGITAL CAMERA!!!!!!! (not mine) (don't have one)



    The masking tape on teh PS is becaseu I nolonger had teh screws.. Also, I thought I would pointout that I have ZERO sucsess in teh past with using 1084 12volt regs to give me a regulated output, even with input of around 14volts... This is why I chose lower power regs which give a regulated output of 11.8 volts with as low as 12.2 input... and, as teh volatge drops, teh output is teh same is the input, but with the 1084 regs, I got a drop of around 1volt between out and in when a lower input was used.. so, with this setup I am using, when cranking, teh battery voltage drops to no less than 10.5volts... this is therefor what the 12volt rail then is, and this is actually still enough to SPIN UP a hd, not just keep it spinning.. so, andone in Australia want to buy a sproggy PS without half teh diodes (I was unable to source these, or afford them, after my money went missing in teh post... lol)

  4. #4
    Rob
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    Originally posted by THEMP3KID
    I have ZERO sucsess in teh past with using 1084 12volt regs to give me a regulated output, even with input of around 14volts
    Did you have a LF decoupling cap on the input & LF & HF decoupling caps on the output? These can make quite a bit of difference, especially the LF on the input.

    Rob
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    Do you have the part numbers of the regulators you used? Also, do you have a wiring diagram? Thanks, that is exactly what I am looking for, 5V 5A and 12V 1A...

    mike

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    Originally posted by Rob


    Did you have a LF decoupling cap on the input & LF & HF decoupling caps on the output? These can make quite a bit of difference, especially the LF on the input.

    Rob
    Ahh..... I forget now, lol..

    Well, the regulators I used were......
    Hasn't this all been covered before or something??? anyway.. thay were:

    5volts -
    LM1084-5

    12volts - LM2940C - 12

    Or something like that, not too sure on teh 12volt one, but teh specs are right... can't check part number on teh ic now, can't find the PS.

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    Thanks..

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    Okay, I swapped one of the 5volt regulators for another 12volt regulator, but now I need 2 resistors to balance the output voltages... Will post results soon....

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    Retired Admin Aaron Cake's Avatar
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    Have you run a PC for any length of time with this supply? What was the heat output? I would be concerned that the HD case will simply act like thermal storage, and keep heating up without any real transfer to the air. Might be a good idea to bolt on an old CPU heatsink to each side...That will give more surface area and help keep the temp down.
    Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
    Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
    "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

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    Well, I powered a HD a cdrom and a fan for about half an hour, and then something started smoking, this was before I had 2 12volt regulators.... The HD case was evenly warm, and I couldn't even tell which chip was creating the heat, so it must conduct heat well.. Some time soon I will try it with the computer.....

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