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Thread: you dont necessarily need a voltage regulated PSU

  1. #51
    FLAC
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    Well, the mini-box 200W psu's allow for 12A on the 12V rail (peak of 13.5A) so that's 144W of power for the cpu. From what I've found the power usage of my 2500+ XP Barton is somewhere around 60-90W so I may well be ok with the mini-box psu. However, the 120W solutions I was thinking about are clearly out of the question. Well, that makes choosing a lot easier - I now only have to choose between long and thin or short and wide.

  2. #52
    FLAC
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    Quote Originally Posted by justICE
    oon you will start calculating if the 500 bucks it will cost you would be offset by the opus 150, that barton, and your mobo. Hehe your probably doing that right now.
    Note quite, but close . Let's see:
    m/b + case (to scavenge metal & switches from) $20 (already have)
    AMD 2500+ XP cpu - $67 (already have)
    512Mb non-low profile memory - $25 (already have)
    160Gb Seagate Barracuda HDD - $60 (already have)
    slimline cd with 40 pin converter - $0 (already have - may not bother putting in)
    Custom case - $20 (some plexiglass from home depot + bits from the old case)
    USB hub - $0 (already have)
    USB gps - $0 (already have)
    PW-200-V - $50
    7.2Ah tank battery - $10
    Some diodes (may want to isolate the switched 12V line from the 7.2Ah tank battery) - $10
    Total - ~$262
    Total without the bits I already have - ~$90
    Not being ripped off for an overpriced, oversized Opus - priceless

    Let's just hope I can make it work . It should be a *lot* cheaper than the via route (partly because I'm using bits I already had) and more powerful but a lot more of a power hog which probably leads to lower mpg . The cost of the VIA approach was in the region of ~$500 with memory, case, laptop hard drive (and possibly a slimline cd). I'm only paying $147 for my solution if I can make it work - possibly $217 if the via estimate included the psu (can't remember).

    Plus, it's more of a challenge this way...

  3. #53
    FLAC
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    Quote Originally Posted by justICE
    Also, I could not find a "safe" range for the 12V rail in the tech documents at amd (they assume everyone uses the standard atx ps) so I asked the tech support. I will post when they reply.
    Did they ever respond?

    I've been re-reading this thread. Wow was I naive with some of those earlier comments!
    Progress: 80% - Permanent install left.
    Motion LS800 Tablet PC and dock.
    Vista, Bu-535 GPS, RoadRunner, MPT2006.

  4. #54
    Low Bitrate
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    No haven't heard anything. I got a reply back saying I need to apply for a nda but it required me to find a local retailer and sign some forms. Unfortunately, I have been spending "normal working hours" at my job so I haven't had a chance. One of the guys over there in the tech forum said he ran some tests and the cpu became extremely unstable at 11.5V. He did not test the high side because he didn't want to break his processor.

  5. #55
    Raw Wave
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    Quote Originally Posted by justICE
    One of the guys over there in the tech forum said he ran some tests and the cpu became extremely unstable at 11.5V. He did not test the high side because he didn't want to break his processor.
    Yup, its not surprising at all, alot of poeple here seems to think that just because the PC did not reboot then everything is gonna be ok.

    I have done a test where I let the PC run until the battery runs out. My initial test shows I can run the PC for 30mins before it cuts out. After a few more test I realised the PC had already locked after 20mins of running. I play a DVD, surf the net and so on and this reduce the running time even further.
    The point Im making is reliabilty and stability still need to be taken into consideration...and not just it runs and so it runs attitude.

    The reason why manufacturer always recommend designers to stick within the operating spec.

    Im sure I have already said once before that the PSU spec must be within +-5% tolerance. Even though you can go outside this spec and have a PC running happily but it doesnt mean this out of spec voltage can run on another batch of PCs.

    Test on different temperature, humidity and so on may crash the machine.



    EDIT :

    The post is not for you justICE, it was for poeple who find it really difficult to understand the reason for being within the operating spec

  6. #56
    FLAC
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    So is your tank circuit intended just for surviving the crank or also for allowing you to run the PC off a 2ndary battery for a while? You seem to have spent a lot of time optimizing the circuit for the latter but in a lot of other posts seem to be saying it's only the former.

    (I apologize if I'm misrepresenting your postings - there's been an awful lot of them ).

    The reason I'm asking is that the intended use of the circuit dictates a lot of the answers to various choices for how the circuit is implemented and behaves.

    I thought it was only 3 minutes @ 2.7A output with your 0.8Ah battery?
    Progress: 80% - Permanent install left.
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    Vista, Bu-535 GPS, RoadRunner, MPT2006.

  7. #57
    Raw Wave
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    So is your tank circuit intended just for surviving the crank
    Purely for surviving a crank, I simply dont have anymore space for a bigger battery.

    I apologize if I'm misrepresenting your postings - there's been an awful lot of them
    Accepted


    I thought it was only 3 minutes @ 2.7A output with your 0.8Ah battery?
    It was the test I done on the bigger battery, I gone smaller because theres no need for a bulky one....it is a personal choice in my opinion.


    The reason I'm asking is that the intended use of the circuit dictates a lot of the answers to various choices for how the circuit is implemented and behaves.
    Yup, depend on what you want to do, then you have a slighlty different setup.

  8. #58
    Raw Wave
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    To be honest, I cant see myself instaling 50Ah battery

    Some poeple can...its still not wrong to do so. I was more worried about the cost, weight and the bulk.

  9. #59
    FLAC
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    Quote Originally Posted by Ricky327
    To be honest, I cant see myself instaling 50Ah battery

    Some poeple can...its still not wrong to do so. I was more worried about the cost, weight and the bulk.
    Granted. I was hoping a 7.2Ah (which I can easily fit inside the dash) would work for me. I now suspect (thanks to your education ) that the ~12A current requirements of my mATX system may mean I need a bigger battery to avoid too big a voltage drop. I can probably get 2 in easily enough (in parallel) and maybe even four if I remove the small cubbyhole and cover up the DIN slot it occupies. But then that's $40 ($10 each) which defeats the point of trying to do it all on the cheap myself .

    Still trying to come up with a cheap regulation system since I'm not using a VIA it matters a lot more than I'd realized because my system actually uses the 12V. I'm wondering if there's any way to produce various voltage drops from the input using diodes and then have a cheap pic choose the one to hook to the PC based on how close it is to 12V and switch dynamically as voltages change.

    I found some suitable voltage regulators but they suffer from the usual - needs ~1.5V over the desired voltage. I'm thinking maybe it's possible to build a circuit that uses the output of one of those if it's managed to produce the 12V (i.e. input was ~13.5V or more) or feeds directly if it hasn't (input less than ~13.0V), maybe with a diode or drop as needed.
    Progress: 80% - Permanent install left.
    Motion LS800 Tablet PC and dock.
    Vista, Bu-535 GPS, RoadRunner, MPT2006.

  10. #60
    FLAC
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    Update:

    The max current draw under load is only 7A which drops the battery voltage from 12.85V unloaded to 11.8V. It ran fine running Prime 95 for about 5 minutes before I got bored. The voltage had very slowly dropped to 11.55V by then. So this battery is coping just perfectly!
    Progress: 80% - Permanent install left.
    Motion LS800 Tablet PC and dock.
    Vista, Bu-535 GPS, RoadRunner, MPT2006.

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