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Thread: shutdown and regulator question..

  1. #1
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    shutdown and regulator question..

    hey all, I'm probably building an epia-based carputer in the near future, but I have a few questions.

    The system will probably be linux based - I remember reading awhile ago that if I mount the filesystem as read-only then I can turn off the system at anytime without damaging files - thus eliminating the need for a shutdown controller. Can someone confirm this?

    and secondly, I'm going to be getting a Cubid 2677 or 2688 case, which comes with an unregulated DC PSU. So I need a 12V regulator... only problem is, I don't know how to read those circuit diagrams or whatever you'd want to call them. I'm not dumb by any stretch, I just have never worked with them before. Could someone explain this diagram? I could manage to find the parts and solder them myself or whatever I'd have to do, I just don't quite understand the diagram!



    Help much appreciated!

  2. #2
    Newbie dieter's Avatar
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    You're going to need at least 12+1.5(worst case) = 13.5 volts to run this--you can forget about this regulating when the car is off. The circuit wouldn't be hard to build. You'd just need to go to digikey.com for the parts, and get a perf board from radio shack, and heavy wire. Make sure the capacitors have a high enough voltage rating or they'll explode. The capacitors also have to be installed correctly (correct polarity) or they will explode.

    You'll also need a heavy heat sink on this--bolt the regulator to a metal case, and use some thermal compound to improve contact.

    I personally wouldn't use this circuit in my car--I don't think it offers enough protection.

  3. #3
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    Originally posted by dieter
    You're going to need at least 12+1.5(worst case) = 13.5 volts to run this--you can forget about this regulating when the car is off. The circuit wouldn't be hard to build. You'd just need to go to digikey.com for the parts, and get a perf board from radio shack, and heavy wire. Make sure the capacitors have a high enough voltage rating or they'll explode. The capacitors also have to be installed correctly (correct polarity) or they will explode.

    You'll also need a heavy heat sink on this--bolt the regulator to a metal case, and use some thermal compound to improve contact.

    I personally wouldn't use this circuit in my car--I don't think it offers enough protection.
    OK well I read through the elctronics section of a robotics book I have, and now have a MUCH greater understanding of the schematics, so I think I can handle building things such as this.

    But if it wouldn't be a very good design, can you or anyone recommend one that IS good? I'd like to be able to use it with the vehicle on or off, and I MAY need to power a 14" VGA LCD screen (a Nortec 14" LCD - only $170 and I have enough room in my vehicle - not decided yet though)

  4. #4
    Newbie dieter's Avatar
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    Good power supplies are expensive. If you want it to run when the car is off (low voltage) it has to have boost circuitry in it. If you want it to withstand surges and spikes, it needs fairly elaborate filtering on the front end, and if you want decent efficiency (minimal heat), it will be a switched supply (not a so-called "linear" regulator like the circuit above which just turns excess power into heat). Add high current-handling capability and all the components must be beefed up. You get what you pay for--I'm personally holding out for the opus PS.

  5. #5
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    hmm so my best bet would be to use an inverter and live with the static (or remove my head unit and hook it straight up to the amp)? sounds like making a GOOD powersupply and/or regulator would be way too much trouble, and I definitely don't want a shoddy solution.

    Would it run with the vehicle off with an inverter though? And I wouldn't need a shutdown/boot controller since I'm using a read-only filesystem?

    Thanks.

  6. #6
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    inverter

    Well from my experience, I have very little static in my audio. the only time it will make noise is if the ground of my computer touches the frame of my car.

    As far as powering with the car off concerns, I'm using a 300w inverter, but my system only draws 60 watts. With my 200 watt subwoofer running also, I have can run the system up to about 30 minutes before the alarm on the inverter goes off. This alarm goes off supposedly when the battery gets to 11 volts, and shuts power off when the battery gets to 10volts.

    http://phillip.darktech.org/mp3box/mp3box.htm
    -Phillip

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