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Thread: In Car PC..

  1. #1
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    In Car PC..

    Hey

    I don't know if this is the right place to post a subject like this but i have tried loads of places with no joy. Right the thing is i have just bought a computer for my car and will be installing it next week which is here.

    http://www.scan.co.uk/Products/Produ...roductID=91886

    I have everything i need e.g. screen (Kenwood KVT-M700) ect all i wanted to know was about the powering side of things.

    My friend has said to me i have two options.

    1) Use a mains inverter. This creates a 240vac feed from the battery which you plug the mini-itx's external mains adaptor in to.
    This is a waste of energy though - power is lost in both conversions. Cheap inverters also work on a modified sine-wave so output
    a lot of noise on the supply which can cause buzzing through your speakers and interference on the screen.

    2) Buy a voltage regulator. This will increase or decrease the voltage as necessary - it sits in between the car battery and the pc's
    12v input. This is the best option. i have the regulator inside the pc case. The pc will run for 8 hours without the engine on!

    Now i am not to clued up on this sort of things but the second option seems to be better to me. But have not got a clue what i
    voltage regulator is/does and where to get one from. Also the pc don't run off a 12v so i don't know what to do. If you can shed any light on this matter that would be great.

    Cheers
    RealM

  2. #2
    Administrator Moby-Dick's Avatar
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    I've seen in car PC's run off an inverter , and they seem to be pretty good.

    Why not run a small UPS off the inverter , and run the PC from the UPS - that should smooth the signal to it.

    I was going to do an in car PC , but my head unit already plays MP3's and my PDA will play anythign else ( unless I decide to go with an xbox based system. )
    my Virtualisation Blog http://jfvi.co.uk Virtualisation Podcast http://vsoup.net

  3. #3
    PMM
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    Lots of stuff available but you need to go looking around as some of it is
    OTT in price other stuff rightly priced.

    Do Google searches for DC-DC ATX PSU

    For example...
    https://linitx.com/index.php?cPath=2...c6d62b7d85c14b

    Various stuff about just a matter of defining what your Power Requirements
    are and picking the nearest thing to suit.

    /edit.. + http://www.kustompcs.co.uk/acatalog/info_1730.html

    /edit2..+ http://www.watt-power.co.uk/page7.html though they don't quote prices.
    Last edited by PMM; 17-08-2004 at 08:40 PM.

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    Ok guys, im Realms brother, it seems that some of you are confusing the 12v VIA M100 varients with this P4 19v system.

    Anyhow i will re ask the same question.

    Now ive searched around these forums for an answer and have tried various other sources but i am still in a pickle.
    So here is yet another newbie power question, which i hope some don't mind replying too.

    Ok i am wanting to put my ZPC Iwill pc inside my car. I am having trouble trying to get a dc-dc convertor as the input on my ZPC is 19v.
    Now i know a lot of you have been using the VIA M1000 based stuff so power input to them is 12v so no worries for you there but i am stuck where to go and what to do.

    Here are the specs on my ZPC system:



    90W power adapter
    110V - 240V, full range AC input
    DC 19V (6.32A) output from power adapter

    Specs
    P4 2.8 533fsb
    512meg DDR 333
    40GB HD 8 meg cache 2.5in 5400RPM
    Intel Extreme graphics
    DVD/CDRW drive
    Win XP

    Now what i need is a feed from the 12v car battery to go into something that converts this feed to 19v and have the right connectors that my ZPC uses. It has a kind of 4 pin ps2 connector on, the same size as the mouse/keyboard port on a pc but with 4 larger pins only.
    It was also suggested that i take out my ZPC internal power supply and use another item that will work with the setup i need but it is not the same as other itx/via power supplies that have some outputs for stuff.
    If you look at the picture above then you may notice the power supply item in the ZPC uses a slot kinda like an IDE connector (same size anyhow) and there are NO other outputs/inputs on this power supply or other connectors.
    Also i am wanting to regulate the power and have it on a switch like most of the VIA users here have been doing with the Ituner ITPS Car Power Regulator so when i turn on the car it powers on pc and when i switch car ignition off it waits about 5 seconds then shuts down pc. Basically a switching unit that has 2 feeds, 1 to the battery and another to the ignition but one that will work with my ZPC.
    Would the ituner work for my ZPC though, i think not as its only a 12v feed so can anyone clear this question up for me please?

    Now i dont want to go down the invertor route as that is a waste of power as the unit only needs 19v DC and also i don't want to have to wait until my car is switched on because of an invertor with the power going to the starter motor first and turning pc on and off all the time.

    Here is a link to the official website with more info.

    http://www.iwillusa.com/products/Pro...il.asp?vID=179

    However i have found this dc-dc convertor.


    http://www.watt-power.co.uk/page7.html

    Auto Adapters for use with WPPS80 and WPPS80A DC-DC Converters. Simple Power to Power DC-DC converters. Cigar Lighter input plug, output plug 2.5mm Jack centre positive. This is a quality unit, intended for in car fixed installation.
    WPPS12019 with 11-16vDC input (12v Systems) , output 19vDC at 6.3 Amps

    Now this unit seems fine for my ZPC but i may have to cut the connector on my old PSU unit that i have in the house to make sure the end that is going from this dc-dc convertor will fit my ZPC.

    Anyone know from looking at the specs here that it will be fine. Ive been told a yes but would love to hear some more advice.

    Also how would i go about getting a switching unit so that i could have 2 feeds, 1 to ignition and the other to permanent battery. I really want to have an auto shutdown and not an instant off when ignition turned off or engine starting.
    Also how can i have the ZPC boot up when ignition on? Will i need some sort of wiring to the power on button on my ZPC?

    Help appreciated again thanks...

  5. #5
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    Any help guys? I know its a long winded thread but im short of becoming bald with frustration over all of this...
    Wish i had a penny for the ammounts of time my head hit a brick wall...

    Any help is help certainly needed.

    Cheers again.

  6. #6
    Senior Member SilentDeath's Avatar
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    The standard power supply for a pc includes voltages of: 3.3v, 5v, 12v; and -5v and -12v which are optional (only needed on systems using parrelell port and or seirel ports for certain uses).

    Now that mobo seems to use a non-standard psu, in otherwords they have substituted the normal ATX standard for a simple 19v 7A regulator.

    For the electronics side of things please post in bit-tech.net electronics forums, they know this kind of stuff well...

    You basicly have three options. The mobo you are using will need to convert the 19v down to a useable voltage - hard disks need 5v and 12v, and most mobo components need 3.3v and 5v. Cpu needs ~1.6v, ram needs 2.5v etc... - on normal mobos these compnents will be fed by regulators. If you probe around on the mobo, you will likley find the points where these conversions happen, and then you will be able to by-pass the built in 19v->other voltage conversions -which should improve efficency.
    This way you can run it all from simple linear/SMPS/PWM regulators straight from the car battery without any step-up conversions.

    another option is to stick two small lead-acid 12v batterys in your boot, in series giving you 24v of potential. Charge them up by mains power before connecting them to the car, then you can connect them to the car battery in order to keep them charged. Note that If you have them connected to the car battery in order to keep them charged, then you cant use them in parerlell or it will short them. However You could use a simple, commercially available 12v -> 24v charger. You could infact use a single 24v battery (which do exist, trucks use them iirc). This gives you lots of options. You could even replace your normal battery with a truck one, and then use 12v regulators for the rest of the car... (but then you cnat have the battery charged by the cara alternator.. so forget that...)

    Your mobo will probably only convert this 19v downwards, and not use any of it at the 19v, this would make it safe to directly feed 24v to it. If it doesnt however, some parts might go bang!
    With this method you could also use a 19v regulator, which would most likley have to be of the variable kind - lm317t would be adequate if the current was lower, I cant remember the names of any 10A variable regulators atm.

    For regulation, you have to work out if linear or SM will be more efficent. With linear, ALL the not needed voltage is wasted as heat. This means if you needed 19v from 24v at 7A, then 5v x 7A = 35w will be wasted as heat, and so require a decent heatsink.
    Switched mode regulation is about 80-90% effiecent if done properly, so is good for when there is large differences between supply and required voltage. Will 20% of 24v at 7A be more than 35w?
    24v * 7A = 168w
    168w - 35w = 133w, that is what SM will have to beat in order to be more efficent.
    Assuming 80% efficency, SM will waste 33.6w, so yes more effiecnt, but not really by a noticable margin. Linear gives better, smoother power, so I would go with that, over a SM design.

    A LM338T (or LM338K) is a linear regulator rated to 5A. You can use two in parrell (with diodes to stop back flow. Outputs would have to be equal for it to work properly, but they are adjustable so wouldnt be too hard...). Another way is to use a power transistor to follow the voltage and supply the other 5A, however Ive never tryed that, but I know its possible, so ask someone if thats good idea..

    It is quite easy to keep the thing on after ignition is turned off, using a simple transtor or relay, work out how you will power it and this can be thought about after
    Last edited by SilentDeath; 21-08-2004 at 11:45 PM.

  7. #7
    Nox
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    • Nox's system
      • Motherboard:
      • Yes
      • CPU:
      • Yes
      • Memory:
      • Yes
      • Storage:
      • Yes
      • Graphics card(s):
      • Yes
      • PSU:
      • Yes
      • Case:
      • Yes
      • Monitor(s):
      • Yes
      • Internet:
      • Yes
    there is another option, sort of, its an add on primarily for land rovers and other offroad 4x4's that allow a second battery to be added for use only by the aux components, winches, extra lights etc this is kept charged by the alternator like the regular battery, but only when the regular one is fully charged.

    i was considering something along the lines of a in car pc, but have and xda 2 now instead.

    Nox

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    Dont know if youve thought of this (or seen it), but mini itx is the way to go, im a closet car geek (got me a sideways 200SX) and ive seen guys do serious installs on the ITX platform, even going so far as a wireless lan, http://www.mini-itx.com/store/ is a good place to start, hang on a min, http://www.sxoc.com/vbb/showthread.p...light=carputer , might give you a good idea. You can definatley get a specialesed converter for power. If you want some more links PM me.

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