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Thread: I just don't get it...

  1. #1
    Low Bitrate dapepster's Avatar
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    Unhappy I just don't get it...

    I recently revised my MP3 player in my car to this motherboard (all-in-one), and this power supply. I have also moved the entire setup from the front part of the trunk area to under the driver's seat (since the whole thing is small enough).

    Okay, now the problem: if the engine is not running and the PSU is running just off the battery (~12 VDC), the system runs fine. I can start the machine and boot it to Win98SE and it'll play DVDs and MP3s perfectly. HOWEVER, if the engine IS running (making the alternator produce between ~13.5-~14.5 VDC), I can't start it up at all. I can push the start jumper button and the screen will just flash white for a split second (literally), and turn the system off. If I press it again afterwords, it won't try to turn the system on again, as if the power supply has hit it's max voltage input (which on this supply is 15V).

    I've tried using 12V and 13V 1W zener diodes between the PSU +12V wire and ground, but that doesn't seem to do anything. I had the power supply replaced for free because I thought that was the problem, but the new one is doing the same thing the old one was doing. I've tried to purchase a 1N6273A zener diode for a higher power rating, but they only sell them in bulk pakages of 500.

    As far as ground points, I started with it next to one of the rear seatbolts (which I found out later isn't a good ground), then I created one under the center console where there is a metal cover over the e-brake handle, and I tried to use my old ground point under the back seat cushion. NONE of these have worked. Some other info I have on this system is that it is fused from the positive battery post under the hood and fused to 10A, and the system normally only draws 8-9A.

    What can I do to keep this thing alive when the engine is running???


  2. #2
    FLAC
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    Dapepster,

    Have you tried running your ground wire all the way back to the negative terminal on your battery? This may help.

    Also, an input voltage of 15V max is a bit on the edge for a car PSU. This may be part of the problem. I have seen spikes of 16-18V under various conditions. I wouldn't recommend the 1N6273A since it's breakdown voltage is 12V. You'll probably burn it out quickly if you're using it on the input to the PSU since there's nothing to limit the current into it. If you are trying to add some sort of overvoltage protection on the input, you need something that limits around 16-18V. However, you can't use this as a "pre-regulator" to regulate your regulator..... . These "mosorb" type zeners are designed to take very large, very SHORT transients. They are not designed to be used as a voltage regulator for high power dissipation.

    Hope this help! Good luck!
    MikeH

  3. #3
    Constant Bitrate
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    You could also try a combination of a Capacitor In parrallel and an Inductor in series on the supply input to see if you can clean it up. A large rectifier in series with the supply will drop the voltage about .6 volts, and that might work as well. You will need one that is rated at 15 Amps or so.

    Good Luck
    Walter Farmer
    http://www.safossils.com/mp3car.html

  4. #4
    Constant Bitrate CHUPACABRA's Avatar
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    Try regulating the power to keep it at 12v.Or use a incar adaptor for a tablet pc or laptop at 12v

  5. #5
    Maximum Bitrate starfox's Avatar
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    You could also try to build a circuit based around a high current low dropout voltage regulator, like national's LM1084, to make sure that you don't get more than 12V in to your DC-DC PSU.

  6. #6
    FLAC
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    Chupa...most laptop regulators are 60W or less. He's got a PW200 which is supposed to supply 16A at max output. However, I read on another thread that 70% of this is un-regulated +12v (ie....a wire from input to output).

    Starfox..... the LM1084 is only good for 5A. This will work if he's willing to limit his power consumption to less than 60Watts.

    I find it odd that his regulator nees a regulator....
    MikeH

  7. #7
    Low Bitrate dapepster's Avatar
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    Angry

    Okay, I guess my electronics knowledge doesn't mean anything, because it's still doing it. I've redone the mounts on the case for the MB with rubber spacers so there's no chance of grounding anything on the MB. I've also wired the ground to the battery, the old spot I had under the back seat cushion, and the spot I created yesterday near the e-brake handle. I even tried all three tied to ground at once!

    All I can assume is it's the motherboard that's screwed up.

  8. #8
    Low Bitrate dapepster's Avatar
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    Lightbulb

    I'm just now discovering this: it'll stay alive with the engine running UNTIL:

    1) the engine revs to 1000 RPM, or
    2) the car gets to 15 mph and the speed-sensitive door-locks engage

    Now after monitoring my multimeter, I'm thinking it is definitely the power supply having a max input of 15V, because my old TOP power supply had a 9-18V range, versus this 10.5-15V. And I NEVER had this problem with that.

    Time to purchase an Opus....and wait....

  9. #9
    Variable Bitrate Pokey's Avatar
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    I would say that your converter won't run if its supply is dirty, as in high ac ripple on the 12V. The 12V-14V coming from an alternator is not a pure DC volts, your converter might see this as dirty and shuts down. UPS's do the same thing with dirty AC.

    Try running a bridge before the converter.
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  10. #10
    Low Bitrate dapepster's Avatar
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    Question

    Quote Originally Posted by Pokey
    Try running a bridge before the converter.
    What convertor..? This is a DC-DC psu...

    Also, what's a "bridge" (I feel stupid )?

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