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Thread: Why are DC-DC power supplied so expensive?

  1. #21
    Low Bitrate
    Join Date
    Jul 1999
    Location
    Brisbane, Australia
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    105
    Yep.. fine.. if you can build one for that price then it is a much better alternative.. I'll swap my inverter for your DC-DC power supply along with 3 cartons of beer anyday.. although the beer is main concern

  2. #22
    Newbie
    Join Date
    Oct 1999
    Location
    Waukesha, WI, USA
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    1
    While were on the topic of dc-dc power converters. Does anyone know of a website that sells dc-dc'c with working -5v? Also, if anyone has any websites with affordable inverters, could you please list em. Thanks in advance!

  3. #23
    Variable Bitrate
    Join Date
    Aug 1999
    Location
    Yorba Linda, CA
    Posts
    323
    How many of you can keep your car MP3 player running WHILE starting the car? I'm just curious because when I used to use an inverter, the voltage would sag too low and the computer would hang or reboot.

    It was kind of a pain to shut the system off, start the car, and then boot it up again after the engine was running if I was sitting in the car with the engine off listening to my MP3s waiting to pick someone up, for instance.

    Obviously this doesn't apply if you have the computer tied to the ignition switch Just curious...



    --Jason
    http://jump.to/m2pc
    Jason Johnson
    Yorba Linda, California
    http://www.m2pc.com

    MPC Phase IV - *** PENDING ***

  4. #24
    Constant Bitrate
    Join Date
    Oct 1999
    Location
    CA, USA
    Posts
    118
    To address just this issue, I made a board for a friend's powermac based MP3 player. It monitors the car's ACC line and only activates the onboard relay if the ACC is on solid for 5 seconds. This is to help prevent his mac from booting during cranking. The relay feeds the computer/inverter.

    Once the relay is activated, a 'powergood' signal is sent to the mac's serial port. If the ACC line goes dead for 8 continuous seconds, a "powerfail' signal is sent, and after 30 more seconds, the relay is turned off. This way using UPS software, his Mac will shut down properly. The 8 seconds delay before sending the powerfail signal is to prevent his MAC from turning off if he stalls his car and needs to restart the engine.

    I've since tried the same board with APC's powerchute software on NT and Windows95 and it works well! Another guy is using my same board for his Linux based MP3 player, but he isn't currently using the Powergood/fail status line, just the smart relay controller portion.
    Dave

  5. #25
    Low Bitrate
    Join Date
    Sep 1999
    Location
    Australia
    Posts
    99
    I know this is getting right off the subject but....jjohnson, something that has always worried me (not enough to look into though) is, could there be any problems with back EMF from the starter motor when leaving audio stuff on during cranking? next,... Probedude_2000, Ive been trying to get hold of that powerchute software for ages, I saw a site back when I was building my player where someone used the powerchute software and a simulated low battery input to shut down their player. Do you know where I can get the powerchute software?

  6. #26
    Variable Bitrate
    Join Date
    Aug 1999
    Location
    Yorba Linda, CA
    Posts
    323
    I never thought about back EMF... I do know that some car devices (cell phone chargers and CD player adapters) say not to have them on while starting the car. I'm not sure if this is because of the voltage sag that occurs or if it's because of back EMF. Hehe, you could always wire a transient suppressor (MOV) across the coil on the starter, or even a diode to short back EMF spikes to ground.

    Hmm... another feature to add to my car!


    --Jason
    http://jump.to/m2pc
    Jason Johnson
    Yorba Linda, California
    http://www.m2pc.com

    MPC Phase IV - *** PENDING ***

  7. #27
    Newbie
    Join Date
    Sep 1999
    Location
    Lawrence, KS USA
    Posts
    46
    I'm using the ACE-865, the one you can get from Arise. Starting the car doesn't kill the computer.

    LowLife

  8. #28
    Newbie
    Join Date
    Sep 1999
    Location
    Lawrence, KS USA
    Posts
    46
    Oh, and for all those that think its convinent to have a AC power supply and an inverter in their car so they can bring it into the house and work on it easy...

    All I do is plug the 12v out from an AC power supply (that is sitting behind the computer desk in my room) straight into the 12v input on my DC-DC Mobile. Works great and doesn't take up hoards of space.

  9. #29
    Constant Bitrate
    Join Date
    Oct 1999
    Location
    CA, USA
    Posts
    118
    I got the powerchute software from the APC website itself about 3 weeks ago.

    Did you try them?

    If anyone is interested in looking at what my powerup/powerdown board, go here
    http://www.dschmidt.com/autooff.html

    Dave

  10. #30
    Variable Bitrate
    Join Date
    Aug 1999
    Location
    Yorba Linda, CA
    Posts
    323
    I have an old Camaro (1970) with a big V-8 engine. While cranking the battery voltage sags below 9V That would explain why my computer would go crazy if I left it on while starting the car. But a custom electrical system and DC-DC will solve this

    I'll be using a separate battery for the computer and onboard electronics, so I won't have to worry about this kind of thing anymore.

    --Jason
    http://jump.to/m2pc
    Jason Johnson
    Yorba Linda, California
    http://www.m2pc.com

    MPC Phase IV - *** PENDING ***

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