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  • operating frequency

    i am interseted in building a car computer. th only problem i am having is powering the computer. i am way to chp to buy a dc-dc converter or an inverter for that matter, but i do hav some big transformers lying around. what i am asking is is if th power supplies in computers can run on different frquncys than 60 hz, or on pulsed dc?

    another qustion is, i hav a 486 i was gonna us for the comp and i wonder if will support large drivs lik in the gigabyte range

  • #2
    Originally posted by cirvin
    i am interseted in building a car computer. th only problem i am having is powering the computer. i am way to chp to buy a dc-dc converter or an inverter for that matter, but i do hav some big transformers lying around. what i am asking is is if th power supplies in computers can run on different frquncys than 60 hz, or on pulsed dc?

    another qustion is, i hav a 486 i was gonna us for the comp and i wonder if will support large drivs lik in the gigabyte range
    Most computer pwr supplies will work with from either 50hz or 60hz AC....pulsed DC will NOT work. DC-DC convertors are the optimal choice, but if you are on a budget (everyone is to some extent) I would recommend a AC to DC convertor...you probably get one for $35 - $50

    I wouldn't recommend using a 486 in your car it's so slow, outdated and doesn't use an ATX power supply look at what you can get for $50

    http://cgi.ebay.com/ws/eBayISAPI.dll...category=51097
    My Celica Carputer Install

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    • #3
      A PC power supply can be modified to run from DC input. In fact on of the first parts at the input is a rectifier.
      This is kind of useless though as this DC is ~300V.

      white bream
      working on a trilogy: CARGO - UNIGO - MERGO
      CARGO = the Car Computer
      Intel Celeron M, [P]SDC, uBlox GPS, GPRS, WLAN, Silabs FM, RDS, TMC,
      Dual-audio, Onecable TFT, Microsize: 45 x 108 x 168mm (1.8 x 4.3 x 6.6")

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      • #4
        Interestingly enough, I been thinking if its possible to modify the input parts of the standard 240V ATX PSU such that it can work with 12V.

        I dont have a spare PSU right now, but I think it may be worth a look

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        • #5
          Interesting theory.

          The first thing the AC power goes through is a step down transformer. If it is a one winding step down, then you could supply that voltage to the rest of the power supply for the rest of the regulation.

          If it is a multiwind step down, then you will have to supply multiple voltages to the rest of the regulation.

          (if you do all that work to supply voltages...what do you need the psu for)

          So in theory it might be possible to modify a PSU...but most likely not.
          current projects

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          • #6
            so it can't run on like 400 hz? watif i use a 555 timer and ti the output and trigger to an op amp, having the trigger in the inverting side and the out on the non inverting sid, then use that to driv a transformer through a 2n3055?

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            • #7
              Originally posted by DodgeCummins
              The first thing the AC power goes through is a step down transformer.
              I haven't seen a modern PC power supply that does this. Most that I have seen (as henkbliek said) put the AC through a rectifier to convert it to high voltage DC. Then it gets switched through the primary of the transformer, with the regulator controlling the switching transistors.


              Rob
              Old Systems retired due to new car
              New system at design/prototype stage on BeagleBoard.

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              • #8
                Very interesting reading...in the old days switching powersupplies were not well received.

                http://www.howstuffworks.com/power-supply.htm
                http://www.epanorama.net/links/psu_computer.html

                I stand corrected...

                So where does one get 120vdc...(US current)
                current projects

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                • #9
                  if they rectifiy it before using it, then it should run at any frequency , or even at dc right?

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                  • #10
                    http://www.technick.net/public/code/index.php

                    Check CIRCUITS > POWER SUPPLY

                    Yup its DC at about 300V though.

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                    • #11
                      i could just eliminate the input rectifier. and run 120 dc to that. i have a 120v dc motor i could just belt to the engine. thast would probably be too dirty. wait. u meen after rectifacation, the voltage from the rectifier is 300v!?!? that would n't be much of a prob tho, just finding the right transformer

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                      • #12
                        I am not the smartest guy in the group, but if you have a US system that is designed to run off 120vac mains, then when you rectify that (diode bridge) to DC...you get 120vdc (minus a bit for heat transfer)...The European guys can play with the 250v.

                        I don't have any idea what a 120vdc motor could be used for, but if you had one, and put a load on it, (with a little rewiring)it would make a dc generator...but it would really be crappy at the job...

                        Just get one of those DC-DC power supplies.
                        current projects

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                        • #13
                          i have a 120v dc motor i could just belt to the engine.

                          Yes, that can work...but aint we going back to the inefficiency situation again?

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                          • #14
                            Originally posted by DodgeCummins
                            I am not the smartest guy in the group, but if you have a US system that is designed to run off 120vac mains, then when you rectify that (diode bridge) to DC...you get 120vdc (minus a bit for heat transfer)...The European guys can play with the 250v.
                            Nope, 1.41 times for a full wave bridge rectifier (less a little bit for voltage drop across the doides - the heat transfer you talk of). Don't forget the 120vac is an RMS reading, it peaks higher than that. Same for 250vac.

                            See here for more info about bridge rectifiers:

                            http://www.mitedu.freeserve.co.uk/Design/dcpsu.htm

                            So 250v ac turns into around 350v dc, and 120v ac turns into nearly 170v dc.


                            Rob
                            Old Systems retired due to new car
                            New system at design/prototype stage on BeagleBoard.

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                            • #15
                              so it should manage at 120 dc

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