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Voltage regulator question

Discussion in 'General Electronics Discussion' started by NMNeil, Apr 24, 2016.

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  1. NMNeil

    NMNeil

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    Oct 3, 2014
    My project is to be used on an old 1949 Ford tractor. Incredible performance of 0-60 in about 3 weeks:D
    The unfortunate thing is the ignition system is so noisy that a radio will pick up the interference from about 5 yards away, but I want to use a micro-controller!
    I read the National Semiconductor voltage regulator handbook from 1980 which gives an automotive tolerant circuit using an LM2930, which is now obsolete as is a rarity. But looking at substitute LDO regulator IC's it seems to be far cheaper to use a $1 DC to DC EBay convertor that build the circuit from scratch.
    So here's what I'm thinking. Keep the DC to DC convertor in a separate enclosure from the microcontroller, add extra caps before and after the convertor, with a 36 volt TVS as a precaution. Set it to output 8 volts and put a regular 7805, with the datasheet suggested caps, on the shielded microcontroller board.
    Will this be enough to keep the microcontroller happy and not constantly resetting?
     
  2. hevans1944

    hevans1944 Hop - AC8NS

    4,543
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    Jun 21, 2012
    Are you kidding? EMI-proof the ignition radiation from a 1949 Ford tractor? You would have to enclose the whole tractor inside a Faraday cage and surround that with a mu-metal shield. Or maybe instead do the same thing with your electronics. Hard to say what will work down on the farm, but your approach is worth a shot...
     
    duke37 likes this.
  3. duke37

    duke37

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    Jan 9, 2011
    You have not said where the interference comes from. The Fordson tractors of this age that I have seen have no electrics except the magneto.
    The plug leads should be changed to resistive cable and preferably made as a coax cable, this was done on WW2 aircraft with special screened plugs.
     
    hevans1944 likes this.
  4. NMNeil

    NMNeil

    109
    10
    Oct 3, 2014
    Front mounted distributor with solid core plug wires.
    I intend to change them for carbon wires and add resistor spark plugs to try and help.
     
    hevans1944 likes this.
  5. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    And do shield your electroinics. I prefer die-cast aluminum Bud boxes with covers secured with machine screws (actually they provide self-tapping machine screws IIRC). These (or clones) are also available with a woven wire gasket in the cover, but it probably isn't necessary to go that far. Problems, if they occur, will be related to holes you drill in the box to get power and signals in as well as signals out. Advisable to connect the project box with a braided ground strap to the engine and/or chassis of the tractor, and use an LC filter in the battery lead if powering from the starter battery.
     
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