Help protecting digital equipment

Discussion in 'Homework Help' started by Scott Manning, Feb 12, 2015.

  1. Scott Manning

    Thread Starter New Member

    Feb 12, 2015
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    0
    Hello all. I am new here so apologies in advance for anything stupid I WILL say.

    I am in need of advice with a modification I am in the process of carrying out to my digital slot car track. Basically I am building a change over switch so the track can run in digital and analog modes (no together). In digital mode the left rail is positive and right rail is negative. In analog the polarity is reversed. The digital system is controlled by what is known as a black box which is where power is distributed from. Forming part of the digital experience are lane changers, position towers, lap counters etc, all of which connect to the positive and negative rails of one of the tracks with 2 wires only. I assume that they receive digital signals down the power wires directly from the black box. The switching of the lanes from digital to analog and the isolation of the black box is no issue and already complete. What I am struggling with is protecting all the other digital equipment from damage as a result of reverse polarity in analog mode. Everyone who have posted information about modifying their own tracks say the have gone to the trouble of interrupting power to the digital accessories via individual switches or physical disconnection but I suspect their might be a smarter way. My thought process thus far is I might be able to implement reverse polarity protection by using diodes of P FETs at each piece if digital equipment. My theory is that when in digital mode (correct polarity for digital accessories) everything will work as originally designed - when I switch the system to analog mode and reverse the polarity the diodes or FETs will prevent reverse polarity flowing through digital devices effectively isolating them from the track rails. I am sure most people who read this thread will be much more capable them myself in this field so what do you think? I would really appreciate some advice.
    Kind Regards.... Scott
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    I think something like what you have in mind is workable. The devils are in the details, so we would need more information to figure out what configuration is most likely to work for you.
     
    Dr.killjoy likes this.
  3. Scott Manning

    Thread Starter New Member

    Feb 12, 2015
    28
    0
    Thank you so much for your reply. If you can let me know what would help I will gather the info. Is that workable?
     
  4. Scott Manning

    Thread Starter New Member

    Feb 12, 2015
    28
    0
    So I went ahead and carried out the modification where I created a switching ability between digital and analog (using two car digital chips to provide power to the track rails in analog mode) and I placed diodes in the positive feed wires to every piece of digital equipment. Works like a charm, all digital equipment is electrically isolated in analog mode.
    Another person in my club asked me to do this to his track but added he would like to to be able to operate the analog mode track in both polarities to enable reverse track racing. If the varying analog power being supplied to the rails is the correct polarity is it likely to cause damage to any of the digital equipment? Beside a switch is there any way to isolate the digital equipment when in analog mode regardless of polarity?
     
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