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Thread: What capacitors can you use for a tank circuit?

  1. #1
    Maximum Bitrate
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    What capacitors can you use for a tank circuit?

    I went down to my local electronics shop and I found many different capacitors available, but I'm no expert on exactly what I can use and what type of diode I need to go with it.

    Here's what I found:

    (new) 10,000uF 35V $4
    (oldschool) 56000uF 15V $1
    (oldschool) 79000uF 15V $2

    now getting the diode is a different thing, they didn't carry anything nearly that large (60A forward current, max they had was 2A).

    The question is, can I use these oldschool caps (big blue suckers)? They're obviously used, date on them is 5/81. I would imagine that they've probably degraded in capacity, but are they still worthwhile to try out? Would I need a huge diode for that as well? 15V should be fine, right, because the max voltage on the line is 14.2V (on my car)... it might spike higher than that for very very short periods of time, but it's steady at 14.2V

    Anyone know what I should do?
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

  2. #2
    Constant Bitrate
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    What exactly are you trying to accomplish?
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  3. #3
    Maximum Bitrate starfox's Avatar
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    I don't think 15V will be fine, as you said it spikes, and spikes tend to make capacitors get warm, and later explode... leaving bits of brown stuff everywhere and a very strange smell.

    Also, are you sure you want to build one of these? Diode alone will get pretty warm, and you'll drop at least 0.7V due to it.... Might want to try and use a high current bridge instead (something you can heatsink at least)..?

  4. #4
    Maximum Bitrate
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    Well the idea of the tank circuit is to provide power to your carputer/stereo/whatever while the car is cranking.

    You can get diodes with 0.4V forward voltage bias, but you'd be hard pressed to get anything smaller than that.
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

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