Using electronics in the auto

Discussion in 'The Projects Forum' started by tracecom, Oct 7, 2012.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    For some time, I have been using a small audio amp with my MP3 player in the truck, but I have been using alkaline cells for power. Now, I would like to power the amp from the auto power supply. The amp circuit is rated for up to 18V. Do I need to take some precautions to protect the amp from noise and load dumps, and if so, what? Thanks.
     
    Last edited: Oct 7, 2012
  2. cork_ie

    Member

    Oct 8, 2011
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    If we had the instruction booklet or datasheet for the AMP it would be a great help.
    Do you have a Model Number?
     
  3. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    The amp that I have been using is based on the LM386 and is homebuilt. The schematic is attached.

    However, I am thinking about upgrading to a version of the TDA7297 amp in the second schematic.
     
  4. cork_ie

    Member

    Oct 8, 2011
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    I had a look at the datasheet and there are no specific recommendations.
    I see there are different versions most with an absolute max voltage of 15V and the LM386N-4 with 22V

    If it were my amp I would simply drop the input voltage on the 12V+ side 0.7 V through a 3A diode (3A to future proof for higher loads) or better still 1.4V with two in series. This will keep you well clear of the 15Volt limit
    Then a simple lowpass filter made from a suitable 100μH series inductor and a 0.22μF capacitor should filter out any line-born noise.

    If you still get noise you could try increasing the capacitor value
     
  5. wayneh

    Expert

    Sep 9, 2010
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    A lot of folks use a 7812 regulator to smooth things out. That just leaves the big stuff to worry about, spikes and whatnot. A 15v zener on the input maybe?

    If you want to use valuable electronics, I might look more into the problem but in my limited experience, things seem to survive just fine without extraordinary measures.
     
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