Need schematic for LM7805 5V regulator

Discussion in 'General Electronics Chat' started by big jim, Jun 1, 2009.

  1. big jim

    Thread Starter New Member

    May 31, 2009
    I want to save some money instead of buying the cigarette lighter adapter for my Sirius Sportster 5 car radio 12V to 5V I want the schematic for the LM7805 5V DC regulator. I should be able to get the components from Radio Shack.
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Google "7805" and get a data sheet. It will have everything you need. If your load draws much current (say over 100 ma), you will want to add a heat sink to the regulator to keep it cool.
  3. bertus


    Apr 5, 2008

    The schematic can be found in the datasheet.(attached PDF).

  4. Mike Mandaville

    Active Member

    May 27, 2009
    I smoked a lot of 2102 memory chips before I got smart and started to use that regulator.
  5. Wendy


    Mar 24, 2008
    Another approach is to buy phone charger and modify it. They are cheap because of being mass produced, and are much more efficient than a linear regulator, which can run extremely hot. This heat is hard to get rid of, and modern electronics uses different approaches to the problem. A 5V 1A load with a modern power supply will take less than ½A at the cigarette ligher, since it is being converted and not regulated. That same 1A with a linear regulator will be around 7W, which can generate enough heat to melt plastic.

    I have a project on the back burner to do something similar, but it's not ready for prime time yet.
  6. radiohead

    Active Member

    May 28, 2009
    I've built over 50 of these since January. Obtain an LM7805, connect a 1uF electrolytic 50V between the input pin and the ground (observing polarity), and connect a .1uF between the output positive and ground pin. There you have it, a +5V regulator that can accept between 6-35VDC with a 5VDC output with a rating of 1 ampere. One word of caution, if you are converting voltages above 9VDC, use a heat sink with heat sink compound. The reason for this is to aid in the transfer of heat generated from the device to the heat sink so the 7805 will last longer.