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Voltage Regulator Constant Heat

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  • Voltage Regulator Constant Heat

    I have this 7805 voltage regulator:
    http://www.radioshack.com/product.as...%5Fid=276-1770

    I put a piece of aluminum about 2"x2" on the voltage regulator to act as a heatsink.

    When my V in (7.5V) and my ground are connected, the voltage regulator produces heat (temperature at least 104F / 40C) , even when V out is not connected.

    When V out is connected, it produces slightly more heat.

    Is it normal to see the voltage regulator producing heat even if when it's not outputing any current?

    Is it safe to put this in the eyeglass compartmet of my car?

  • #2
    bump

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    • #3
      Is the tempurature you stated the heatsink temp or the regulator temp? If that's the regulator temp then you should be ok. The regulator is rated up to 125C. I don't recall them generating any heat without a load on it but 40C is nothing to worry about. Just make sure everything is connected correctly. Left to right with pins facing down: 1-Input, 2-GND and 3-Output. The heatsink should have continuity with the center ground pin and should not be touching any of the pins. As long as the temp with your full load on it is where you said it is, you should be fine mounting it in your sunglass compartment. Just make sure you mount it so that the heatsink and regulator is not touching any plastic or fabric. Leave an air pocket around it so the heatsink will work effectively. If you have metal in there you could use it as an addition heatsink as well.
      Rick S.

      XP Pro SP2, Soyo P4RC350 MB, Nvidia FX5200, 320W PS, Inverter & uSDC20D, 2.4GHz CeleronD320, 512MB DDR, 30GB 3.5", Pioneer 106s Slot DVD, Linksys WMP54G WiFi, Lilliput 7" & 4" TFT LCD, Zippy EL610 Keyboard, Touchpad, Garmin GPS V

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      • #4
        strohmrs is correct, but mine doesnt put off any heat when it has no load.
        肚子笑痛了
        S60 Install

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        • #5
          If the temp is 40C at the heatsink without a load then he should get a new one. If the regulator has ever been hooked up wrong or has been run very hot or at a high load then it should be replaced. As I said earlier, I don't remember them putting off any heat without a load and with only 7.5V going in there's only about 0.5-1.0V being dissipated as heat. Couldn't hurt to get a new one.
          Rick S.

          XP Pro SP2, Soyo P4RC350 MB, Nvidia FX5200, 320W PS, Inverter & uSDC20D, 2.4GHz CeleronD320, 512MB DDR, 30GB 3.5", Pioneer 106s Slot DVD, Linksys WMP54G WiFi, Lilliput 7" & 4" TFT LCD, Zippy EL610 Keyboard, Touchpad, Garmin GPS V

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          • #6
            I've gotten two of them already from radio shack. They both put out a lot of heat.

            Do any other local stores offer voltage regulators?

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            • #7
              Out of curiosity, what manufacturer is the regulator that Radio Shack sells? There are quite a few companies that make them. I'd try to find a different brand.
              Rick S.

              XP Pro SP2, Soyo P4RC350 MB, Nvidia FX5200, 320W PS, Inverter & uSDC20D, 2.4GHz CeleronD320, 512MB DDR, 30GB 3.5", Pioneer 106s Slot DVD, Linksys WMP54G WiFi, Lilliput 7" & 4" TFT LCD, Zippy EL610 Keyboard, Touchpad, Garmin GPS V

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              • #8
                Originally posted by strohmrs
                Out of curiosity, what manufacturer is the regulator that Radio Shack sells? There are quite a few companies that make them. I'd try to find a different brand.
                all it says is the info given here
                http://www.radioshack.com/product.as...%5Fid=276-1770

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                • #9
                  It should have some kind of markings on it. They may have a less then ideal batch at your Radio Shack. They work and are within an acceptable temp range while in use. May as well use it for a while and see if it works out.
                  Rick S.

                  XP Pro SP2, Soyo P4RC350 MB, Nvidia FX5200, 320W PS, Inverter & uSDC20D, 2.4GHz CeleronD320, 512MB DDR, 30GB 3.5", Pioneer 106s Slot DVD, Linksys WMP54G WiFi, Lilliput 7" & 4" TFT LCD, Zippy EL610 Keyboard, Touchpad, Garmin GPS V

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                  • #10
                    I work there, and we get them from all manufacturers. All of our ICs come from the cheapest bidder. The one thing I would want to know is if the 7805 you have is made from plastic (sort of) or ceramic. I have seen both, and the plastic, although same ratings and all, gets hotter faster, even with a heat sink.

                    Just get some from Mouser. You'll pay for shipping, but you could get like 2 dozen of things for what we charge.
                    2000 Subaru OBS

                    Dell P3 @ 900 Mhz
                    7" Lilliput TS w/DigitalWW in-dash mount
                    80GB External HD

                    I am Zero Bitrate....

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                    • #11
                      The regulator could be oscillating; they can do that when there's no load on the output. Try putting a small capacitor across the output, like 0.01 to 0.1 microfarads. One across the input wouldn't hurt either.

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                      • #12
                        When not connected to mp3 player, the current draw is 300mA ---> 3.6W, with mp3 player, its over 500mA (off ammeter's scale)

                        The 7805 I have has the plastic coverings and has the markings ueML (mu epslon M L) then under it 7805A.

                        I tried putting a .1uf capacitor on the input and output, and it didn't reduce the heat.

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                        • #13
                          I went to another local radio shack and found the exact same model of 7805, identical umEA print on it.

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                          • #14
                            Unless you're willing to get one from another source, I wouldn't worry about the unloaded heat. It's still operating within normal specs when loaded. The temp isn't that bad as long as the space you put it into isn't too small and you already have it heatsinked. Try the install and monitor it closely for any signs of overheating the first few uses.
                            Rick S.

                            XP Pro SP2, Soyo P4RC350 MB, Nvidia FX5200, 320W PS, Inverter & uSDC20D, 2.4GHz CeleronD320, 512MB DDR, 30GB 3.5", Pioneer 106s Slot DVD, Linksys WMP54G WiFi, Lilliput 7" & 4" TFT LCD, Zippy EL610 Keyboard, Touchpad, Garmin GPS V

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                            • #15
                              OKOK I'll take it up the ... from shipping. What online store can a voltage regulator that doesn't make my heatsink sizzling to the touch?

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