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Silly regulator question

Discussion in 'General Electronics Discussion' started by James Fraser, Jul 31, 2017.

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  1. James Fraser

    James Fraser

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    Jul 31, 2017
    Hi All,
    Silly question for you. I am currently into the quad hobby at the moment. My recent issue is that I'm trying to power some devices from the flight controllers power. It has a 5v 0.5a and reg Onboard and I require something near 1A would it be an issue to swap to a 1A reg?

    Many thanks.

    James
     
  2. BobK

    BobK

    7,682
    1,686
    Jan 5, 2010
    Assuming the source can provide 1A, you can, but you might need too add or increase to the heat sinking.

    What is the input voltage? This will determine how much power is dissipated.

    Bob
     
  3. James Fraser

    James Fraser

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    Jul 31, 2017
    The power input is 11-14v and the battery can supply 100A+ at burst to the motors. It's the on board implications I'm worried about. Assuming the voltage will be between 11-14v what would the max temp of the reg be at 5v drawing the max of 1a which it will never get to. Real world max current draw will be 700ma at best.

    Many thanks Bob.

    James
     
  4. AnalogKid

    AnalogKid

    2,393
    665
    Jun 10, 2015
    Without part numbers or a partial schematic it is impossible to say for sure.

    There are two basic types of voltage regulators, linear and switching. Linear regulator power dissipation is simple:
    (input voltage - output voltage) x current
    (14 V - 5 V) x 1 A = 9 W

    Switching regulators are much more complex circuits; the efficiency depends on both the design and the specific components used in that design. For example, two different output rectifiers that both work well could alter the overall efficiency by 5-10%. For very round numbers, assume an efficiency of 75%; for every 3 watts in the load, there is 1 watt of heat in the regulator.

    ak
     
  5. James Fraser

    James Fraser

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    Jul 31, 2017
    Here is component I'm wishing to use MC7805ECDTX.

    Thank.you AK

    James

    P.s. how to I attach a PDF to post ?
     
  6. AnalogKid

    AnalogKid

    2,393
    665
    Jun 10, 2015
    That is a classic linear regulator. For a constant input-output voltage differential, the power dissipated in the device is directly proportional to the current. If it was running how at 0.5 A, it probably will be too hot at 1 A without additional heatsink area.

    ak
     
  7. James Fraser

    James Fraser

    5
    0
    Jul 31, 2017
    No problems with 0.5a temp at the moment. I just want to use a higher current output for head room. Don't particularly want the quad falling out of the sky. My current calculations have me at 410ma for everything I need to power. So it's close to the max output for current regulator. Both the 0.5A and 1A regs are smd to-252.
     
    Last edited: Jul 31, 2017
  8. James Fraser

    James Fraser

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    Jul 31, 2017
    Or would it be better to use a step up step down regulator to mitigate the temp?
     
  9. Arouse1973

    Arouse1973 Adam

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    1,081
    Dec 18, 2013
    Hi James
    A buck regulator will be much better in terms of efficiency than a linear regulator. However they do produce a bit of switching noise which you may have to filter out with an LC filter on the output.
    Adam
     
  10. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    davenn likes this.
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