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12v to 5v cctv

Discussion in 'Power Electronics' started by deanofire, Dec 20, 2020.

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  1. deanofire

    deanofire

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    Dec 20, 2020
    Hi there
    i have an old cctv system that is 12 v powered from a professional multi 12v power supply
    i have just changed over to new wifi type cameras which are 5v powered.
    I bought some 12v to 5w 3A (15w) buck convertors and these worked fine on my smaller neos/wyze cameras , but i have just obtained some new imou looc cameras that are also 5v and accordig to the specs 2Amp 6 W, but these will not work with the buck convertors.
    The power light comes on but the do not connect, as soon as i plug them back into the usb power supply (5v 1 Amp) they connect.
    the run of the old 12v cable is about 20-25m , could this be the cause ? i have connected them through the bucks indoors from an old pc supply and they work fine.
    Any ideas please ?
    thanks in advance
     
  2. Martaine2005

    Martaine2005

    3,101
    851
    May 12, 2015
    Can you check the voltage drop with a DDM?.
    What cable are you using for the 12v cams?.

    You can adjust some buck/boost converters, so voltage drop could be compensated for.

    Martin
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    10,833
    2,442
    Nov 17, 2011
    Yes, but that will make the voltage at the camera end depend on current consumption. Short current spikes will lead to dips in the supply voltage of the camera.
    The imho better option (if physically possible of course) is to place the step down converters in a small box at the camera end of the cable and power the cable as before from 12 V. This setup reduces current through the 12 V cable and ensures a stable 5 V supply at the camera end.
     
    Martaine2005 likes this.
  4. Martaine2005

    Martaine2005

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    May 12, 2015
    Good point and a good idea of placement.

    Martin
     
  5. deanofire

    deanofire

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    Dec 20, 2020
    thanks for the reply
    I am using the buck convertor at the camera end, i have checked with a multimeter and still have 12v at the camer end of the cable.
     
  6. deanofire

    deanofire

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    0
    Dec 20, 2020
    hi thanks for the reply
    i am still getting 12v at the camera end of the run
    i am afraid its just a cheap ebay type twin cable with power and BNC plug
     
  7. Martaine2005

    Martaine2005

    3,101
    851
    May 12, 2015
    The only way to be sure is to check the current requirements of both old and new cameras.
    You can check this by putting your multimeter in series with PSU and camera. If you do this indoors at the PSU end, then at the camera location. This test should give you an idea of any losses in the cable.
    The worst scenario is changing the cable for a heavier gauge cable.

    Martin
     
  8. deanofire

    deanofire

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    Dec 20, 2020
    Thanks
    i will give this a try
    unfortunately changing the cable is out of the question because it was laid as the house was being built lol
    thanks anyway
    Dean
     
  9. deanofire

    deanofire

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    Dec 20, 2020
    Hi All. i have just connected the same camera to another point with the same cable and supply but it is a shorter run nearer to the supply, and the camera works perfectly, so it would seem the distance (length of cable) is the problem
    My question is, i actually have 2 power leads at the point where i need to put my new camera. Could i connect the two power leads together to still give me my 12 v for my step down convertor that would boost my power enough to work ?
    TIA
     
  10. Harald Kapp

    Harald Kapp Moderator Moderator

    10,833
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    Nov 17, 2011
    Please draw a schematic of what you want to do. A verbal explanation is so imprecise.
     
  11. deanofire

    deanofire

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    Dec 20, 2020
    Hope you can understand this

    12a.jpg
     
    Last edited by a moderator: Dec 31, 2020
  12. Harald Kapp

    Harald Kapp Moderator Moderator

    10,833
    2,442
    Nov 17, 2011
    You can do that if the power source (to the left, not shown in your schematic) is the same for both cables.. You then effectively connect the cables in parallel.
    If the two cables are powered by separate 12 V sources, you should not make such a parallel connection. The two power sources will not be 100 % identical and the one with a few millivolts higher output voltage will force current back into the output of the one with lower output voltage. This can destroy this second power supply (not necessarily, but possibly).
    In that case I see no need for parallel cables.
     
  13. deanofire

    deanofire

    13
    0
    Dec 20, 2020
    Hi
    The two separate cables are both running from the supply box shown below.
    I have two feeds running side by side that used to feed two separate 12v cameras
    the problem seems to be due to the loss of power over the distance of the cable run, that is why i suggested the idea of the two 12v feeds being connected together in parallel before they enter the 12v-5v drop down convertor.
     

    Attached Files:

  14. Harald Kapp

    Harald Kapp Moderator Moderator

    10,833
    2,442
    Nov 17, 2011
    Give it a try, but with the 12 V to 5 V converter at the other end, the voltage drop along the cables must be considerable if a single cable doesn't suffice.
    Have you checked the output of the converters? Is it 5 V? You may be able to adjust the output voltage if need be.
    Anyway, connecting the 2 cables in parallel should at least not create additional issues.
     
    deanofire likes this.
  15. deanofire

    deanofire

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    0
    Dec 20, 2020
    Thanks
    i wll give this a try
     
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