protecting cctv circuits from surges BY Francois_Swart

Discussion in 'General Electronics Chat' started by bertus, Dec 27, 2011.

  1. bertus

    Thread Starter Administrator

    Apr 5, 2008
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    Hello,

    I found this message in my e-mail.
    As I do not answer emails I am posting the question over here:

    You can take a look at the EDUCYPEDIA for links on the MOV's:
    http://educypedia.karadimov.info/electronics/resistorsnon.htm

    Bertus
     
  2. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    @Francois_Swart

    How are these CTV cameras powered? Please post the voltage and maybe the camera model and manufacturer.
     
  3. Francois_Swart

    Member

    Jun 4, 2009
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    @praondevou

    The cameras are individualy powered, static cameras @12vDC and the PTZ @ 24vAC

    I will attach a few scans I made from the brochure.

    Also attached are the specs on the 2 Surge Protection units available from the supplier (Mustek security systems)

    To give a quick indication Why I say these devices (when purchased commercialy), are expensive: Static cameras +/- $140 PTZ Dome: +/- $750

    Surge Protectors (see attachments)
    DS-SP01: +/-$65
    DS-SP005-Q: +/- $130

    and one needs 2 surge protectors per camera, (one on the camera side, one on the dvr)

    So for my system consisting of 6X Static Cameras and 2X PTZ Domes and an 8Ch DVR:

    6X Statics @ $140ea= $840
    2X PTZ @ $750ea= $1500
    1X8Ch DVR @ $1200

    Surge Protection Required:
    12X DS-SP01 @ $65ea = $780
    4X DS-SP005-Q @ $130ea= $520

    Total For Surge Protection: $1300.

    Now I am Sorry but I am not Willing to pay $1300 for surge protection and there is stil not 100% certainty that I wont have to replace these camers or worse the DVR.
     
  4. tom66

    Senior Member

    May 9, 2009
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    Are these designed to reduce damage from lightning strikes?

    Perhaps suggest buying one of them and seeing how it works...
     
  5. Francois_Swart

    Member

    Jun 4, 2009
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    With a direct lightning strike I doubt that anything would survive.

    Induced voltages in the cables from a lightning strike, or a spike produced by the PSU or DVR or something to that effect seems more practical.

    One of my friends however bought a few of the DS-SP-005-Q's awhile back and stripped one (Waste of good money!) waiting for him to mail me the pictures he took of it. Might be worth while to reverse engineer the thing. I cant imagine that the components for all the protectors would be more than $65.
     
  6. tom66

    Senior Member

    May 9, 2009
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    Spikes in the PSU would be rare. Maybe a poor design of power supply would produce them.

    The protection components you list probably cost under $3 total. Add the connectors on each end, the case, and the assembly, it might be $5.
     
  7. Francois_Swart

    Member

    Jun 4, 2009
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    Multiply that by the 16 required and its roughly $80. Thats a big difference from $1300 wont you agree?
     
  8. tom66

    Senior Member

    May 9, 2009
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    I agree. It's massively overpriced. And prices reduce in quantity - it would probably be close to $0.80 ea. @ 1,000 qty, in my experience. Made in China, of course.
     
  9. Francois_Swart

    Member

    Jun 4, 2009
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    Yes, after all they do say "If you want something mass produced, just give it to the Chinese"

    Lets say that the price rises to $4ea with shipping and taxes. Its stil a HUGE difference. And the consumer pays for it.
     
  10. tom66

    Senior Member

    May 9, 2009
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    Breakdown of $800 for 1,000 units:
    $300 factory time 1-2 hours
    $200 components for 1,000 units
    $100 PCBs
    $150 tooling
    $50 shipping

    Maybe add $500 for cases.

    (This is from my experience when I quoted PCB manufacture.)

    And that's 1,000 items... just go to alibaba.com and look for almost any device (they probably list something similar) and you can see the markup of these retail and specialist stores is massive.

    ....

    Anyway, let's think about this device. So, it's designed to protect the camera and/or DVR from spikes in the power supply? Would it not be better to get a power supply which doesn't get spikes in the first place? What's the typical magnitude of these spikes? What is the source of them?
     
    Last edited: Dec 28, 2011
  11. Francois_Swart

    Member

    Jun 4, 2009
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    Link to an article on security systems and power considderations in general, which includes CCTV systems.
    http://ecmweb.com/mag/electric_power_quality_considerations/

    Do I see a bussiness opertunity? Then again I dont have time for it...

    As far as the PSU issue is concerned, I don't think there would be an issue with the 12vDC supplies they are (in my case) medium quality switchmode supplies with fused outputs. In my Installation planning I decided to run 2Core+E Surfix right up to the camera position and to install the camera on a enclosure, inside this enclosure i plan to place the PSU and the surge protection, it would also make my instalation neat (even if its only for my house), this is to compensate for voltage drop along the cable run. The cameras @12vDC pull a current of 400mA so I'd rather have the PSU as close to the camera as possible.

    There might be an issue with the PTZ Supplies, as they are just step down tansformers (230v-24v AC)

    Personally I think induced voltages from a lightning strike (we have huge thunderstorms in this area of South Africa) would be the biggest cause of transients. But our electrical supply isn't very stable either. The mains supply varies between 205v and 252v (Single Phase) and that has been with my own measurements, voltage spikes are not uncommon.

    I have spoken to my friend this morning and he has sent me an image of the components he striped out of his surge protector. Stil waiting for him to find the images he took of the circuit board itself.

    From left to right:

    090L Gas Tube Arrestor 90V Price ea: (1-25 qty) $0.50c
    075M Gas Tube Arrestor 75V Price ea: (1-25 qty) $0.50c
    ZOV 14D820K MOV 14mm RMS=50v DC=66v Price ea: (1-25 qty) $0.17c
    W60 XF030 Fuse Multi Fuse Ih=0.30 It=0.60 (1-25 qty) $0.17c

    The last 4 components I have been unable to identify by the part numbers, I wil include them in any case, but my thoughts are that they may be tranzorbs.

    XT 72A
    ZP 72A
    6.8C 68
    P008B 0642

    From the above and using my own deduction, I can guess that the components are grouped as follows:

    Video Signal:
    090L Gas Tube Arrestor 90V
    W60 XF030

    Video Ground
    090L Gas Tube Arrestor 90V
    W60 XF030

    Power +/AC
    075M Gas Tube Arrestor 75V
    ZOV 14D820K
    W60 XF030

    Power -/AC
    075M Gas Tube Arrestor 75V
    ZOV 14D820K
    W60 XF030

    RS-485 Data (TX or RX- unknown)
    XT 72A
    ZP 72A
    W60 XF030

    RS-485 Data (TX or RX- unknown)
    6.8C 68
    P008B 0642
    W60 XF030

    If these 4 unknown components are Tranzorbs they would be rated at 12v (or slightly above) as the RS-485 uses -7v to +12v.

    Any Input would be appreciated.

    PS: Appologies for the low res image.
     
  12. tom66

    Senior Member

    May 9, 2009
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    No, unfortunately I don't have the time to start a business like that, as I'm currently doing too much...

    If the problem is induced voltage, then shielding the power cables should be sufficient. With mains problems, you might consider a surge absorber (gas discharge tube would work well).
     
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