# protecting cctv circuits from surges BY Francois_Swart

#### bertus

Joined Apr 5, 2008
21,041
Hello,

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

hi bertus,

i was wondering if you know anything about surge protection?

i recently bought a few cctv cameras and want to add surge protection, but the devices available comecialy are in my opinion to expensive...

its just a mov, gdt, ptc fuse and tranzorb as far as i can gather but putting it together with my limeted knowladge would mean a disaster.

thanx for your time
You can take a look at the EDUCYPEDIA for links on the MOV's:

Bertus

#### praondevou

Joined Jul 9, 2011
2,942
@Francois_Swart

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

#### Francois_Swart

Joined Jun 4, 2009
14
@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.

#### tom66

Joined May 9, 2009
2,595
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.
Spikes in the PSU would be rare. Maybe a poor design of power supply would produce them.

#### Francois_Swart

Joined Jun 4, 2009
14
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. 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.

#### tom66

Joined May 9, 2009
2,595
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: #### Francois_Swart Joined Jun 4, 2009 14 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?
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.

#### Attachments

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#### tom66

Joined May 9, 2009
2,595
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).