Expert needed to reduce/eliminate flickering on DVR

[GiovanniG]

Hi, I've the same issue in many systems I realized, the image suffers of flickering, and it is related to the HDD writes, each time HDD writes a flick appears on all cameras, usually the ones with longer distance have a bit less of that.

I am using a 12V 10A PSU with a 17Ah battery connected, this ensures me about 5/8 hours of surveillance when the power goes off, this creates the problem with the common ground, I'm aware of itm but using different PSU as somebody suggested needs a UPS, which has only few minutes of working time. Buy another PSU with battery increases costs and maintenance costs when it will need to replace batteries, it would better not doing it.

Analog cameras, connected by baluns on a 4 pair FTP cable, 3 pairs are used for power, one pair for video signal. On the DVR side (only) the shield of FTP cable is grounded with all other cables.
Touching the power concept isn't an option, since requires too much time and I really dubt it can help significantly.

I usually place on the DVR poer line a ferrite with many coils wrapped on, 2 coils exactly with same orientation (to have zero flux as result), one for positive and one for negative wire, and added 0,1uF capacitors too, this usually reduces the effect but not eliminate it. I've also tried to put it internally on the HDD power cable, to insulate the noise between HDD ground and DVR ground, but not great results.

What can I do? probably a DC/DC 12V/12V with galvanic insulation will solve the problem, I don't know if I can find cheap ones, any other suggestion? Thank you!

 

[bigredfish]

Show a brief video of this flickering.

It could be lines close in parallel to mains power, could be power supply, could be other things

 

[paul@austins.tv]

Your analogue DVR/cables and cameras are very very susceptible to RF interference. Never heard or experienced the hard drive's emitting the interference. I've fitted many analogue DVR's/XVR's systems in the past (now only NVR's/IP) and always tried to use full copper screened coaxial cables. So to eliminate RF interference. Perhaps it's time to upgrade to a modern IP NVR & cameras?

 

[GiovanniG]

thank you for answers, I upload here a piece of video.
No power suplly problems, if I stop record on HDD the flicker disappears, the image is stable as it should
Shortly I can assure you no problem of camera, cable (it's FTP + balanced with baluns on both side) of power supply.
For me no way to spend much money to trash all and switch to IP, too late.I need to correct. Much cheaper is to buy another PSU with battery and power the DVR separately, but what a waste.

If you have chance to try to power DVR anc camera with same PSU you probably will see the same effect.
The more sensor of camera is gaining for the low light conditions, the more you will notice flickering, looks the noise is going till the camera and spoil the signal, instead interfere with ADC converter of DVR, bu I can be wrong
I hope somebody with the same issue experience can give an idea, thank you

 

[GiovanniG]

I try to buy these DC-DC modules with ground isolation, it shoudl work.
Anyway I can't understand how HDD could create these RF interferences. Maybe it can be up to seagate too, as WD probably generate less impact

https://m.aliexpress.ru/item/0_1005008619235280.html?spm=a2g2w.orderdetail.0.0.77b34aa6HyRm6R&sku_id=12000045975749735&_ga=2.156945595.1421812835.1752786522-1705121917.1745418438

 

[bigredfish]

I had analog DVR and installed maybe a dozen for friends for years. I never saw a HD interfere with the image.

It still could be many things. Analog systems with that type of flicker are very hard to diagnose.

I would start with changing out the baluns and making sure the cable connections going to that camera are perfect at both ends. It doesnt take much

Is there a good simple explanation for the pulsing light running vertically where the arrow is?
How about the spot circled, near the end of the clip especially?

 

[GiovanniG]

Thanks for answer. I repaeat, with HDD not recording, no flickering. It's doesn't depend on other things, it depends on HDD writes, I'm 100% sure.
You probably always use different power adapters for cameras and DVR, in that case the problem will not appear, but you will have very limited working time without main electricity, what the UPS can do, usualy 10-20 minutes only. My choice to use one power adapter with one huge battery is to give the system at least 5 hours of recording without power, this is essential. With IP cameras it can be obtained only with 12V cameras, but only 2 pairs are available for power and on the long distance it can fail, IP cameras need much more power than analog cameras, this is wy they use PoE. PoE with 12V battery it's a problem, needs DC/DC upscaling.

My qestion is for experts who faced this problem and found a way to block RF noise coming from HDD when the common ground is connected between cameras and DVR

 

[TonyR]

Based on your replies to suggested reasons or remedies for the glitch I'd say you already know the solution but hesitate to implement it because of the expense.

If that's true, then you have a decision to make......either spend the money and fix the issue or save the money and live with the glitch......could it be that simple?

 

[paul@austins.tv]

I can understand the reason for the battery backup. Let's stick with the original problem with the interference.

If it's just one camera that has an issue with the flickering. Indeed I would suggest trying a separate 12 DC/2 amp power supply, just for that camera. Another possibility would be to reduce via the analogue camera interface, it's resolution. In the past I had some 4k CVI cameras and RF interference was apparent at 4k, lowering to 6MP, resolved the issue. Good luck.