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Topic: How to stop interference is camera cable? (Read 3474 times) previous topic - next topic

Seedler

Hi,

Don't know if this is in the correct place.

I am helping a friend with an experiment recording video and playing sound under water in a cage.  This is controlled by an Arduino on a floating platform at the surface.  The surface box also contains a battery and dvr.

This is the camera used:
https://www.ebay.co.uk/itm/30M-HD-1200TVL-CCTV-Camera-Underwater-Fish-Finder-For-Ice-Sea-River-Fishing-G6Q5/263590542681?hash=item3d5f387d59:g:ndgAAOSwMalaxvPr

The speaker cable is two core flex.

The camera and speaker cable are taped together and cable tied to rope on cage.

Problem is when speaker is on the picture from the camera is mostly just noise.  When speaker is off the video is ok.

Can I shield either the speaker or camera cable without replacing them?  Would a shield connect to battery negative?

Is there any other way of removing interference from video signal?

I have added two pictures to show my problem.  The bad one is with speaker on.

Hope someone can help.

Thanks,

Damien.

MarkT

You have a class-D audio amp driving the speaker?  Change to a linear amp will fix it.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Seedler


Paul_KD7HB

I do.  What class is linear?

Most linear is class A. Next is some version of class B.

Paul

Grumpy_Mike

Quote
Is there any other way of removing interference from video signal?
Once the noise is on the picture there is not much you can do. Best not let it get on in the first place.

However it does not look like noise to me. Noise is speckled, that looks like you have wiped out the sync pulses. It could be a power supply issue, look at the video signal on a scope.

Seedler

I don't have a scope.  Would this be a case of connecting neutrals?

Would shielded cable solve this? Would I need to shield speaker cable or video cable, or both?  I don't want to have to rewire if I don't have to.

I'll give the linear amp a go.

Thanks.

Grumpy_Mike

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Would this be a case of connecting neutrals?
Grounds yes but neutrals are things used in mains wiring and you should not connect them together.

Quote
Would shielded cable solve this?
It would help but is not a grantee cure.

 
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Would I need to shield speaker cable or video cable, or both?
Both would be better.

Quote
I'll give the linear amp a go
That is a very good first step, to drastically reduced the interference you are generating in the first place.

ted


ted

Locate source of the problem.
Take everything from the water - any changes ?
Use separate power supply for camera - any changes ?

Seedler

Hi,

I have to keep speaker in the water because it cant be powered dry, but I will try separate power supply.

What does wiped out sync pulses mean?

Does anyone know of a class-A 30watt mono board that runs off 12vdc.  Everything I find runs on 12vac.

Thanks,

Damien.

Grumpy_Mike

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What does wiped out sync pulses mean?
Wipe out means destroys.
Sync pulses are the bit of a composite video signal that tells the receiving TV that each line and each frame has started.

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Everything I find runs on 12vac.
That is because the amplifier is making a split supply with the input voltage. That implies you are not looking at class A amplifiers but class B.

ted

#11
May 02, 2018, 04:54 pm Last Edit: May 02, 2018, 04:55 pm by ted
put it in a bucket of water

You may have interferences from speaker wires,they act as transmitting antenna, water can increase the interferences ........
Try for speaker twisted pair cable or coax cable

Sync pulses

http://www.ni.com/white-paper/3020/en/

You don't need to change amplifier, you need locate the source of  interferences.

Seedler

Hi,

Problem is the speaker belongs to university. It came pre-wired with 20 meters of two core flex. I don't want to rewrite it with twisted pair or coaxial if I don't have to.

I will put speaker in water tomorrow and start testing

ted

If you don't want to touch the wires you have only 1 option which may work - battery for camera.
What happens when camera is not in the water ?

Seedler

Mike Ted, yous were rite, power supply.  Tried separate battery for dvr and camera and picture stayed clear, even with sound on.

I tried powering dvr separately and camera separately with varying results, but the best result is dvr and camera on the same battery and Arduino and speaker on another battery.

So my question now is, how do I run this off the same battery?  My setup is for a single 12v battery.  Can I filter the power to the dvr/camera somehow, or make them think they are on a different battery?

Thanks for all your help,

Damien.

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