Electrical interference on monitor.. Any ideas?

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NitroJoe
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Electrical interference on monitor.. Any ideas?

Post by NitroJoe » 22 Dec 2013, 20:26

Hi folks,

I have wired up a screen and 12V light source using the same rocker switch. When the lamp is on, the screen has diagonal lines running across it, affecting the image. When I disconnect the lamp, the picture is perfect..

I have tried putting the switch on both neg and pos cables, to no avail. Anyone have any ideas what's up? Could the switch amperage be too low? I have a similar project which works fine, only difference is the switch..

Thanks in advance,

Joe

sedstar
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Re: Electrical interference on monitor.. Any ideas?

Post by sedstar » 22 Dec 2013, 21:38

video and audio are susceptible to multiple types of interference, there might be some small filter, or shielded wire/connectors that might sort you out.

a shielded wire, has an outer metal covering, thats connected to ground. ANy stray signal that cuts the field of the wire, has to hit the shield, which runs it to ground to be harmless.

Note that a shielded cable is useless if it runs thru an UNshielded connector... you generally want all shields and GND connected to the same GND...
Well, I understand that, boys... but see, my CAT gets the silly idea you're making fun of HIM... then he gets, *really* mean...

sedstar
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Re: Electrical interference on monitor.. Any ideas?

Post by sedstar » 22 Dec 2013, 21:57

on formal logic... i home in on the following quote from you...

"I have a similar project which works fine, only difference is the switch.."

similar? or same? a differrennt light (or same light different driver) or different screen or different cam MIGHT also be it... is your light/driver using a "boost" circuit? my memory tickles me something abou there no way to boost voltages without a COIL, which by its species makes it generate some interference.

but, if you eliminate most/all everything else... logic dictates you look at the switch...

IDEA... disconnect the switch and try even temporary hard wiring it? or, try "bypassing" it with a test lead... see if the problem goes away...
Well, I understand that, boys... but see, my CAT gets the silly idea you're making fun of HIM... then he gets, *really* mean...

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NitroJoe
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Re: Electrical interference on monitor.. Any ideas?

Post by NitroJoe » 22 Dec 2013, 22:10

Thanks Sedstar, of course you are right about removing the switch from the equation but after trying several things I basically got a bit fed up! :crazy: I will try to bridge it tomorrow and see if that makes any improvement.

The differences between this and the other setup are the cable lengths and the switch. Same screen, LED, driver, power source etc etc

I'll post up results tomorrow evening hopefully :thumbup:

genisis22
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Re: Electrical interference on monitor.. Any ideas?

Post by genisis22 » 23 Dec 2013, 08:04

hi as a thought, is your lamp and screen attached to your scope with mounts, I had a simular problem once and a wrap of black insulation tape under/between scope mounts and scope tube sorted it, no real idea why, possibly the torch ground was partly tracing through the scope mount to scope body making the torch driver pulse as it were, any way worth a try if all else fails , just dismount torch from rig and hand hold it, if all ok insulate torch from scope

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chas
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Re: Electrical interference on monitor.. Any ideas?

Post by chas » 23 Dec 2013, 11:45

Having power cables and AV cables running side by side doesn't help especially if they're wrapped up together in a loop or similar.
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some bloke
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Re: Electrical interference on monitor.. Any ideas?

Post by some bloke » 23 Dec 2013, 11:50

Might be a long shot but way back when in my 10/10 till we do it again days I was advised that certain lengths of antenna cable were to be avoided because they caused wavelength issues.
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Marky610
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Re: Electrical interference on monitor.. Any ideas?

Post by Marky610 » 23 Dec 2013, 17:25

NitroJoe wrote:Hi folks,

I have wired up a screen and 12V light source using the same rocker switch. When the lamp is on, the screen has diagonal lines running across it, affecting the image. When I disconnect the lamp, the picture is perfect..

I have tried putting the switch on both neg and pos cables, to no avail. Anyone have any ideas what's up? Could the switch amperage be too low? I have a similar project which works fine, only difference is the switch..

Thanks in advance,

Joe
I'd put money on the driver for your lamp ;)
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snoopy
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Re: Electrical interference on monitor.. Any ideas?

Post by snoopy » 23 Dec 2013, 18:15

Marky610 wrote:
NitroJoe wrote:Hi folks,

I have wired up a screen and 12V light source using the same rocker switch. When the lamp is on, the screen has diagonal lines running across it, affecting the image. When I disconnect the lamp, the picture is perfect..

I have tried putting the switch on both neg and pos cables, to no avail. Anyone have any ideas what's up? Could the switch amperage be too low? I have a similar project which works fine, only difference is the switch..

Thanks in advance,

Joe
I'd put money on the driver for your lamp ;)

me too..

run the lamp off of a seperate battery too see
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NitroJoe
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Re: Electrical interference on monitor.. Any ideas?

Post by NitroJoe » 23 Dec 2013, 21:19

Hi all,

Thanks for the ideas, I haven't tried anything out yet, but by elimination: It can't be earthing through the scope as it is the same when removed from the gun and it can't be the lamp driver, as it works in the other set up. It's not just 'the same as` the other lamp, it is the very same one.

I will try some more things over Xmas and come back to this. My money (and hopes) are still on it being the switch... :?:

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