Computer screen interference

[bag 'o' bones]

Question for the more knowledgeable regarding all things electrickery.

 

Working from the boat at the moment, My laptop is connected to a larger screen both running off the 12 volt using a couple of adjustable voltage boost adaptors.

 

 

The adaptors are connected to the main 12 volt supply using a splitter.

 

 

Problems:

 

The 12 volt splitter adaptor has gone pop. It is rated at 6.5 amp.

the screen (75w) requires 19 volt 2.6 amp and the laptop (60w) 19volt 3.2 amp

Im assuming boosting up to 19 volt means that the amp draw is beyond the capability of the splitter; therefore each adaptor requires a separate 12 feed from the battery bank.

 

Lap top running on 12 volt on its own - no problem.

separate screen running on 12 volt connected to the laptop on internal battery no problem.

separate screen running on 12 volt connected to the lap top also running on 12 volt results in annoying screen flicker. Disconnect the 12 volt supply to lap top and flickering stops.

 

If the laptop and screen run on the supplied AC brick supply there are no flicker problems. although its obviously silly boosting 12 volt to 230 through a big inverter and then back down to 19 volt!

 

Regardless of the set up, the equipment interferes with the radio which is annoying.

 

Hope the above makes sense! Any suggestions?

 

[bottle]

The splitter went pop because;

 

 

the screen (75w) requires 19 volt 2.6 amp and the laptop (60w) 19volt 3.2 amp

 

75 watts at 19v is 75/19 = 3.94 amps...60 watts at 19v = 3.15 amps

 

The splitter can only supply 12v * 6.5 amps = 78 watts.

 

As to the flickering and the radio interference that is something that has failed or does not have EMI ,protection.

 

Reference: WIKIpedia

[MoominPapa]

Ground loop. Most 12V adapters have the negative conductor of the input physically connected to the negative of the output. Therefore the negative of the DC inputs to the laptop and the monitor are connected with the negative of the batteries. The negatives of the monitor and the laptop are also connected via the video cable. Some of the power-supply current is flowing through the video cable rather than the power cables and causing the interference. AC adapters isolate the input and output for safety, so you don't seen this problem.

 

I had the same thing connecting the audio output of a laptop to a car-type radio. Cured with an audio isolating transformer. The solution for a video connection will likely be a lot more difficult. Either find an isolated DC adapter, or use an inverter an an AC adapter for either the laptop or the monitor.

 

MP.

[Martin Megson]

Regarding radio interference some 3g dongles and phones can interfere with DAB radios. I use my iPhone tethered and get interference if its within around 4ft of the radio.

[smileypete]

So you're running both lappie and monitor directly off 12V instead of 19V?

 

It may be that both loads are pulling the 12V to a lower level the monitor can't run off properly.

 

In any case I'd prefer a converter to give a cleaner supply than direct 12V, there's load of converters on Ebay, this should do for both, but won't cure inadequate 12V wiring.

 

http://www.ebay.co.uk/itm/NEW-Boost-Converter-Step-up-Module-Power-Supply-600W-DC-DC-10V-60V-to-12V-80V-/121505076291

 

cheers, Pete.

~smpt~

Edited December 18, 2014 by smileypete

[bag 'o' bones]

So you're running both lappie and monitor directly off 12V instead of 19V?

 

It may be that both loads are pulling the 12V to a lower level the monitor can't run off properly.

 

In any case I'd prefer a converter to give a cleaner supply than direct 12V, there's load of converters on Ebay, this should do for both, but won't cure inadequate 12V wiring.

 

http://www.ebay.co.uk/itm/NEW-Boost-Converter-Step-up-Module-Power-Supply-600W-DC-DC-10V-60V-to-12V-80V-/121505076291

 

cheers, Pete.

~smpt~

Both regulated adaptors are designed to boost 12 volt to a variety of voltages between 15 - 22 volt. I don't think its a problem with low voltage, moreover some sort of EM interference.

 

I've got a few ideas based on the above suggestions, will post further when I'm less tired.

Edited December 19, 2014 by bag 'o' bones