Silly LED Problem

[gsturgeon]

I replaced the cockpit light bulbs with LEDs as I found the original ones were too dim for me to read,worked perfectly, however when they are on, the TV reports 'No signal'!

One of the lights is directly under the TV aerial on the radar arch, perhaps this is the reason.

Is there anything I can do, or is it a lost cause? It is not possible to move either the light or the aerial.

 

[henryf]

It could be a number of things.

Have you disturbed a lead to the aerial when doing the work?

Do the new lamps draw more current and is the aerial fed from the same circuit? If so the aerial might not be getting sufficient current (I'm assuming its an amplified unit).

It could be that there is some form of interference. When I changed my nav lights to LED I was told some older / less good quality lamp could cause interference.

Henry

 

[EME]

I replaced the cockpit light bulbs with LEDs as I found the original ones were to dim for me to read,worked perfectly, however when they are on, the TV reports 'No signal'!

One of the lights is directly under the TV aerial on the radar arch, perhaps this is the reason.

Is there anything I can do, or is it a lost cause? It is not possible to move either the light or the aerial.

Almost definitely 'noise' as suggested. An issue with too many LED drivers (rather than LED itself). An additional capacitor/noise filter will resolve but frankly better to change the LED units for a better brand. If it is 'noise' then it has nothing to do with location but is travelling through the DC loop in all probability. It can also be an issue related to the number of DC units on the loop or even poor wiring in the boat ( only seen that once though).

 

[gsturgeon]

Almost definitely 'noise' as suggested. An issue with too many LED drivers (rather than LED itself). An additional capacitor/noise filter will resolve but frankly better to change the LED units for a better brand. If it is 'noise' then it has nothing to do with location but is travelling through the DC loop in all probability. It can also be an issue related to the number of DC units on the loop or even poor wiring in the boat ( only seen that once though).

Thanks people.

My knowledge of electronics leaves a lot to be desired- valves only in my schooldays! How big should the capacitor be and do I just wire it across the led terminals?

 

[EME]

Thanks people.

My knowledge of electronics leaves a lot to be desired- valves only in my schooldays! How big should the capacitor be and do I just wire it across the led terminals?

Still undoubtedly better than mine. The simple answer to location is as close as possible to the noise source ie the LED light unit.

However Ill step back a bit as I think it might be better to replace the LED itself. It is difficult to prove it really is 'noise' unless you do EMC testing or use a high quality oscilloscope (although that will only measure conducted noise). BUT, if the TV is experiencing some sort of interference when the lights on and the interference goes away when the lights are off, that should be adequate proof.

A 'real' noise filter normally has a common mode choke and at least two capacitors. The optimised capacitance of the noise filter depends on the frequency of noise and the actual installation. Normally two capacitors should be used, one is a larger capacitor for low frequency noise , the other is a smaller one for high frequency. However a large capacitor will filter low frequency noise and manage wiring issues ( we have found voltage fluctuation in cables the cause of most 'conducted' noise). Given that you might 'assume' a 10V input voltage the capacitor should be big enough for total wattages (in other words I havent got a clue!!) .

I dont think Ive helped much.

 

[Salty John]

Check that these LEDs don't interfere with vhf and ais communication. Certain types of driver can completely block out these communications - worth knowing if you need to switch off the lights before making your mayday call!