LED Lights Affecting TV Signal

Emjaytoo

Emjaytoo

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Us: Kent; Emjaytoo: Holland; Kate: Conyer Creek
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I have slowly been installing LED lights in the boat. A couple of years ago I fitted LED strips under the lockers running down both sides of the saloon and earlier this year I replaced the two aftmost saloon halogens with LED lamps. The results have been very sucessful - good light levels at a fraction of the current draw.

This afternoon I replaced the two foward halogens in the saloon with LED lamps. A couple of hours later whilst watching the TV which is mounted on the forward bulkhead, I switched the lights on and the digital TV signal dissappeared!

Various trials have demonstrated that it is the two forward headlining mounted LEDs that completely kill the digital TV reception. The other LED lamps which are further away have no effect. Strangely, the LED strips, one of which terminates a mere 500mm away from the TV also have no effect. The nearest LED lamp is over a metre away. As soon as the lights are switched onthe signal returns.

Can anyone shed any light on this? (sorry about the pun!)
 
Some led's have electronic voltage stabilisers in them, try moving them around, but yes I get radio interference from some LEDs & the 12v fluorescence tubes. Dunno about TV, I wouldn't have one on board.
 
Emjaytoo said:
I have slowly been installing LED lights in the boat. A couple of years ago I fitted LED strips under the lockers running down both sides of the saloon and earlier this year I replaced the two aftmost saloon halogens with LED lamps. The results have been very sucessful - good light levels at a fraction of the current draw.

This afternoon I replaced the two foward halogens in the saloon with LED lamps. A couple of hours later whilst watching the TV which is mounted on the forward bulkhead, I switched the lights on and the digital TV signal dissappeared!

Various trials have demonstrated that it is the two forward headlining mounted LEDs that completely kill the digital TV reception. The other LED lamps which are further away have no effect. Strangely, the LED strips, one of which terminates a mere 500mm away from the TV also have no effect. The nearest LED lamp is over a metre away. As soon as the lights are switched onthe signal returns.

Can anyone shed any light on this? (sorry about the pun!)
Click to expand...

The only LED lamps that will not generate EMI (Electro-Magnetic Interference) are resistor controlled lamps, unfortunately these lamps have a poor working life when used on boats. The variable voltage and voltage transients often generated on marine systems regularly damage this type of LED lamp and they fail prematurely as a result, giving LED a bad and unwarranted reputation. Your LED strip will be resistor controlled hence no interference problems but do be careful when this is used with your boat engine running or when on shore charger. Flexible strip is designed for fixed voltage on shore not on your boat. Any voltage over 12V will damage the LEDs due to overheating arising from excess current.

To overcome variable voltage issues constant-current controlled LED lamps should be used on boats, I suspect your latest lamp purchase will be of this type. Constant-current controlled lamps vary very much in quality with all using some form of controller that ensures that a steady current flows through the LED lamp, irrespective of variation of the supply voltage. Many of the Chinese lamps sold cheaply, for instance on eBay are not CE certified, even if they say they are. Manufacturers of low cost lamps often buy the cheapest components, not surprising when many lamps are sold for 50p or less. Typical low cost, so called, constant current LEDs use current-control methods that utilise switch-mode converters. These components and can contribute significantly to both conducted and radiated Radio Frequency (RF) emissions. These can interfere with AIS, VHF, FM, SSB and GPS radios and TVs on board. This EMI is typically due to the low cost LED driver IC's which create sharp spikes when switching high frequency wave-forms and thus emit RFI into the air and also may cause EMI to be carried through the boats wiring system. This problem is compounded by poor design of the typical LED emitter boards, where the copper tracks tend to work as mini-antenna. We address both of these important issues in our own LED driver and board design. 'Certified' CE approval of LED lamps means that the design has passed EMI tests which ensure that the lamps do not emit interference above a minimal level.

However EMI problems are sometimes compounded by the type of electronic receivers in use. In my experience modern good quality equipment is often much better protected by built in filters, whereas older kit and budget equipment less so. In practice one type of receiver will be unaffected whereas another won't function at all. No constant-current LED lamp will be EMI free but the better ones are well designed and emissions will be minimised. Fitting of capacitors and ferrites can help but that can be at best tricky and sometimes not practicable.

Regards
 
I've used only the type of LED that uses resistance to drop the voltage rather than those with a switch mode power supply.
So far about 5 years from the oldest, and no failures yet. But at the price of the Chinese imports, easy to just carry some spares. I recently bought 20 for the price I'd pay for one locally.
 
Adrian Jones said:
The only LED lamps that will not generate EMI (Electro-Magnetic Interference) are resistor controlled lamps, unfortunately these lamps have a poor working life when used on boats.
Click to expand...

Adrian, you are building a case in favour of resistor controlled LEDs on boats :p I agree with MM5AHO that experience suggests that used sensibly (ie not when the engine is running) the resistor LEDs are fine and avoid the interference issues. The mass Chinese suppliers though seem to be moving fast to all regulated LEDs, so the option won't even exist for long.
 
VicMallows said:
Adrian, you are building a case in favour of resistor controlled LEDs on boats :p I agree with MM5AHO that experience suggests that used sensibly (ie not when the engine is running) the resistor LEDs are fine and avoid the interference issues. The mass Chinese suppliers though seem to be moving fast to all regulated LEDs, so the option won't even exist for long.
Click to expand...

Resistor controlled lamps are fine if used at the voltage they are designed for. However if a lamp is designed for 12 Volts for example a flexible LED strip and you connect 13.8 volts to it it will increase the current through each LED by 50%. If you increase the voltage to +16V which smart battery chargers do when cycling in equalisation mode you will double the current through the lamp. I have seen instances where these type of currents result in LED strip smoldering as the cheap strip PCB tracks are microns thick. People argue that most resistor controlled lamps are made for cars and the control resistors are rated for 13.8V, absolutely right, but the light output at 12V is significantly less than it is at 13.8V. A case in favour for resistor controlled lamps, I think not!

There are regulated lamps and regulated lamps, I described the effect of poor quality regulators have and know the cost of the good quality control IC. You cant buy one, even in China, for the cost that some Chinese vendors are selling 5 of their lamps for. You can buy cheap engine oil, but you probably don't when you look at the specification. People buy lamps from unknown vendors with little or no warranty and certainly no specification and put them into their boats costing tens or hundreds of thousand of pounds, its incredible. Most of the lamps are imported by post from China thus they avoid EU quality standards. All my LED lamp imports have to be certified CE and signed off by HMRC as meeting EU quality standards. People are being conned into thinking the cheap Chinese lamps that use sub standard components meet EU safety standards. Take it from me that many don't and the back door trading that is designed to avoid safety standards needs to be looked at before we have a significant tragedy.
 
Originally Posted by Adrian Jones
The only LED lamps that will not generate EMI (Electro-Magnetic Interference) are resistor controlled lamps, unfortunately these lamps have a poor working life when used on boats
Click to expand...
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Not true. If you use properly designed and shielded constant current supplies on your Led's then you will not have any trouble with EMI

Part of the problem is that people fit 20 or more led lights each with their own constant current supply, mixing suppliers and manufacturers. Spreading potential sources of EMI around the boat.

A far better solution is to estimate the total power required by the boat led's ( interior lighting, deck and nav where fitted ) and fit a single, central, well designed and screened, stabilised power supply and use it's output as a separate bus to drive all of these fittings that can now use simple led's with cheap resistor current limiting.

There are several advantages in this. Voltage is kept stable under a wide range of input conditions. Most supplies will protect the delicate leds downstream from spikes, potential polarity reversals and possibly even nearby lightning strikes. Cheaper led lights can be used safely and without light level variations. EMI source can be well isolated and shielded.
 
I would suggest powering the TV from a separate battery, to see whether the interference is radiated or conducted.
If conducted, filtering the supply to the telly may cure it.
If radiated, try moving the tv aerial, or see if its possible to twist together the supply and return wires to the lights.
Or rearrange the wiring so there is not a large loop carrying the current.
Try filtering each light with a 10nF or similar capacitor across it.
Or a ferrite choke, perhaps? The sort found on some computer leads are useful.
It is possible to sort out switch mode voltage regulators from an interference perspective, but it's a lot easier to do at the design stage.
So it may be easier just to find a different brand of bulb.

Personally I prefer resistor limited LEDs and don't use a smart charger. If we had a high voltage charging regime, I think regulating the lighting circuit at the fuse board would be wise.
A linear low dropout regulator probably.
 
EugeneR said:
I did not realise HMRC could sign off on quality standards?
Click to expand...

Indeed they now have a role in quality standards and almost every other aspect of modern life!

The removal of EU internal borders in 1993 did not mean diminished importance for European Customs, their activities go well beyond what you may realise.

The Customs part of HMRC has changed and now includes surveillance of imports. The scope of their surveillance is based on 339/93/EEC Council Regulation (EEC) No 339/93 of 8 February 1993 which relates to checks for conformity with the rules on product safety in the case of products imported from third countries. Safety includes EMC compliance.

Focus is on products that are a serious and an immediate risk to health and safety and lack compulsory marking, label or documentation. Since January 1996 the European Commission and the Member States have enabled customs administrations, through a well-funded program, to become efficient and perform as one single and unique administration. Implementation includes monitoring, studies, organization of seminars, working parties, exchange of officials, publications of manuals, information and communication actions, IT systems and training actions. We have experienced HMRC referring an import to the HSE, the UK body tasked with monitoring goods via Trading Standards department of Local Authorities.
 
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