Led interference

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Graham_Wright

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When working on the boat, I listen to a mains radio. I have some deck head led lights three leds in each. Each group is connected via a little white box containing what appears to be a bridge rectifier (to dodge the polarity issue I assume), an inductor, a capacitor and a surface mount something. Is it likely that this little box generates high power pulses to increase the apparent brightness and it likely that this generates the interference my radio suffers from? If so, what can I do about it? I could bypass the "little white box" I guess.
 
Graham,

Don't know about your box but we also have interference on our digital radio from internal LED light but only the closest to the aerial, this light is approx 2ft from the aerial the next closest light doesn't interfere which is 6ft from the aerial, our radio is digital not analogue, have you tried moving the location of the radio?
 
Graham_Wright said:
When working on the boat, I listen to a mains radio. I have some deck head led lights three leds in each. Each group is connected via a little white box containing what appears to be a bridge rectifier (to dodge the polarity issue I assume), an inductor, a capacitor and a surface mount something. Is it likely that this little box generates high power pulses to increase the apparent brightness and it likely that this generates the interference my radio suffers from? If so, what can I do about it? I could bypass the "little white box" I guess.
Click to expand...

Well you won't have this trouble with the tried and tested incandescent bulbs! Fit one or two low power ones which be used instead of this modern troublesome new fangled stuff when you want to listen to the radio.
 
I don't think there's an interference problem with "new fangled" low-cost unregulated LED lights. Even though I haven't had any fail after 3 years or so, maybe they're a bit flaky at 14.4 volts. But what the heck, buy a few more as spares ... ...
 
RF interference is common on many lower cost LEd units, the switch mode supplies they use are badly filtered, Ferrite beads are unlikely to help
 
The circuitry is an advanced way of controlling the current to LED's rather than using a resistance. The power is "pulse width modulated" to chop the current and voltage down to the level required. A resistor will do the same thing but will generate heat from the power dissipated, the power used will be much greater too. The PWM method is low loss. The PWM chopping will generate intereference the level of which depends on the quality of the unit and frequency.
 
I have the same problem with Led interference, the Led lights being bought from someone who posts on this forum occasionally (or at least used to). When I phoned to query this problem, I was told to buy a better quality radio!!

I now use my mobile phone for radio. I did try the ferrite rings as someone has suggested and it did not make a blind bit of difference.
 
This light fitting does sound like it has a switch mode power supply to control current. As said if you fit cheap LED from China with just a simple resistor current limit you will not get interference form the LED light. However they can suffer from too bright, too hot, damage at high battery volts like over 14 and a bit dim on low battery volts around11.
Depending on the layout and construction of your LED light fitting you may be able to wire all 3 LED in series and connect to 12v supply via a resistor. You need to drop about 3v at the current of the LEDs which can be what the original design draws. Or just try about 50 ohms and compare brightness to original. If a bit dim fit a lower value resistor. 2x50 in parallel or if too bright 2x50 in series. You may even be clever /lucky enough to be able to fit a switch to go from switch mode to resistive current limiting depending on concern re interference. good luck olewill
 
savageseadog said:
The circuitry is an advanced way of controlling the current to LED's rather than using a resistance. The power is "pulse width modulated" to chop the current and voltage down to the level required. A resistor will do the same thing but will generate heat from the power dissipated, the power used will be much greater too. The PWM method is low loss. The PWM chopping will generate intereference the level of which depends on the quality of the unit and frequency.
Click to expand...

Whaat about wrapping the circuitry in a bit of aluminium foil?
 
Graham_Wright said:
When working on the boat, I listen to a mains radio. I have some deck head led lights three leds in each. Each group is connected via a little white box containing what appears to be a bridge rectifier (to dodge the polarity issue I assume), an inductor, a capacitor and a surface mount something. Is it likely that this little box generates high power pulses to increase the apparent brightness and it likely that this generates the interference my radio suffers from? If so, what can I do about it? I could bypass the "little white box" I guess.
Click to expand...

Some time ago I had interference on my VHF comms radio that I found was due to my PWM solar regulator when the battery was getting to full charge.

I fitted a couple of big electronic caps across the output of the regulator and this solved my problem.
 
The problem is actually in the camper van (I lied!). During major alterations I am using a mains radio with a primitive aerial. The tv is fed from a "saucer" aerial, the amplifier for which has a radio output. We haven't suffered interference on the tv with lights on so I guess the radio will be ok as well.
I could bypass the electronic box and introduce a series resistor. It would be interesting to see if the (apparent) brightness decreases.
 
Thistle said:
Whaat about wrapping the circuitry in a bit of aluminium foil?
Click to expand...

The foil would have to be earthed to be effective, it might work a bit but it will be hard to do well. The other and probably main issue is radiation from the cabling to the light. You can reduce interference by keeping the positive and negative runs close together or even twisting them round each other. Don't create large open loops of cabling of one polarity so if you're wiring to and from a switch take both wires to the switch, wire the positive through the switch and take both supply cables out again. As already suggested ferrite cores installed round the cables near the light plus capacitors across the supply near the light but on the supply side of the ferrite .
 
I would just use a crisp packet to shield it.

For those who don't " get " this, search the news for "playing golf crisp bag"
tross
 
I'm confused...Are you using LED lighting that is plugged into the mains via a voltage adapter box? Because I cannot see any other reason why you could get interference when using LED's. I use a flexible, self adhesive, warm light LED lighting strip in my boats cabin. It's stuck inside a special aluminium extrusion channel, which not only acts as a heat sink but as convenient place to clip on the special diffuser made for it, and of course to allow it to mount easily to the ceiling. It's about a metre long ( draws 4 Watts/m) and it's fed direct from the battery, so there is zero interference on my boats car radio. You can get such strips in pure colours, such as red, green or blue, or you can even get colour changing versions that come with a remote control, that can be manually set to any colour in the rainbow or you can set it to automatically cycle through every colour. They are not that expensive either.
 
Some LED bulbs use simple resistors to convert +12V to the constant current that LED elements need. Others use various switch-mode converters which may cause interference.
Mains LED bulbs are more likely to use switchmode conversion, but not necessarily. Sometimes there is just a capacitor in series to reduce the voltage, followed by a simple resistor and rectifier.

The tape strips of LEDs just use resistors, they are great IMHO.

Mains LED bulbs which are dimmable generally use a switchmode chip which senses the waveform from a mains thyristor dimmer, these are often the noisiest in interference terms.

The remote controls which you put in series with the LED strips are also switchmode controllers of a sort, they may create interference if set to less than 100%
 
I have some LED strip lights as well and they are current regulated by built-in resistors. More "sophisticated" lights have a pulse width regulator that drops the effective voltage to 12v from as much as 15v and allegedly prolongs their active life - and potentially generates RF interference. All my strip and other lights are simple resistor regulated and do not fail, in spite of the variable supply voltage.
 
Depending upon the spec of the LEDs they will probably run OK on 12v. Or, it might be worth trying a DC-DC converter if you want a stable supply.

I have 1.6m of the LED strips. 8 x flush fitted LED lamps (quality, built in gubbins so they don't need external controllers and with heatsinks, not cheap Ebay.) although i do run them through RF remote dimmer modules. I also have DC-DC converters running TV, soundbar, laptop and high speed USB chargers. No interference on the radios.
 
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