How bad is RFI from LEDs? - Page 1
Forum section: electronics / beginners

author: KateCool
author_rank: Newbie
timestamp: November 02, 2022, 12:23:29 pm
content: I am sick and tired of my old halogen headlights, and I want to convert to LEDs. The charts say I totally canhttps://lightninglab.org/dodge/dart/2013/. But the more I research them, the more I am... confused?So, basic issues aside, there is another thing. I recently discovered that LEDs can produceRF interference. What should I make out of it? Is it really bad?All I could find is even more confusing. Some people find it, and some don't. One guy said it was bad and then it subsided and stopped altogether. I am not sure that is how it works, honestly.So, any advice is welcome. I just want to know how that will influence me if I convert and the LEDs will produce RFI

author: TopQuark
author_rank: Frequent Contributor
timestamp: November 02, 2022, 12:34:56 pm
content: LEDs themselves don't create EMI, crappy LED drivers do. I used to have a couple of LED panels powered by cheap chinese drivers, which were nasty flybacks with the cheapest of components. The LED panels themselves were aluminium PCBs and weren't earthed. What ended up happening was, the panels acted as one plate of a capacitor, and coupled common mode energy to every conductive thing on my table underneath, including the ESD mat.I never realised it was a problem until I was working on a sensitive battery powered circuit (floating), and I kept picking up noise whenever I was probing it with my scope (earthed). Took me some time to realise what was the culprit.Long story short, if you are going to use LEDs, don't cheap out on the drivers, otherwise you will hate yourself.

author: Kleinstein
author_rank: Super Contributor
timestamp: November 02, 2022, 12:42:02 pm
content: The LEDs itself don't produce RFI. The LEDs run best from DC current and need some extra circuitry to control the current, like drive them with a constant current. There are different types of drive circuits and some of them can produce RFI, while others don't produce noticable RFI, but possibly a not that good power factor. AFAIK the combination of seprate LED driver and LED panel is often one of the more problematic ones. Cheap bulb replacements can be OK (may still have a not that great power factor, but still not bad).With normal levels humans don't react to radio frequencies. So nothing to worry from that side. RFI can however interfere with some sensitive electronic parts. Often it takes LED lamps that emitter more than allowed and especially sensitive target circuit to come together to cause a problem. If both sides are within the legal limits there should be no problem.

author: radiolistener
author_rank: Super Contributor
timestamp: November 02, 2022, 02:38:00 pm
content: Quote from: KateCool on November 02, 2022, 12:23:29 pmyes, LED lamps produce RFI, because they using switching mode power regulator. But you can expect moderate level of RFI if you buy a good quality LED produced by branded manufacturer.You can eliminate RFI noise if you remove it's driver and power it from a linear power supply. But linear PSU will be very inefficient in comparison with switching mode PSU.

author: Grandchuck
author_rank: Super Contributor
timestamp: November 02, 2022, 03:08:36 pm
content: There are products sold to eliminate headlight noise:https://chromeglow.com/products/emi-led-headlight-noise-eliminator-filter

author: tunk
author_rank: Super Contributor
timestamp: November 02, 2022, 04:19:42 pm
content: Quote from: edavid on November 02, 2022, 02:50:48 pmI guess it depends on the bulb. True if it's a resistor in serieswith LED(s) or a linear regulator. Maybe not if it uses a switchingstep down converter.

author: RoGeorge
author_rank: Super Contributor
timestamp: November 02, 2022, 04:26:17 pm
content: LEDs are more economical, but in terms on quality of the light, they are "good enough" at most, while halogen lights are great in terms of light spectrum, intensity and colors rendering, as long as you can afford the electricity bill.To put it blunt, when switching from halogen to LEDs, even the very good LEDs look lame. Not to say the range of problems from low end LEDs, like RF interference, flickering, bad spectrum, short life, etc.

author: mikerj
author_rank: Super Contributor
timestamp: November 02, 2022, 08:31:39 pm
content: Quote from: edavid on November 02, 2022, 05:20:55 pmAgain, the OP is asking aboutLEDheadlights for his car. These use high power LEDs that are invariably driven by some kind of switching current regulator rather than a simple crappy current limiting resistor.

author: TimFox
author_rank: Super Contributor
timestamp: November 02, 2022, 08:35:39 pm
content: Not about automotive lights:Unfortunately, my nice modern workbench lamp with LEDs is on the end of the workbench next to the inputs of my spectrum analyzer and THC analyzer, on a shelf next to the bench.The effect is very noticeable.I still have an incandescent bulb in the bench lamp on the other end of the workbench.

author: james_s
author_rank: Super Contributor
timestamp: November 02, 2022, 08:39:32 pm
content: RFI is certainly possible, all LED headlights to my knowledge use a switching regulator.A bigger issue is that at least the last time I checked, there are no legal LED retrofit bulbs for car headlights. If you look closely, the bulbs will be labeled for off road use only, and if you install them in optics meant for halogen bulbs the beam pattern will not be correct and it will make a lot of glare. If you want LED, you have to replace the whole lamp assembly.

author: SmallCog
author_rank: Frequent Contributor
timestamp: November 02, 2022, 08:56:23 pm
content: Find somebody that has LED headlights and go for a drive with them at night, see if you actually like them.I have an LED light bar on one of our vehicles and whilst it makes a ridiculous amount of light, it's not a nice light to drive with due to its poor CRI

author: RJSV
author_rank: Super Contributor
timestamp: November 02, 2022, 10:15:20 pm
content: Get the right controller situation.If you've seen those department store garden lights they typically almost always use a crude FLYBACK style interrupted coil to generate a couple volts, on a lesser output solar cell output, (charging am AAA battery). So, that means 233 khz square wave, whenever the little LED light is on, in a dark night.Even worse, some have a 'cord' acts as antenna although that's a bit of extra info.

author: james_s
author_rank: Super Contributor
timestamp: November 02, 2022, 10:33:28 pm
content: Quote from: SmallCog on November 02, 2022, 08:56:23 pmWhat matters more than that is other drivers. You'd see great with a set of rally style driving lights, but other drivers would be blinded. That's the biggest problem with aftermarket headlight retrofits.

author: SmallCog
author_rank: Frequent Contributor
timestamp: November 02, 2022, 11:10:50 pm
content: Quote from: james_s on November 02, 2022, 10:33:28 pmYes and no...I can drive all night and not see another vehicle here in Australia. In fact I could probably drive for a week and not see another vehicle... so my "rally style" driving lights don't really affect anyoneHowever even with factory fitted LED lights that don't throw off glare the CRI makes the LED lights crappy in my opinion.Good light is more useful than lots of light.That said I can't stand poorly adjusted glary headlights, which are unfortunately typical of HID or LED conversions of incandescent housings.

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2022, 12:26:53 am
content: Well if you live in a rural area then obviously there are different constraints, but I would still argue that it is better to add additional driving lights and maintain low (dipped) beams that are appropriate for driving around other cars than it is to put incorrect retrofit bulbs in your regular headlamps.I do agree about the importance of CRI.

author: KateCool
author_rank: Newbie
timestamp: November 03, 2022, 11:07:33 am
content: Wow, thank you, everyone! That is a lot to think about. Guess it is better for me personally to replace them with brighter halogens.Would have never figured that out without your help

author: james_s
author_rank: Super Contributor
timestamp: November 03, 2022, 05:44:36 pm
content: Check the condition of your reflectors and lenses, that can make a big difference in light output. Some cars have inadequate wiring resulting in lower voltage to the bulbs, some people add relays with heavier wires. Crappy plastic reflectors deteriorate and that causes a large drop in light output.

author: SmallCog
author_rank: Frequent Contributor
timestamp: November 04, 2022, 12:23:18 am
content: If your vehicle has plastic lenses that have weathered and become opaque you can get them nice and clear again with a bit of normal car polish, preferably something with a strong cutting actionOnce the UV resistant layer weathers off this will happen pretty regularly. regularly wiping them over with a product like 303mayslow this down

author: EPAIII
author_rank: Super Contributor
timestamp: November 04, 2022, 07:47:58 am
content: Tell me about it!Quote from: james_s on November 02, 2022, 10:33:28 pm

author: hneve
author_rank: Regular Contributor
timestamp: January 23, 2024, 03:20:51 pm
content: I was also curious about the radio interference thing with LED headlights. It depends on how good the LED lights are. The better ones usually don't cause much trouble with radio signals because they're well-shielded. Most of the time, you won't notice any issues with your car's radio or electronics.But, if you go for cheaper LED lights, they might not be shielded either, and that's when you could get some interference. The idea of the interference going away alone doesn't make sense. If there's an issue, it usually stays until you fix or change the lights.I found out a lot about this onleds.to. They have a bunch of information about LED lights, including how they can mess with radio signals and what you can do to avoid it. Their advice helped me understand what kind of LED lights to choose and what to expect with radio interference.

author: Faranight
author_rank: Unknown
timestamp: January 23, 2024, 03:27:55 pm
content: Umm, hneve, this thread seems to be more than a year old. Also, there was another thread about this topic recently:https://www.eevblog.com/forum/projects/electrical-noise-free-led-workbench-lighting/