LEDs, Radio & EMI - Chevy Impala SS Forum
 
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post #1 of 4 (permalink) Old 08-05-2019, 08:22 AM Thread Starter
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LEDs, Radio & EMI

Yes, this will be about car audio. Yesterday while working on my garage I found a problem. I put an LED light under my wall cabinet and turned it on. Right away I got noise in my radio. I did some research last night on the problem. Most of the info concerned EMI in car audio systems with LED headlights. My question here is. If you've installed the LEDs in your car and you got the noise. What have you done to eliminate the problem? I'm looking for advance knowledge and the straight poop from those I trust the most, folks on here. Thanks all,

Mark: Snowman-33

93 9C1: Work & Cubic Ca$h This started with a new headlight and fender Celeritas In Conficiendo
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post #2 of 4 (permalink) Old 08-05-2019, 11:53 AM
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This is a basic/brief guide to LED operation. LEDs do not run on 12V. White LEDs usually around 4V. So for very small LED power loads a resistor reduces the voltage but produces a lot of waste heat. For a large LED load like a headlight a "switching power supply" is used. This means pulses of 12V is sent to the LED. This circuit switching on and off is what creates a wide band of radio noise that back flows through the 12V car system to the radio. If it is really bad it makes it to the car antenna.(like your shop light)



A well designed "switching power supply" includes chokes/coils/filters that dampen out it's noise. All metal construction around the"switching power supply" also reduces the noise.


As the "switching power supply" can be built to run at any frequency depending on circuit design and what parts are cheap a aftermarket filter can be a " hit or miss" fix. Most filters are tuned to one frequency and get expensive if they really work on any frequency.
I would suggest you look to reviews and ask around for your best choice.



DOT in USA and Canada do not allow the replacement of a light bulb in a lens with a different light source(bulb#, HID, or LED) without retesting and certification. So most aftermarket LEDs are not legal in north america for on road use.


Bottom line is if the LED light source is not in the exact same place as the bulb filament the light focuses differently. You may like this but on coming traffic on unlighted roads will curse you. It will change the height of the cut off point and the width of the beam.

Z09B4U

Last edited by Z09B4U; 08-05-2019 at 11:57 AM.
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post #3 of 4 (permalink) Old 08-06-2019, 05:06 AM Thread Starter
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Z Thanks for your info here. I didn't know about the voltage and frequency differences. Kinda interesting. I've done some research and and now know what those things are on different electrical items are. The round deals on electronic power cords, Ferret Beads. If it weren't for the work I'm doing on my garage right now, I would most likely be nerding the web more about this. The garage is not quite square. I'm wanting to get it finished before I'm eligible for Medicare this month. Thanks again my Friend,

Mark: Snowman-33

93 9C1: Work & Cubic Ca$h This started with a new headlight and fender Celeritas In Conficiendo
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post #4 of 4 (permalink) Old 08-06-2019, 10:33 AM
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Switching power supplies have been around forever. But they have made great advancements. They can achieve over 90% efficiency. Power transformers must use AC. and produce waste heat. The transformer required to run a modern laptop would weigh more than the laptop. What would be required to run a desk top computer would be very ugly and hot. Switching supplies are in a lot of things around you. A smart phone car charger is a common example. Use 1970's solid state technology and it would waste more energy than a brake light uses.



In areas where winter includes real snow LED's have another issue. Since they produce light with much less heat they will get covered in snow or iced over. As I have been out in weather where normal head lights ice over, LED, or HID(low heat too) are not a good choice for me.



My understanding is that LED traffic lights can be obtained with defroster lenses for area's that are prone to snow them over.

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