Help: Interior LED Light Bar emitting high pitched noise.

Thread Starter

mtdavis53

Joined Apr 10, 2018
1
Hello everybody,

First time user seeking advice/help.

I purchased in the past few months a Visor Mounted LED Interior Light Bar (for law enforcement use) from a retail company.
Listed Price: $499.96
Sale Price: $249.96
Powered by the standard 12v cigarette lighter plug.

First let me say this light bar is of decent quality, minus one MAJOR FLAW. The lights are bright, the patterns are sufficient. I like the product based on the light that is emitted from the product. However:

The light bar since receiving the item while being powered on makes an audible high pitched wailing noise that is quite noticeable (whether on steady burn or flash patterns.) Within minutes I have had other Officer sitting in my vehicle state they have had to "get out" because that noise is headache inducing and incredibly annoying. Myself, like all the other officer's who had heard the light bar clearing believe that there is a defect/malfunction with the light bar, because none of them have ever heard a light bar make any noise let alone a high pitch wailing.

I sent the product back to the company/manufacturer after their approval from submitting evidence of the noise for a warranty repair. Exact words taken off their webpage.
"5 Year Limited Warranty on All LED’s that are used in our products including all products for sale that use LED’s.
2 Year Limited Warranty on All Components. Components include but are limited to Switches Boxes, Brackets, Housing units of the items and Internal Components."

After receiving the item the official response for the company when I received a phone call has been:

"The audible high pitch noise emitting from the light bar is normal and expected. I have also been the first/few people to file a complaint about the noise. After speaking to the manufacturer directly the also confirmed that the noise is normal. No repair is required as the light bar is functioning as expected. There is no defect in our product."

I find this response extremely hard to believe having been around hundreds of police issued LED's and light bars during my time as a Police Officer I have never once heard any noise being emitted from the LED's. Also, if nobody is complaining about a high pitched noise how is mine making one "normal. When I stated, to please fix the noise they stated their was nothing to fix. When I then asked for a refund on the product due to a LED Lightbar emitting audible noise which i believe to be a malfunctioning product I was told a refund WILL NOT be issued due to the product being in my possession for longer than 30 days.

My question is to you more technical savvy/electronic knowledgeable individuals is this noise truly "normal and expected." Why have i never heard it from hundreds of other lightbars I have been around. Due to the company's refusal to do anything. I am under the impression the product will be shipped back to me today "as is". How can I fix the product so that this noise stops?

Also see video attached demonstrating the audible noise. It is quite impossible to sit inside a quiet vehicle listening to that noise for hours on end while working secondary employment.


Thank you and apologies for the wall of text. I wished to be detailed.
 

KJ6EAD

Joined Apr 30, 2011
1,581
The Texas Instruments document above, SLUA821, has some accessible information on page 4. If you open the housing exposing the circuit board, post a clear picture of it.
 

wayneh

Joined Sep 9, 2010
17,167
.
My question is to you more technical savvy/electronic knowledgeable individuals is this noise truly "normal and expected."
I might accept “not completely surprising“ but it’s not normal. There’s probably an oscillator used and oscillating current can create mechanical motion that results in audible noise. My kids complain about the high pitched noise one of my TVs makes. I can’t hear it. Anyway, I think attention to this issue at the design phase can avoid the problem.
 

MisterBill2

Joined Jan 23, 2018
12,395
Since it is an LED light bar the problem is not the power oscillator for the flash tubes, but rather the transformer or inductor in the switching regulator for the LED devices. But it might also be microphonic capacitors, since both sources are known. While some sound at some level may be normal for that manufacturer, it is an indication of a part that is not "OK", and will fail sooner than later because of the vibration. If you are competent to open the light bar housing to expose the electronics portion without damaging it, then there are potential fixes available. If you are not competent to do that then please find somebody who is, such as perhaps the folks who add the police electrical stuff to the vehicles.
Noisy disc capacitors can often be quieted by the application of some electrical grade silicone adhesive/sealer. The same material can also be applied to noisy transformer cores, which are the usual guilty devices. It is important to use the variety of silicone that does not involve acetic acid in the curing process because the acid is corrosive to the electronics and wiring. Adding the silicone is often done, so while it seems a radical approach, even some military electronics has it.
 
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