Just got my Fenix L2D Q5

TexLite

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The noise is most probably coming from the tailcap,Fenix does pot their inductors with red goo.I have never had one hum in the head,but I have had different ones squeal in the tailcap.Probably poor contact.

I was trying different tailcaps on an L1T v2.0 modded with XRE R2 and RV7 driver,a v1 forward clickie was the worst,I dont think the tailcap would have lived long in that application.The RV7 driver can pull close to 3amps from a NiMH,which exagggerates any weakness in the switch.On turbo you are probably putting around 1.3 0r 1.4 amps through the switch,which shouldn't be a problem.I would make sure my connections were tight and watch closely for any flicker.If you have any deoxit/progold take the cap apart and put in a couple of drops.

On that L1T/R2/RV7 I currently have a switch modded with solder wick that is performing well so far,its a real screamer for 1AA.Some of the switches I have opened up have been VERY poorly centered,they have required de-soldering,breaking the thermal adhesive,then recentering.YMMV.

You cant go wrong with the Eneloop's,you might be able to pick up the four pack with charger up at Wallyworld.

Michael
 

Marduke

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The noise is most probably coming from the tailcap,Fenix does pot their inductors with red goo.I have never had one hum in the head,but I have had different ones squeal in the tailcap.Probably poor contact.

I was trying different tailcaps on an L1T v2.0 modded with XRE R2 and RV7 driver,a v1 forward clickie was the worst,I dont think the tailcap would have lived long in that application.The RV7 driver can pull close to 3amps from a NiMH,which exagggerates any weakness in the switch.On turbo you are probably putting around 1.3 0r 1.4 amps through the switch,which shouldn't be a problem.I would make sure my connections were tight and watch closely for any flicker.If you have any deoxit/progold take the cap apart and put in a couple of drops.

On that L1T/R2/RV7 I currently have a switch modded with solder wick that is performing well so far,its a real screamer for 1AA.Some of the switches I have opened up have been VERY poorly centered,they have required de-soldering,breaking the thermal adhesive,then recentering.YMMV.

You cant go wrong with the Eneloop's,you might be able to pick up the four pack with charger up at Wallyworld.

Michael


Remove the switch entirely and short the back end. Listen what happens to the noise then. I bet it gets much louder. It's not the tailcap making the noise, it's just the easiest place to hear it.
 

Gunner12

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Only the LOD uses PWM for constant on modes (others use only for strobe and SOS)

That's what I though, though I wanted to make sure.

Maybe you light isn't as well potted or the potting compound isn't placed in the right place.
 

tennisplyr3

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So what is the problem -- if there is any at all? Is it the batteries? Or is it the circuitry? Or is it a poor contact problem? Possibly oxidation? It's completely new.
 

TexLite

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Remove the switch entirely and short the back end. Listen what happens to the noise then. I bet it gets much louder. It's not the tailcap making the noise, it's just the easiest place to hear it.

With the tailcap removed I dont get any noise,nor do I get any with a switch modded to a twisty.

Some switches are worse than others,with my current switch I dont any noise.

Yours may come from the head,but I'm sure mine was the switch.

As Gunner12 said,yours may not be potted well,you can always open it up and see if its bothersome.

Michael
 

TexLite

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So what is the problem -- if there is any at all? Is it the batteries? Or is it the circuitry? Or is it a poor contact problem? Possibly oxidation? It's completely new.

My guess is the switch,I can loan you a switch to try,if you want to pay for sending it back to me.If it still makes a noise,the it is as Marduke said,in the head.

Michael
 

R-R

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Just for statistics/ref purposes, I have the new L1D-CE Q5 (see sig) and with the L2D body and Lithium AAs it does make a noise.
(on turbo i think? I'd have to retest this as i have mostly only used it in L1D mode till now)...

Oh well ! :)
 

tennisplyr3

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My guess is the switch,I can loan you a switch to try,if you want to pay for sending it back to me.If it still makes a noise,the it is as Marduke said,in the head.

Michael

Oh, that won't be necessary. Thanks for your offer though! I have already contacted Fenix about it. I'm waiting to see what they have to say about it... :thinking:

I didn't know that they used inductors in flashlights. I know how they're used in signal filtering, but I wasn't aware of their applications in flashlights. Why would they give a high frequency whining sound though?
 

Marduke

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Oh, that won't be necessary. Thanks for your offer though! I have already contacted Fenix about it. I'm waiting to see what they have to say about it... :thinking:

I didn't know that they used inductors in flashlights. I know how they're used in signal filtering, but I wasn't aware of their applications in flashlights. Why would they give a high frequency whining sound though?

Inductors are used to boost the voltage. High power LED flashlights in general squeeze lots of electronics into the head to control and regulate the output. It is extremely common for these circuits to make audible noise which can be heard with young ears.
 

tennisplyr3

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Inductors are used to boost the voltage. High power LED flashlights in general squeeze lots of electronics into the head to control and regulate the output. It is extremely common for these circuits to make audible noise which can be heard with young ears.

I just got a reply from the Fenix-Store. The person said that it is completely normal and is coming from the circuitry from the head. I don't think I have that good of ears either -- I can't hear anything past 17kHz. I was just wondering what was the physics behind the sound... any takers? Haha...
 

Jarl

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It's not a high pitched whine on mine so there's no reason old people couldn't hear it. Also, it comes and goes- currently gone.
 

cdosrun

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I just got a reply from the Fenix-Store. The person said that it is completely normal and is coming from the circuitry from the head. I don't think I have that good of ears either -- I can't hear anything past 17kHz. I was just wondering what was the physics behind the sound... any takers? Haha...

Hi TennisPlyr,

boost regulators use the back EMF of an inductor to increase the voltage of the output with respect to the input (I'm not brilliant about the intricacies of the designs), a MOSFET switches the votage into the inductor at a higher current than the output due to the voltage gain (Pin > Pout but the efficiency is usually quite high ~90ish%).

Sudden rushes of high current into an electromagnetic device can cause magnetostriction whereby the stampings and coils can resonate which is coupled to the air and you can hear it. I have made an audio amplifier that can be heard when powering a dummy load because the transistors exhibit this effect and 'sing' with the music. As mentioned earlier, some manufacturers pot their components in epoxy which usually dampens magnetostriction to the point that it can't be heard.

I have pretty good hearing but most of my torches are quiet at the head-end, it is only the arcing in tail cap switch I can hear (most notably in the Nitecore DI).

You might get some more clued up individuals to give a better description on a boost regulator in a minute!

Andrew
 

tennisplyr3

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Thanks for the explanation. I guess the resonance makes sense, but I'm not that motivated to look into it. Haha...
 

HKJ

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I did some measurements on a L2D and a P2D flashlight.

They are using a switching frequency around 400Khz, i.e. well outside the audible range.
But in some cases a secondary frequency shows up, probably due to some regulation and it is well within the audible range (800 Hz in this case).
The sound can then be made by the wires on the inductor, or by some other magnetic metal close to the inductor (if any exists).

Here are the scope trace of the current consumption, showing the frequencies.

First the L2D with a slow time, it is very stable, no audible sounds possible:
L2D%20High%201.PNG


To see what the thick line consists of, I have increased the speed (It is a 400Khz switcher):
L2D%20high%202.PNG


And the same for P2D, first the slow trace, here is a very visible 800 hz frequency:
P2D%20high%201.png


And a fast trace with P2D, here the switcher is a bit unstable.
P2D%20high%202.png
 

tennisplyr3

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Ok, erm, that was unexpected... I just put in another set of older rechargeable batteries into my light (same model and make), and it stopped whining in turbo mode. I can still hear it slightly in strobe mode, though.
 

Mugrunty

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Just a slight Idea/theory. I'm willing to bet that only the Cree type lights make the buzzing noise. It's just that I used to have a L2D 135 lumens using a cree LED. It was one of the older ones, but I lost it at college.:banghead::mecry: Anyway, I remember it making the noise you're talking about but only in turbo mode. Well I was so sad, that I bought a new Rebel 100 premium L2D. Um, this light never makes the buzzing noise in turbo. Funny. Anyone else have a Rebel100 L2D to test for the no buzz noise???
I also remember the Cree getting a lot warmer then my Rebel, even thought the rebel is brighter.
 

Marduke

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Just a slight Idea/theory. I'm willing to bet that only the Cree type lights make the buzzing noise. It's just that I used to have a L2D 135 lumens using a cree LED. It was one of the older ones, but I lost it at college.:banghead::mecry: Anyway, I remember it making the noise you're talking about but only in turbo mode. Well I was so sad, that I bought a new Rebel 100 premium L2D. Um, this light never makes the buzzing noise in turbo. Funny. Anyone else have a Rebel100 L2D to test for the no buzz noise???
I also remember the Cree getting a lot warmer then my Rebel, even thought the rebel is brighter.

It's the circuit, not the LED. All electronics can buzz/whine/squeal. My worst light for it is the first 5 seconds of startup for a 2D MagLED.
 
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