preon 2 problem

[Jmora]

I've been using my preon 2 for about 4 months now, pretty heavily in fact, as I am in a place where there is very limited electricity and nightly blackouts. In the last 2 weeks the preon has been playing up, when I click it on it frequently fails to switch on properly, or only flashes. I have to tighten or loosen the screw around the button and then it seems to work again. Still its annoying and shouldn't have these issues. I have tried to remedy it by taking it apart and rescrewing it together again, but that doesn't seem to work. Obviously I have tried new batteries as well, to see if the problem was there.
another problem that arose concurrently is that on certain light intensity modes there will be a high pitched electronic whine, usually on medium mode. I don't know if this is an extra clue as to what is the problem.
Any help would be appreciated, I am jealous of my friend's 5 euro chinese flashlight that does not exhibit any of these problems 

[Heinz Doofenshmirtz]

To my knowledge, the switch issues is a separate (and old one) issue from the inductor whine problem.

I have an HCRI P2 that is my primary EDC torch, and while I haven't had any whine problems (at least that I've been able to hear), I have the same switch issue.

There was a thread over at CPF about a year ago posted by someone who did some modding on his Preon switch that pretty much just completely removed the solid cap on top of the switch.  I personally don't want to go that far. 

As far as I can tell, the switch problem is caused by that little round plate getting sideways in the switch housing and binding up.  My solution so far has been to take the threaded cap off, remove the solid piece under it, and clean them all thoroughly with some alcohol and a q-tip.  Then I put a pinch of graphite under the solid piece, and put it back on with the threaded ring.  It's worked pretty well for me so far, but every so often I have to put a bit more graphite in it, and go through a day or two of getting it on my hands, etc.  But otherwise, it seems to work pretty well for the most part.

[Jmora]

thanks for the answer  , it makes sense, because there does seem to be some grit in switch somewhere. I'll try cleaning it as soon as I get access to some alcohol and q-tips.
So the whine is from the inductor? could you explain this more (including what an inductor is  )? I assumed that something was loose in hte mechanism and was resonating.

[Heinz Doofenshmirtz]

thanks for the answer  , it makes sense, because there does seem to be some grit in switch somewhere. I'll try cleaning it as soon as I get access to some alcohol and q-tips.
So the whine is from the inductor? could you explain this more (including what an inductor is  )? I assumed that something was loose in hte mechanism and was resonating.

I'm no electrical engineer; I don't know if it's a capacitor, a resistor, or some other part or arrangement of parts, so someone else can probably explain it better than I can.  But, all modern LED flashlights have a circuit board in them with some parts that supply a constant amount of current to the LED.  This is typical for regulated lights; 'regulated' simply means they don't dim as the charge level of the battery reduces through use.  The inductor is part of the regulation circuit, IIRC, that supplies that constant level of voltage to the LED.  For some reason they whine sometimes. 

I've read about this on CPF and it seems to be an issue with 4Sevens lights in particular; that might just be sampling bias though, as gear/torch/MT aficionados tend to be a lot more picky about stuff like that.  I've had close to a dozen 4Sevens lights in the last few years, and never had the problem with any of them.  You might want to email them as ask about warranty or replacement of it.

[tattoosteve99]

I have a custom led in my mag lite and it has a electronic whine to it also. It's usually ,I think, coming from the circuit board as it converts the power.

[gustophersmob]

Heinz gave a good overview of how the regulator functions.  Since I am an electrical engineer, I thought I'd add to it a bit, although I haven't seen any schematics of a light's regulator circuit, so don't take this as gospel

I'm assuming they are using a switching regulator to generate the necessary voltage to meet the Vf of the LED (typically ~3.5V).  In plain English, they use a circuit to increase/decrease the voltage from the battery (any where from ~1.2V to ~4V) to the voltage necessary to make the LED turn on.

Switching regulators use an inductor to "smooth" the current, much like an AC supply uses capacitors to "smooth" the voltage.  Basically, an inductor looks like an open circuit to certain AC frequencies, much like a capacitor looks like an open circuit to DC voltages. That blocking from the inductor is what smooths out the current.

Basically, all an inductor is is a coil of wire.  The number of turns and the diameter of the coil determine the frequency range which it operates at (along with other circuitry components and tuning coils, etc). Typically what causes an inductor to whine is when the coils of wire happen to be the right diameter and shape so that they resonate mechanically at the same frequency the inductor is tuned to.  The smaller the physical coils of wire, the higher the resonant frequency.

Hopefully all that made sense and wasn't too much uber-geek!   

[enki_ck]

I hope this isn't a sound of bad things to come but I had two flashlights with inductor whine issues so far. An itp A2 and a Fenix LD01. They both later developed contact issues and died. I sent the itp back and got it fixed but the Fenix is no longer covered by warranty. I can sometimes still get it to work but I don't trust it. If I remember correctly you were saying something about going to Africa some time ago. If you're moving around a lot sending something of for warranty isn't a good idea. Do you have some kind of a backup flaashlight just in case?   

[Jmora]

thanks for the information on inductors,  , I've actually almost finished my time in Africa, so it lasted this far, I have my arc AAA light as backup and it is always very reliable. if the whine issue is only an idiosyncracy, I can deal with it, but if it really suggests a growing problem, I'll have to see if I can return it. I might ask the 4sevens people what they think.

[Heinz Doofenshmirtz]

gustophersmob, thanks for the extra info!    I didn't know an inductor was actually a kind of field coil.  Is that how it was actually conceived/designed?  Or, is it just how it happened to work out to provide the necessary 'smoothing' of the current?

Jmora; I wouldn't worry about it too much.  Unless it becomes really noticeable, I doubt it would be much of a problem.  Even if it does cause some kind of failure, 4Sevens is usually pretty good about warranty issues.

I'd recommend that once you get some alcohol and q-tips, disassemble it into its three main pieces, head, body, and tail-cap, and give all the threads and the contacts inside the head a good cleaning.  Also, make sure to clean out the inside of the threads in the tail-cap, and the flat ends of the body as well.  I've found this is important because occasionally when switching between my P1 and P2 bodies, a bit of the lube I use on the threads can get onto one of the ends of the body and prevent the light from turning on. 

Once you've cleaned it all up, if you can get any, Nyo-gel is the best lube to use for flashlights, and a thin layer on the threads will help with water resistance as well as provide lubrication.  I also try to be careful and not get any graphite into the lube either.  I don't think it might be a serious problem, but I suppose it could cause the Nyo-gel to dry out and lose its effectiveness, and the graphite might interfere with the current between the head and body.  But, I honestly don't know. 

[Syph007]

Basically, all an inductor is is a coil of wire.  The number of turns and the diameter of the coil determine the frequency range which it operates at (along with other circuitry components and tuning coils, etc). Typically what causes an inductor to whine is when the coils of wire happen to be the right diameter and shape so that they resonate mechanically at the same frequency the inductor is tuned to.  The smaller the physical coils of wire, the higher the resonant frequency.

Hopefully all that made sense and wasn't too much uber-geek!   

Oh.. so its a mechanical resonance.. interesting.  Can that be solved by potting the electronics or would they still move enough to make noise?

[gustophersmob]

gustophersmob, thanks for the extra info!    I didn't know an inductor was actually a kind of field coil.  Is that how it was actually conceived/designed?  Or, is it just how it happened to work out to provide the necessary 'smoothing' of the current?

Heinz, they are similar and different, both operating based on the principles of electromagnetism, but applied differently. Hopefully I can explain in a somewhat clear way.

Inductors typically are used to take advantage of the ability to store energy in the magnetic field that is generated when current is passed through the coils of wire. 

Field coils are also coils of wire, but are typically designed and used in applications that take advantage of the electromagnetic field itself.  These can use either DC or AC and are typically parts of motors or generators.  Whether it is DC or AC dictates the way the field coil is designed and effects many things.  At its most basic, a DC field coil generates a stable magnetic field of constant intensity (since the wire coil acts as a short to DC).  AC gets more complicated since the inductive effect of the wire coil comes into play, as well as the alternating current direction.  Most common AC motors are 3-phase, and get somewhat complicated theoretically.  Unfortunately it has been too many years since I have studied electric motor theory, so I will have to brush up on them in order go any more in-depth.

Actually, the wikipedia page on inductors is quite good and give a lot more in-depth understanding than what I have provided.

Oh.. so its a mechanical resonance.. interesting.  Can that be solved by potting the electronics or would they still move enough to make noise?

My experience with inductor whine in other applications has always been due to mechanical resonance.  I think this would be especially true in such low power applications like a flashlight's regulator circuit.

I think potting should stop it.  Really, any physical change should be enough to stop the whine on a small coil at high frequencies (IIRC, I've read somewhere that typical flashlight regulation circuits operate around 2-3kHz), so even a slight bending of one of the coils might solve it. Conversely, if it is potted and it whines, de-potting it should change the resonance enough to make it stop.

[Jmora]

lots of interesting info on this thread 
@Heinz, I'll try out your maintenance suggestions as soon as I am back home.

[Heinz Doofenshmirtz]

lots of interesting info on this thread 
@Heinz, I'll try out your maintenance suggestions as soon as I am back home.

Just reading through some old threads today... any news on your light?

Hey Gustophersmob... if we could find some financial backing, we could start our own torch company... perhaps it's just my personal bias, but I think with a collaboration between an electrical engineer and a perceptual psychologist, we could design some pretty darn cool lights!

Ah, who am I kidding...   I have so much other stuff to deal with as it is!   

[Jmora]

Well, I am back home, but haven't got around to cleaning the preon yet, I really ought to. The thing is, I have unscrewed it a few times, and wiped the accumulated grit out of it just with the fingers, now it seems to work just fine. Having said that, I don't use it everyday like I did in Africa, so maybe its just not being used as hard. I opened up my computer today to change the RAM, and it had a lot of red african dust in it too.