Electrical resistance of Z57/L4 switch

PeterB

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I've observed on a nearly empty battery, that my L4 got brighter after fully depressing the switch (compared to the "Clicked on" position). I've measured the resistance with my Fluke, and I see a difference of about 0.2 Ohms between fully pressed and the permanent on position.

This resistance is more, than I would like! I use mostly a 17670 LiOn, this means I loose about 5% of the voltage and runtime.

Has anyone observed this behavior or found a fix?

ps: I've used Litfuse's washer trick to make the switch smoother. But I don't know if this behavior is related to this mod. I will try it also without the washer.
 

PeterB

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Ok, I found the reason /ubbthreads/images/graemlins/grin.gif and fixed it /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

If the button is not completely pressed, the current has to pass the inner spring of the switch. This spring has a small diameter and is relatively long (I think there are already some pictures posted) and has therefore a significant resistance.

I've shunted the spring with a very thin copper wire. The resistance of the clickie is now independent of the switch pressure. I also see an improved brightness with the empty battery.
 

PeterB

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I would like to add some pictures to describe the resistance problem of the Z57 and the solution better.

First a picture of my Z57 opening tool version:
faff86e9.jpg


There are many ways to open this clickie /ubbthreads/images/graemlins/grin.gif

This picture shows the upper and lower half of the clickie switch after opening it:
faff86e8.jpg


As you see, there is a tiny spring, which makes the connection and this spring has really a pretty high resistance (probably a steel alloy, small diameter, long lenght and the electons get dizzy with all the windings)!

The next picture shows the spring with my copper wire treatment to reduce the resistance:
faff86e6.jpg


After this change I observe a strongly improved performance with almost empty batteries! I think this mod gives a big benefit for all, using the KL4 in a 1 cell configuration. But also in a 2 cell configuration the runtime will increase (the electronic compensates the voltage drop with increased current consumption).
 

LitFuse

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Thanks for the pictures Peter. I have done some testing and discovered that the washer mod "fix" is likely to exacerbate this problem. I hadn't noticed it before due to the L4's regulation circuit masking the problem.


Peter
 

Ray_of_Light

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It is valid the suggestion, that I read in another thread, to put the Z57 in boiling water, and sealed in a ziplock, for ten minutes in order to soften the Locktite?

Regards

Anthony
 

LitFuse

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I've never used that same method, but yes, heating the switch will make it much easier to get apart. Some are *very* difficult to disassemble without heating.

Peter
 

PeterB

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I've only a single statistics, and mine was very easy to unscrew. I don't think that they used Locktite at all!
 

LitFuse

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Consider yourself lucky Peter. I've had a couple that I though someone at SF had used epoxy on, instead of locktite! Heating will make all the difference in the world.


Peter
 

Streak

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Thanks Peter and PeterB for all of your tips. In the not too distant future, I hope to be the first L4 owner in Africa!! Yes things take a little longer down here.

PeterB, dont you find that the with the wire wrapped around around the spring that its operation is affected?
 

PeterB

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Streak,

at the beginning this wire wrapping was only intended as analytical method, to see if this spring is the root cause and to measure the resistance change.
However I didn't observe any change of the mechanical switch operation => this will by also my final fix.
There is a lateral tolerance for the spring, and if the wire is thin and flexible enough, this seem to work very well.
But probably some guy will find a more elegant solution /ubbthreads/images/graemlins/smile.gif
 

LitFuse

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I just want to thank PeterB for figuring this out and sharing his very simple (though not very pretty /ubbthreads/images/graemlins/smile.gif ) fix with us. I performed 5 Z57 "washer" mods this afternoon and incorporated this "mod within a mod" on each of them. None of them show any excess resistance after re-assembly and testing. /ubbthreads/images/graemlins/grin.gif

This will become a standard part of the Z57 mods that I perform from now on. If I have performed a Z57 mod for you in the past (free or paid) I will update your switch with this refinement free of charge. Just PM or e-mail me and mail me your tailcap. I would like to thank PeterB and alanhuth for bringing this problem to my attention. I had not really noticed the problem because I primarily use the Z57 on an L4, which will mask the problem with it's regulator.


Peter
 

Darell

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LOCO is more like it.
Whoops! I found one of those springs almost folded double in one of my switches. The switch worked, mind you, but there's the spring with a huge left-turn in the middle of it. With all these great washer-finding tricks and all - does anybody have a source for a similar spring?

** I actually have the switch back together and working, so I guess it is a moot point. I'm just not sure what that spring is doing during compression. It can't be too happy when kinked like that. Hmm. Well, heck. This is fun. We're certainly learning more about these clickies, aren't we?

Sure do appreciate everybody's input on these!

Now, what am I gonna do with all these L4's that I've amassed? /ubbthreads/images/graemlins/smile.gif
 

FlashlightOCD

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[ QUOTE ]
Darell said:
does anybody have a source for a similar spring?


[/ QUOTE ]

A similar spring with less electrical resistance would be even better.
 

LitFuse

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[ QUOTE ]
FlashlightOCD said:
[ QUOTE ]
Darell said:
does anybody have a source for a similar spring?


[/ QUOTE ]

A similar spring with less electrical resistance would be even better.

[/ QUOTE ]

I've been looking for a while now. Haven't found anything even close yet though. Definitely not an "off the shelf" item. /ubbthreads/images/graemlins/frown.gif


Peter
 

Lighthouse

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Oct 1, 2002
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Hi guys,

Nice catch on the resistance of the spring. /ubbthreads/images/graemlins/thumbsup.gif

If someone wanted to take a few minutes to work on it, a similar but perhaps more elegant solution would be to take some coaxial cable copper braiding and solder it to an appropriate sized disk of brass or copper (or perhaps the end of the spring itself. Then have the slim copper braiding running through the center of the spring to the other end where it could be similarily attached. The spring may need to be compressed slightly to have working clearances. Suggest using a smaller soldering iron though.

Regards,
Lighthouse /ubbthreads/images/graemlins/wink2.gif
 
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