L4 dimmer suggestions/critique wanted

Hi Folks,

There's been a lot done with dimming lights recently. The ARC4 is a great example of an excellent light that appears to be even more usable now that it can be dimmed way down for close-up work or extetended run time.

I've been successful with dimming the ARC LS using parts that only cost a buck or so. I was asked to see what could be done with the L4. I borrowed an L4 to see if there was a place to stuff a resistor in the tailcap.

So, what is this mystery part? What does it do and how does it allow an L4 to go from dim to bright?


It's a temporary variable dimmer made by simply removing one coil from a 500 ohm, 10 turn wirewound linear potentiometer. The pot I tore apart was NTE electronics #502-0102. Resistance from end to end is about 35 ohms. The pot can be ordered from sourceresearch.com

This coil has a bit of maksing tape wrapped around the wire near the lower end. The ends overlap on purpose. The coil is the same diameter as the end of the L4 battery tube. It works as a variabble resistor becasue one end is on top of the other. The battery tube touches the highest point first (about 30 ohms to the case, then progessivly more.

At some point the wire nearest the ends are touching, leaving near to 0 ohms.

I inserted the coil into the Z57 (??? the clickie) tailcap. It is capable of going from less than an ARC LS to what appears to be full L4.


Some possible improvements are:
1) Add soldered area to the ends for final low resistance contact.
2) Attach to some sort of carrier to ensure it's always in position.
3) Add some protection so that the grinding of the tube does not wear it out quickly.

Problems:
1) It flickers a little while turning, but not when the tailcap is sationary.
2) I'd like to see it get even dimmer.
3) It is not anchored.
4) I've only had it working for a few hours, so I don't know the lifespan.


I am hoping for suggestions and critiques. I'd love for someone to market such a beast if they can be made reliable.

Daniel

The idea of variable resistance by shorting coils is great. Don't know if it can be made reliable or not.

I have been thinking along the following lines.


There is a gap between the center plastic area of the z57 and the inside diameter of the l4 body before the step. The annulus gives about 0.050 inch to work with. So how about a coil spring that is just slightly bigger in diameter than the inside of the l4 body. The spring will be pushed in to the body up to the step and allow electrical contact. The spring extends slightly past the l4 body a tenth of an inch or so. Next take 4 surface mount resistors of about 80 ohms. (run them in parallel to make 20 ohms total) The resistors are soldered to the top of the spring 90 degrees apart. A thin washer is then soldered to the top of the resistors. This washer will contact the inside surface of the z57 clicky. So if the clicky is fully tightened the end of the body contacts the z57 like normal. Unscrew a turn or so, and the washer and resistors are still connected giving the dim. Unscrew more and the spring runs out of travel and the clicky is locked out.
Hope that explanation is not to confusing. I think something like this could be made to be reliable and would be simple to install. I havent looked for a spring yet, and have no access to surface mount resistors. Might have to order some next week to play.

Here is an attempt at an ascii drawing of it.

========= <--- washer
x...x...x <--- surface mount resistors
--------]
[-------] <--- spring
--------

Todd

ps. Daniel, I still haven't received the kroll mod you sent me, it must have gotten lost in the mail. /ubbthreads/images/graemlins/frown.gif

gaddjet: that is the neatest dimmer I have seen. I have a soft spot for continously variable dimming, and the turnable actuation is to my liking. The down side of the basic princapple is that you are degrading the efficiency by heating the resistor and lowering the input voltage to the converter.

That's a very good idea Todd. The amount of room inside the battery tube is sufficient for this to work. I like the fact that 1) it would not add extra pressure to the battery and 2) it would allow the tailcap to fully screw down.

BTW, your Kroll spring assembly has not been mailed yet... I ran out of 1/8 watt resistors and had to order some more so you, Klaus, Likebright, Mr Bulk and Nascar are all on the waiting list. I didn't want to send you one made with a surface mount resisitor unless I found a better way to assemble it. I hope to get the parts tomorrow so I can send them out.

Daniel

Ailsnail,

You are 100% correct. The resistor is not the most efficient way to do it... However, without it the L4 is using 10 times the power even if all you need are a few lumens to light a path.

The resistor is not very efficient, but I find that my arc LS will run for over 40 hours on "low beam" with a similar mod. It normally runs for 2 to 2 1/2 hours. similar run times should be possible with the L4.

Lights like the ARC4 will do MUCH better simply because they will keep the light at a steady output level (using PWM) while the battery runs down. If you set it for 10 limens you will get 10 lumens as long as the battery can supply the power. A simple resistor gives more light when the battery is fresh and less as the voltage drops.

Daniel

cool!

I also got some of this coil/wire from Daniel to play with and I have to say THAT I AM ABSOLUTELY IMPRESSED - my L4 got an instant variable dimmer function - this is f/&%$ing unbelievable. I will update this thread after some days/weeks of using the L4 this way.

The full Z57 functionality is still intact (Clickie and lock out) while adding the dimming function. If you start turning in from the LOTC positon and clicking it ON it starts at ARC AAA level and get subsequently brighter when turning further in until it reaches full brightness. You always can click the flashlight on/off and it will come on at the setting controlled by the in/out thread position. Very intuitiv to use and absolutely fool-proof so far.

I am using my L4 with a 17670 LiIon and using that cell the dimming range goes from full power to about ARC AAA level - I am using one ring of coil for it similar to Daniels initial post - using the standard 2 123 cell config one might need to use more coil or a higher resistance one to get such a very low setting like I am getting due to the higher voltage drop needed when using 2 123s vs my 1 LiIon.

/ubbthreads/images/graemlins/bowdown.gif @ Daniel & /ubbthreads/images/graemlins/thumbsup.gif

Klaus

I have a prototype of the l4 dimmer I posted about up and running. Still not reliable yet. It refuses to reset all the time. Might still work if I can make the right spring.

If you make one for my L4 I will buy it! Thanks either way...

Daniel,

May I step in line behind MR Bulk? I would gladly buy a dimmer for my L4 too.

You graciously sent me a dimmer for my Arc LS, and it works great. I believe an L4 dimmer would be even more useful.

Again, like MR Bulk, thanks in any event.

Paul

Daniel,

I know you are busy helping folks turn their Arc LSs into two level lights. I'm hoping that when that activity dies down a little you might be selling drop-ins for the L4.

Paul

I would take one also. /ubbthreads/images/graemlins/smile.gif
I LOVE this dimming stuff.

Me too!

Brightnorm

Yes, I'm keeping busy building mods for ARC LS's. I only expected a few people to want them. I've spent several hours a day (my free time) making and shipping them this week.

I did make my Streamlight TL-3 LED into a dual level light while waiting for some glue to dry. It was a simple tailcap mod. The same idea will probably work with the surefire clickie tailcap and lotc.

I'll look into it when I have some free time again.


Daniel

Now, now, let's not turn this into a "Paypal sent" type of thread, but keep it about the actual mod, ok?

(I'm in for one...ssshh)