ARC-AAA with 8mm white led (with pics)

I may say that this is my "serious" first mod if I don't count a kiddy Solitaire mod and making a few new ARC-AAA heads with different leds. However, I can't say it is a "real" mod, it is more of a "frankenstein" style.

Though I planned to do ARC-AA with Luxeon mod, I wanted to try a cheaper one as a practice - 8mm white led from ISP (16000mcd) on ARC-AAA head from dpr.

Sorry for the poor focus of the pictures, someday I hope to buy a better camera.

First, I had to widen the hole to fit the 8mm. Left is normal ARC-AAA head and right is 8mm hole in it. I polished the reflector, but it gives no difference to the beam.



Initially I wanted to use a regulator IC "MAX1797" from Maxim. They were generous to send 2 pieces for evaluation. It claimed to have over 95% efficiency and max 500mA. From the data sheet, I expected at least 200mA 5.0V output or 400mA 3.3V output with 1.5V battery voltage. Sounds very promising.

Test result was quite poor. Of course with long cables on the spider web, it would be wrong to expect something very good, but it failed to deliver more than 30mA to led from 1.5V input (both 3.3V and 5V output).

So I decided to stick it to Micro Converter from Sandwich Shoppe. It claimed to be current regulated and pump out 155mA from 1.2-1.6V input.



Again, I was quite dissapointed to find out that it only delivered about 80mA current to led (I tried 8mm and a Luxeon) from a fresh AA battery.

Anyone know what could be wrong, or is it supposed to give this much only? Or is there a way to pump more current to led?

After inserting the led to the head, I pushed in some silicon sealant hoping to make it a water proof. I didn't want to use epoxy since I may take the converter for other mod later. I didn't put it in the water, but the blow and suck test shows it is not waterproof, sigh!

Then the covnerter goes in, the head is done. I later pushed in the led a bit back to the head to reduce the light spill from the led.



Because the diameter of Micro Converter is a little smaller than ARC-AAA board, it moved to the size and also easily short the batter-in or led-out with ground on the head aluminum.

So I added a short wire along the edge of the board to make it a tight fit to the head and adjusted it to touch the battery positive contact only when the head is fully turned in to prevent the further turning in to cause shorting.

Drop battery, screw in, here it goes! The blank head I used is not anodized (?), so it is lighter color.



Beam shot at 1m distance from the wall. Left is ARC-AAA-P and right is ARC-AAA-8mm, both with fresh alkaline batteries.



This 8mm white led has 55 degree viewing angle and barely gives any spill. Compared to ARC-AAA-P beam, the overall corona size is smaller, but it has a bigger and tighter hotspot.

Beam shot at 2m distance from the wall. Left is ARC-AAA-P and right is ARC-AAA-8mm.



I haven't done the runtime test yet, I don't have equipment to measure the light output (not even relative value, would someone teach me a simple way?).

But it draws about 0.36A from a fresh AAA alkaline compared to 0.21A of ARC-AAA-P. So a rough estimate is to expect 2-3 hours compared to 5 hours of ARC-AAA. (just estimate based on propotion only)

After running for 1 hour, it is slightly warm but not really noticeable.

I was hoping to overdrive this 8mm led to 150mA (spec 100mA), but ended up under-drive at 80mA. I hope someone suggest me to achieve it.

DJP


Edit: URL for pictures changed.

djpark,

That's a very nice mod! /ubbthreads/images/graemlins/thumbsup.gif

Larry

great mod! /ubbthreads/images/graemlins/thumbsup.gif

very nice mod indeed /ubbthreads/images/graemlins/smile.gif

Nice! Maybe you would want to try this with a Arc AA? Since the reflector is bigger and you can possibly catch more side light?

Now that is an Arc AAA/AA I would want. Decent run times and bomb-proof like the normal AAA/AA. I wonder if Peter is pondering the 8mm LED? Great work, BTW... say, I have this Arc AA laying around...

I hope you are not using the silicon sealant that is meant for sealing bathtubs. They use acitic acid as the solvent, which is corrosive to copper parts, and is moderately conductive (maybe that's why you didn't get the full 150mA output---just my guess). If you don't want to make a permanant seal, plain candle wax works fine.

djpark..super interesting experiment you did with that new 8mm LED. /ubbthreads/images/graemlins/thumbsup.gif

Additional new idea: using a Photon-II with the 8mm and powered by 2 x 2032 Lithium cells.-Maybe using a thick shim/gasket to give proper spacing to accept the extra thickness of both the 8mm AND the fatter 2032s in place of the usual 2016 cells.

IMHO-the Korean(?) 8mm LED has a very promising new future -just like the Luxeon has shown. /ubbthreads/images/graemlins/cool.gif
Bravo!

Thanks for the comments.


Nerd: 55 degree viewing angle doesn't give much to side and I don't think I get more with AA head.

I did this mod as a practice before I get to AA since I have quite a few AAA heads from dpr. So I can afford to spoil the head if things go wrong while I have only 1 AA.


BentHeadTX: I wish I can try more of this. But with limited tools, making bigger hole is mostly hand work using drill and pile and gave me a few blisters on fingers.

If you want to try, I can send you a green and red 8mm leds. Green is super bright and red takes low voltage, either one will give you brighter light than stock Arc AAA.

If Arc were to use these leds, I would recommend to use their 5mm white since its 20 degree angle gives rather tight hotspot with slightly more throw, the tint is also very nice. I made one AAA head and now it is my edc.


LED mods As Small As Possible: Thanks for the advice.

I actually used one of those glass sealant (clear type), but later removed when I found that it didn't reach deep enough to fill the gap between led and the head. I never knew it is conductive.

The current was measured before fixing it to the head, so the sealant is not the cause. I am hoping to learn more from mod gurus like you.

vcal: The 8mm led gives quite nice output as a single "cheap" light source. But (IMHO) 100mA current with 4 leds in it, the output doesn't seem to be 4 times of the brightest white 5mm led except the beam is pure cool white and smooth.

They (ISP, Korea) also make wide angle 11mm 1W leds (Vf=3.0-3.6V If=350mA) as well as 60 degree high power 1W leds. The high power 1W leds is very much like Luxeon, but on a round heatsink instead of a star shape. However, I believe the light output is not as bright as Luxeon.

DJP

Noticed that you used alligator clips for connection during the testing and measuring phase. That could be the source of some of your problems. I have found that sometimes they are not able to achieve a solid connection and I get shocking losses. Jiggle them, clamp down harder, or use as many soldered connections as possible.

The other part of your problems may come from how you hook up the meter to measure your current. Remember that even the very best meters will exhibit some resistance, and we are dealing with relatively low power. So if you put your meter in series to measure the current, you would have to expect some changes in the actual power delivered to the LED. Try putting a very tiny amount of resistance in series (0.01R or lower) and measuring the voltage drop. Or better yet, if you have the characteristice I-V curve of the LED, measure the voltage across the LED and make an estimate.

Great experience.

The distance beam shot seem to be more useful.

[ QUOTE ]
Steelwolf said:
Noticed that you used alligator clips for connection during the testing and measuring phase. That could be the source of some of your problems. I have found that sometimes they are not able to achieve a solid connection and I get shocking losses. Jiggle them, clamp down harder, or use as many soldered connections as possible.


[/ QUOTE ]

The croc clips were used to connect FB (feedback), battery and led while capacitor and inductor were soldered. But the length of the wires were long and I suspect it would have contributed to the problem.

I will connect the wires as short as possible and try again someday.

DJP

If all you want to measure is the relative light output as in how much it dims relative to the starting level or how bright it is relative to other lights that you measure with the same gear, then you've got all you need. Just hook another diode to your DMM and place it in the light, aim it at the light and read the meter. They are photo-diodes afterall.

I wonder how this one compares to an Arc AAA Luxeon + micro converter mod... djpark, I don't suppose you have one also, or you would have posted beamshot comparison pics already, right? /ubbthreads/images/graemlins/naughty.gif

Thanks! /ubbthreads/images/graemlins/thumbsup.gif

[ QUOTE ]
ESD said:
If all you want to measure is the relative light output as in how much it dims relative to the starting level or how bright it is relative to other lights that you measure with the same gear, then you've got all you need. Just hook another diode to your DMM and place it in the light, aim it at the light and read the meter. They are photo-diodes afterall.

[/ QUOTE ]

Thanks for the info. Something new! I presume you are reffering to another "led", and measure the voltage output, right?

I found a related circuit using the "photo-voltaic voltage" of an ordinary led at Bowden's Hobby Circuits. In his circuit, he used FET to amplify the voltage. Is the voltage from led sufficient to drive the DMM or PIC-ADC? I guess we just try it out.


[ QUOTE ]
dabiscake said:
I wonder how this one compares to an Arc AAA Luxeon + micro converter mod... djpark, I don't suppose you have one also, or you would have posted beamshot comparison pics already, right? /ubbthreads/images/graemlins/naughty.gif

Thanks! /ubbthreads/images/graemlins/thumbsup.gif

[/ QUOTE ]

I had only one Micro Converter and it is in the AAA with 8mm now. What an expensive converter for a cheap led. /ubbthreads/images/graemlins/frown.gif

I did try Luxeon with the same converter before I put it for 8mm and felt that the light output is not that impressive with significantly under-driven current flow.

Even though the 8mm has more useful light (tighter beam) than stock Arc-AAA, it has less spill and I still feel that it is not bright enough at times. This brings again the dilemma of choices between brightness vs runtime and tight beam vs large spill.

How I wish I can have all of them!!

ESD: I tried the "photo-voltaic voltage" you suggested and it is very interesting. Different leds gave different voltage output when exposed to the light.

White led gave about 1V output when the led is less than 1cm from the light source. The red led gave about 1.5-1.6V and blue led produced about 1.9V at maximum light intensity. The voltage dropped quickly as the light was moved farther from the led.

Its current through the DMM without the load is about 1-1.5uA. I am not sure if this is enough to drive a regular ADC chip or need an opamp.

I suspect that the top voltage is saturated and the result may not be linear, but would give quite good indication of relative light intensity and very useful for runtime test.

-- DJP

Try shorter test leads. I used to run in to problem like yours and some cpf members said it has something to do with induction. Now I try to elimate crococlips and go direct soldering wherever possible.

Looks like the 8mm LED is here to stand in between 5mm and Luxeon LEDs. No more sinful underdrive Luxeons I am going for 8mm next time for anything below 200ma.

Vince.

[ QUOTE ]
koala said:
No more sinful underdrive Luxeons I am going for 8mm next time for anything below 200ma.


[/ QUOTE ]

Yes, I understand the guilt of not doing a justice. I am feeling one now for the converter.

-- DJP

I don't care for the fact that the LED is that exposed.

Well, now you know why I said "relative". ;-) Without some reference you can use for calibration, all it will tell you is which is brighter and to a certain extent, by how much. Look around and pick an LED that has a wide range and sensitivity, or pick a store like Mouser or Digikey and get a proper photodiode or three. Establish a "standard" setup like 1 meter away from the light, on axis, using the same diode and hookup to the meter and start recording your results. With some practice, not much as you appear to have the skills, you will be able to condfidently say things like "LEDX at 200ma is 20% brighter than LEDY at 200ma". You can also measure the beam width or throw with an objective reference. Say you define the spot as where ever the beam intensity drops to 50% of the peak. You can now translate that into angles and graphs. Runtime graphs of intensity are also possible.

Having fun yet?