Building single cell 5mm led light

Well, I got a couple of GS leds left over and I was considering building up a single AAA cell (or AA) light with one emitter, I think... Only thing is, I haven't seen an efficient, compact, economical and durable driver that would be appropriate for a mag solitaire or similar host.

Any ideas for compact boost drivers to run a 5mm off of? :shrug:

Interesting. I think I've seen that before, but it certainly looks ideal.

What do you mean by "efficient"? Boost drivers in general are usually 70-80% at the very best. The Joule Thief was the first circuit that came to my mind as well, but it's even less efficient than that, IIRC (this site says 30% for the simplest version).

BTW, anyone know where to get really small ferrite beads for that? I want something the size of the last one mentioned here, that fits in an MES-type base. Also, what wire gauge for that size?

TigerhawkT3 said:

(this site says 30% for the simplest version).

Click to expand...

Those ASCII circuit diagrams are pretty neat, as if the name Lemon Vampire.

Any ideas for a pot to use in a solitaire? Seems ideal host beings readily available under $5 and the single AAA I'd like.

Do you know the PR4401? Two components only.
Simple, cheap and works nice (0,7-2,0V 10-20mA).
I´ve used one in a defective ARC AAA.





You can get the components here.
There are some other versions PR4402, PR4403.

Here is another option for you. Simple, easy to obtain components, and it will drain an alkaline AAA cell. I used 2N4401 transistors per a comment on another website. I have built these with both leaded and SMT parts, and the circuit has performed well. Sorry, I do not have any run-time information for you.

Modding a Soli for LED use is a royal pain - there isn't a lot of real estate available to cram all the electronic components.

LED_ASAP used to make a micro pill for the Soli. Another option is a little drop-in made by ArcMania; it's probably for sale at the Sandwhich Shoppe.

Check my site: http://www.quantsuff.com

I started with the Joule Thief type circuits and wnet on...

Builder said:

Check my site: http://www.quantsuff.com

Click to expand...

Your mini-"fluorescent" is cool. :thumbsup: Have you made the coil for that simply by wrapping the wire around the battery?

TorchBoy said:

Your mini-"fluorescent" is cool. :thumbsup: Have you made the coil for that simply by wrapping the wire around the battery?

Click to expand...

Thanks.

Yes, the coil uses the steel jacket of the battery as a inductance multiplier.

qs

Do you know this improvement of the Joule Thief?

I tried to build the "LED torch circuit B" and connected it to a Nichia GS, powered by one NiMH.
It works fine, nevertheless I get slightly different results from what the author reports.
When adding the 10n capacitor to change circuit A into circuit B, I do notice a significant decrease of the total current* in the circuit (let's call it Ic). But unlike the author ("The brightness of the LED did not alter") I see that the LED gets definitely dimmer. Then I tried with a smaller Vf LED (a red one), and this time the LED brightness did not change when adding the 10n.

My second attempts was with two NiMH as the power supply (so Vin was about 2.7 V since my batteries were freshly charged), and one Nichia.
In this case the capacitor did not affect the LED brightness (which is much brighter in this case than with 1 NiMH).
Then I put two Nichias in series: again the LEDs brightness decreased significantly with the capacitor.
So I came to the conclusion that the capacitor improvement does not affect the LED brightness only if Vin is not to low compared to the LEDs total Vf.

In fact my goal is to drive two Nichias with two NiMH (a bike light modification), so I tried it. First attempt with the original 2k7 resistor: the LEDs were much dimmer with the capacitor than without, not a good result.
So I tried to change the resistor value:
- R=2k --> the LEDs are still dimmed by adding the capacitor,
- R=1k5 --> no difference in LEDs brightness, with or without the capacitor. And Ic with the capacitor is about 1/3 Ic without the capacitor*.
- R=1k --> the LEDs are brighter with the capacitor (nice) but Ic is reduced only by 40%.

*important note: the currents were measured with a DMM, which I know is not good to measure such (pulsed) currents. But hopefully the current comparisons are somewhat realistic? This should be tested with an oscilloscope.

Re. the transformer: I was surprised to see that some of the designs mentioned above in this thread use very few turns around the ferrite core, and the same number of turns for the primary and secondary windings. The circuits I tried use a transformer with 60/40 turns. Is the number of turns of little importance?

For now I'll stick to circuit B with R=1k5, but I'm not very satisfied with the brightness of the LEDs once the batteries voltage is down to 1.2 V so any suggestion for a more efficient design to drive two Nichias with two NiMH would be welcome. I'd like the LEDs to be as bright as in the Fenix E01 (where they are driven @ 25 mA DC).