A member here approached me about making a low output, long runtime boost driver to fit the Convoy T2 (aka Manta Ray S1, also available as a host at Kaidomain). Target output was ~1 lumen. No mode switching. Currently 17mm but could be made to be 15mm or about any size.
I went through a couple iterations and ended up creating one that ran an XM-L2 at 2.5mA for ~0.7 lumen for 98 hours on a 900 mAh AAA Eneloop Pro. So on a AA battery, it should run for 12+ days. It runs down to ~0.7 V.
Current is set with a single resistor. Current output could easily be set higher or lower as desired.
That sounds really interesting. Depending on cost I would be interested in a couple. Maybe at your tested output and maybe something a little higher like 3-5lm. Is this a constant current driver or PWM? What is the input voltage range (ie: is it adaptable to 2AA)?
Constant current (though technically due to the inductor there’s a high frequency ripple… but that’s how boost drivers work).
3-5 lm isn’t a problem, though I need to see which of these drivers would be most efficient at that output. While the ZXLD381 didn’t do great for super-low current, 3-5 lm might be in it’s sweet spot
Re: 2AA… in short: shouldn’t be a problem. Long version: the TLV61220 is rated for 0.7 - 5.5V. It has a 0.5V feedback, so if a LED is dropping 2.5V at the preset current target, the boost driver will put out 3.0V (2.5V for the LED and 0.5V for the feedback). If the input voltage exceeds what is needed to hit the current target, I think the TLV61220 will probably go into pass-through. In which case, it might be a touch brighter than anticipated until the battery voltage falls a little bit. With NiMH (2AA ~= 2.4V) this should be a non-issue. With 2 fresh alkalines and a very low current, it might start out just a touch higher than it needs. I can test this out more.
Cost: partially depends on how many I make. For the TLV61220 circuit (the better option for really low output) PCB + components are around $2.50 in materials (plus Mouser $3.49 shipping). I would charge actual shipping amount and next to nothing for assembly. For the ZXLD381 (good for currents in the 6.5 - 20mA range), I already have PCBs and components on hand… cost would be like $2 plus actual shipping.
Nope! I measured 0.7lm at 2.5mA to the LED. I could drop that down as low as 0.1mA (anything below that and efficiency would likely drop considerably). So even if you wanted 0.1lm, that should be well within reason.
This is great news
I may be interested 2x17mm and at least 2x15mm, in case you can ship them internationally.
Would it be “good to use” with other leds too? (ex: Luxeon V2)
Great
Hum, I know it is a bit more expensive, I had to pay that when I ordered from MTN, but I don’t mind!
So, in case you accept my “order” (whenever you can make and ship them), I would definitely get 2x17mm and 2x15mm! :+1:
Hmmm tempting, although I have no suitable hosts atm and shipping is a bit pricey. Maybe if there were a lot of UK/EU demand we could do a group buy and have one person this side of the pond re-ship them?
Alright, looks like there’s a bit of interest. So I’ll establish some pricing and get a list going. After gathering a list for a few days, I’ll order the parts to assemble however many I get on the list. I’ll try to keep this post updated.
Pricing: $4 per driver including spring and wires (TLV61220 version) or $3 (ZXLD381 version)
Shipping: $3.50 for US, $14 for International
When making your request, please specify:
Driver size (15mm or 17mm… or if there’s another you’d like)
Desired LED current and/or lumen output (I’ll try to guess about how much mA it will take to get the desire lumen output)
Special considerations (such as if you want to use 2AA… I will make sure to test this)
Funnily enough the sense resistors are the hardest things for me to source in small quantities for a reasonable price.
So I’ll probably do the same as MascaratumB and buy four (one of each combo) direct from you.
Output wise I’m thinking of 0.1-0.5 lumens and 3-5 lumens with sliced SST-20 2700K JA3 and 4000K FB4. Would it be possible to buy extra sense resistors from you at the same time? Will be useful to tweak output in the future based on LED.
Based on my limited knowledge it looks like this driver doesn’t really have any brains so I assume additional modes are out of the question? How about lit tailcaps?
I stumbled across this board recently when I was poking around OSH Park looking for joule thief drivers for 5mm LEDs and I’ve been meaning to ask you about it.
You’ve come up with some really great stuff lately. After you sent me some booster tail boards I ordered your LVP version. I finally got around to assembling it a few days ago (my first PCB assembly) and now I’ve got some of your indicator boards on the way.
Would this driver work with a red LED, or would the lower voltage be a problem?
Do you think it would be feasible to make a 10mm version for AAA lights? A couple of times I’ve purchased really cheap single mode AAA lights just to put the driver in a (slightly) nicer host that came with a high/low/strobe driver.
Typically what we call sensor resistors are low-Ohm, high-wattage buggers that are expensive and less common. In this driver, though, a run-of-the-mill 0805 1/8 or 1/16 watt resistor like you can get in bulk kits from places like Banggood, AliExpress, eBay, or any electronics supplier for like $0.01 each will work just fine.
I can definitely build them and send them your way. But if you can locate the parts locally, it’ll probably be considerably cheaper to do so.
Nope, this was designed to be extremely simple with no modes… just extended runtime. Running an MCU would require extra power and would decrease runtime. Lit tailcaps are also a no-go (unless perhaps my “booster tails”) as they would still be seeing the ~1.2 volts of the battery, no enough to run a typical tailcap.
Lower voltage shouldn’t be a problem. It should operate LEDs with a vF anywhere between 1.3 and 5.0 V.
I think so. I can play with the layout and see if 10mm will fit. Some AAA drivers have lobes on them. Are you thinking completely circular, or odd-shaped like that of the Astrolux A01 or Lumintop Worm or Tool AAA? Do you have a specific host in mind?
