It looks and feel exactly as i expected from a Convoy ie : simple and robust with a clean finish
The only thing that ennoyed me somewhat once the "new toy" effect started to settle down was the feeling that the mid is not really enough (to my liking) for some serious work while the high (and the associated battery drain) is too high, wich was enough of an excuse to decide to open it and see if i could mod it ;-)
Pictures an schematic will follow asap but to make a long evening short and after verifying several time i have a question :
Is it common for that kind of flashlight to drive the led with a constant voltage (about 3.25V) through a low value resistor (0.2 ohms) with NO current feedback (or anything else that could make a decent current source) ?
I figured that while you need a boost converter and decide to add some kind of u-controller it wasn't that much work to have them drive the led in current mode ... but i might be wrong !*
*Long ago i have built a flashlight with cc mode driver (maybe i'll show you pictures of the poor ugly thing one day) but that was a single mode (and low power) one so it was no big deal
Thanks for the schematics and photos, those are always interesting to have :+1:
That driver configuration looks normal for a PWM-controlled LED.
Djozz has found the PWM frequency to be 744Hz, which is unfortunately low and makes the PWM flicker perceptible to a fair number of people. Djozz’s post with his impressions and test results is here:
@Kame Sennin
Thanks for the effort, that are very good pictures of the driver, and a schematic to boot
I’m not sure how this driver handles it, but I can say it’s not ‘common’. The PAM2803 based drivers are indeed current controlled with a sense resistor.
If the driver is in fact not current controlled but voltage controlled, it might be adapted for a certain LED. So R3 (R200) could be a current limiter, protecting the FET, or burning off excess voltage to adapt the output voltage of the boost circuit to the desired Vf of the LED. But I haven’t identified this T2 controller IC yet (I also presume the SOT23-5 with D3 on it).
A defining characteristic is the use of an external switch (8205S) in the boost circuit. I’m curious if the external switch would allow for a higher current than the PAM2803 drivers, although it’s not relevant for 1AA (1.2V) use. Here the cell is the limiting factor. But might be interesting for 2AA.
My hopes for an Attiny based driver are gone, of course, the MCU pinout is definitely not Attiny13A and it can’t be easily swapped. Strange to see the sub-par PWM and modes, it’s not typical for Convoy to use visible PWM and a disco mode in a single mode group. That’s what makes me think he just bought the driver and did not put own development into it. Or he sells more lights to muggles and they demand it… But although I don’t consider this driver suitable for use, it’s interesting to study it.
Some annotations to the schematic:
- C2 has the marking 476, which means 47000000pF (6 zeroes), so it’s 47µF.
- there’s a third ceramic capacitor on the board that’s not in your schematic
R5 is probably “01D” (zero one D) which means 100k in this code form
Again, I’m very grateful for the information you provided.
The T2 looks great, I consider it a great host, and I’m on my line of boost drivers again, which were a bit neglected in the past.
You are totally right about the 47uF, missing ceramic resistor (near the red wire) and "01D" resistor, i just updated the schematic.
It took me too much time to reverse engineer the schematic because i was looking for a current drive like the PAM2803 and couldn't have it to fit what was on the board ;-) and i was expecting an Attiny too :-(
From what i have seen, without a current mode drive (a higher voltage with a higher value serial resistor is a decent current drive at low power) the led output might change pretty much from one led to the other even in the same batch (U/I curve irregularity) and is more temperature sensitive but that is certainly not a real concern for that kind of use :-)
The parallel 8205S and rather small inductor certainly help its current capabilities but efficiency probably sucks. I’m a bit skeptical about that “800mA”.
I’d really love to see an output/runtime graph on High…
Nice find !! I have watched many small boost IC datasheets but couldn't find one that was totally fiting !
I am somewhat short of time at work right now but i hope to be able to take this driver to the bench soon and see what it can do
So now we only miss the MCU ... i have seen that "gnd at pin 8" on some cheap driver's picture already but don't know that kind of IC well enough to guess what it could be. Idea anyone ?
Could be one of the countless 8-bitters that Holtek makes. Cheap and generic. I’ve found quite a few that have GND on pin8 but pin3 would be reset I assume… no luck so far. Maybe a PIC12Fxxx or a clone, VDD and GND match too.
Does it really matter though? It’s going to be far easier to shoehorn in an Attiny.
Thumbs up for a link to the boost controller, I’m pretty sure I hadn’t seen that one.
I’m interested to see some performance values of the driver. I’ll buy me a pair of T2 at Fasttech, 12.47$ –5% BLF code = 11.85$ ist the best offer around. Banggood, Gearbest, all more expensive despite some code offers.
In the meantime, I need 2 measurements: The outer diameter of the driver (roughly to 1/10 of a mm) and the inner diameter of the retaining ring.
Much obliged.
I’m already tweaking my Oshpark boost drivers for the T2, I’m pretty sure I’ll build them myself as I’m not that fond of shoehorning MCUs… any more
Trying to measure the current drained from the battery whith an ampmeter did some very weird things at max brightness. I guess that the voltage loss in the measurement shunt was too high and made the driver to enter a very fast ON-OFF loop.
So i measured the voltage across a (very) low R shunt and got 3A max with a freshly charged eneloop.
Changed the 0.2 ohms limiting resistor in the driver of a second T2 (stupid me who didn't think of measuring this one before modification for reference !) for a 0.5 ohms, got about 2A max and then 1 ohm wich was 1A max
Lux measurments are from a calibrated Minolta T-10A using a 20cm polystyrene foam ball setup according to Djozz's "fast and cheap integrating sphere". As i don't have a calibrating light for now i have no good way to convert from lux to lumen but a Convoy S2+ with xm-l2 T6-4C at 1.4A (4*7135) in mid (40%) mode (should be about 200lm ?) reads 924 lux with the same setup.
Get the T2 from their Taobao store instead. 淘宝网 - 淘！我喜欢
Taobao Description:
(2) Low voltage protection: When the battery voltage is between 2.9 and 3.1V, the flashlight will alarm, showing a weak brightness with 2 flashes per second.
(3) Reverse battery protection: the battery will not light up, but there will be no abnormalities, no need to worry about burning the battery or circuit
It has low voltage protection and reverse battery protection while the one on Aliexpress store doesn’t have them. Pretty disappointing as the Aliexpress store is direct from Convoy. Anyone contacted Simon about this?
Thanks, but nope, don’t intend on getting it from TaoBao, even because I don’t have 14500 cells to toss in it so the LVP is moot and I don’t think they even ship to my country. If anything, I’ll wait for Simon to have his stock updated/upgraded.
Really nice look and feel. I’m a sucker for the S2+, and this is absolutely its little brother.
Greatest asset is that a driver of 17mm does fit. Makes DIY much easier, and the trade-off of a slightly larger diameter is really insignificant.
Lineup:
From left to right
SK68 clone, Ultrafire SK58, Convoy T2 (/w clip + sling), Thorfire TG06, Uniquefire G10, Utorch UT01, Convoy T2, Manker T01, Thrunite Archer 1A
Stock mode spacing is already really good, waaaaaay much better than most, especially the expensive AA lights. But doubleclick-to-strobe and PWM are a downside. Leaves room for improvement.
Got my Convoy T2 last week. Haven’t had much time to play with it. First impression, big and heavy for a AA only
If you like the smaller lights, I recently took delivery of a batch of small Sofirn lights - SF10, SF12, SF14v2.0 & SP10v2.0. The SP10 comes in black, red and blue.
