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. Djozzās 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
Iām not sure how this driver handles it, but I can say itās not ācommonā. 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 havenāt 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. Iām curious if the external switch would allow for a higher current than the PAM2803 drivers, although itās 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 canāt be easily swapped. Strange to see the sub-par PWM and modes, itās not typical for Convoy to use visible PWM and a disco mode in a single mode group. Thatās 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 itā¦ But although I donāt consider this driver suitable for use, itās interesting to study it.
Some annotations to the schematic:
- C2 has the marking 476, which means 47000000pF (6 zeroes), so itās 47ĀµF.
- thereās a third ceramic capacitor on the board thatās not in your schematic
R5 is probably ā01Dā (zero one D) which means 100k in this code form
Again, Iām very grateful for the information you provided.
The T2 looks great, I consider it a great host, and Iām 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. Iām a bit skeptical about that ā800mAā.
Iād really love to see an output/runtime graph on Highā¦
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. Iāve found quite a few that have GND on pin8 but pin3 would be reset I assumeā¦ no luck so far. Maybe a PIC12Fxxx or a clone, VDD and GND match too.
Does it really matter though? Itās going to be far easier to shoehorn in an Attiny.
Thumbs up for a link to the boost controller, Iām pretty sure I hadnāt seen that one.
Iām interested to see some performance values of the driver. Iāll buy me a pair of T2 at Fasttech, 12.47$ ā5% 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.
Iām already tweaking my Oshpark boost drivers for the T2, Iām pretty sure Iāll build them myself as Iām not that fond of shoehorning MCUsā¦ 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.
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 doesnāt have them. Pretty disappointing as the Aliexpress store is direct from Convoy. Anyone contacted Simon about this?
Thanks, but nope, donāt intend on getting it from TaoBao, even because I donāt have 14500 cells to toss in it so the LVP is moot and I donāt think they even ship to my country. If anything, Iāll wait for Simon to have his stock updated/upgraded.
Got 2x Convoy T2 from Fasttech. Iām very pleased.
The moment I held one in my hand I thought:
I need more
as host please!!!
do these come in colors???
Really nice look and feel. Iām 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. Havenāt 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.