Code now public! BLF A6 FET+7135 Light. Short 18350 tubes and Unanodized Lights Available

The capacitor is labeled as ‘OTC’ (Off-Time-Capacitor):

I do not have a light open, but from the photo it looks like a 0603 package. A 0805 could also be made to fit.
The ‘standard’ OTC seems to be 1 uF.

So we need a 1 uF, 0603 size, 10% or better, 10 V or more, X7R capacitor.

I like the selection filter at Digikey:

http://www.digikey.com/product-search/en?FV=fff40002%2Cfff8000b%2Cc0002%2Cc0003%2Cc0004%2C3400fd%2C3405f9%2C380004%2C380009%2C380014%2C400005%2C440005&k=x7r&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&pbfree=0&rohs=0&quantity=10&ptm=0&fid=0&pageSize=25

But better wait for TK to weigh in - I think there might be some calibration to do in software for each board to get the timing perfect.
So do not try this if you are not able to re-flash the controller.
(On the other hand, how much worse can 10% tolerance be compared to the temperature shift of lower grade capacitors?)

EDIT: Tried one of mine and it cycles correctly when hot.
EDIT 2: Playing some more and giving time for the heat to spread, mine does it as well. Difficult to time, but a long click becomes less than 0.5s.

I thought it was my battery getting low, but I guess its heat, mine does the same.

TK confirmed with me it’s a temperature related issue. Shorter presses when it heats up fixes it

The offtime capacitor discharges faster when it’s hot, so it makes the button timings speed up when hot and slow down when cold.

We managed to greatly reduce this effect, but couldn’t eliminate it entirely. So, when it’s hot, a “medium” press is faster than usual. And if you put the light in a freezer, a medium press will be slower than usual. In my tests, the timing changes by a factor of about 2, which is way better than the factor-of-10 sensitivity it originally had.

So, if it’s really hot, try holding the button half as long. Or if it’s really cold, try holding it twice as long. Hopefully this can be fixed sometime soon; I hear that using an X7R capacitor might help (Thanks, DEL!). I’ve added this hardware change to the list of things which need to be fixed in new lights.

Finally received my A6 today but unfortunately it is (almost) dead. Only when screwing on the tailcap it makes very short contact but that could not be maintained for a longer period of time. Shorting the battery to the tube did produce a working light so it must the the tailcap or the connection of the tailcap to the tube.

Already emailed Neal assistant through the email address in the opening post. I hope this gets resolved soon.

In the mean time, you should be able to get it to work by bending a paperclip or wire and putting it into the tailcap. Something like this:

Yes,

Sounds like the tube is too short to make reliable contact to me.

They will send you a proper tube.

Thanks,
-Chuck

Please post back your contact (or no contact) experience. Trying to guess what the time frame is in resolving the problem.

Will try that tomorrow. Thanks!

After a bit of tag with the postal service, I finally got my 1A and 5A units in.

I was a bit nervous when putting in batteries but both units lit up instantly and I was able to step through the modes. Whew! :slight_smile:

One of the units had a loose ring rattling around inside the tube. Is that something to be concerned about?

Not sure what the bins are but the 1A is definitely a lot brighter than the old UltraFire 2100 XML T6 that I had been using. Though that also means the moon mode is also a lot brighter than the moon mode on the UF2100, which is too bad as I like low moon modes.

In any event, thanks to everyone for making this a reality!

Hello,

Would someone more experienced with the FET+7135 driver pls advise if the negative (black) wire is supposed to be “joined” to the top of the FET and one of the 7135 legs?

I tried to separate the solder joint from the 7135 and the amp draw seems to drop from 4+A to 3+.

Thanks in advance!

For critical timing applications, like analog filters, a Class 1 capacitor like C0G/NP0 is used.
They have an almost flat curve against temperature. They do not exist at this capacity and this small size though.

Class 2 like X7R are normally used in bypass and coupling/decoupling applications. They are more compact, but less stable. X7R is one of the better types, rated at +/- 15% from –55 C to 125 C. But we may have xxV or xxU on the boards (+22–82).

Random graph that looks accurate enough to illustrate the point:

I think we can live with the 15% drop in capacitance at 100 C that the X7R offers.
Alternatively we can use C0G capacitors. The maximum practical value will be ~ 0.047 uF so the timing with change by a factor of 20. Not sure this is feasible in the firmware?

Yes, they are joined on the PCB.
Both the 7135 and the FET ‘sinks’ the current from the LED in parallel.

The extra solder visible in my picture above is just a messy job from the factory.

Sounds like good engineering work to me. Thanks.

Can someone explain how do I open up the head?, unscrewed the brass(?) retaining ring but the driver won't come out.

It’s soldered to the star that the led is mounted to.

So, if I understand correctly, the X7R class capacitor reduces the temperature sensitivity but does not eliminate it entirely?

I’m not sure if a capacitor 1/20th the size would work or not. The driver measures voltage, not capacity, so it should depend on whether the capacitor can handle the same voltage with a similar discharge curve.

I have a firmware already made which blinks out the raw ADC value for the offtime capacitor. I use it for calibrating timing. I would imagine it should also work for a totally different capacitor, or at least would reveal whether it discharges in a manner which is useful for this purpose.

Is the reflector portion of the head screwed on?, based on your picture seems like the reflector part was removed...can't seem to unscrew it, did they use threadlock?

This is the part that I used in my driver builds. I never noticed any issues with mode changing when hot.

I finally opened mine up and found no force marks getting the MCPCB into the head. In fact, it was rather loose.

I also noticed that you “should” put the reflector over the emitter when you tighten the head.
This should reduce the risk of de-doming.

I put the spare tail-cap rubber over the switch. It has a much shorter nub and give it a more classic feel on the switch.

I am little disturbed that the switch is being squished with the brass ring. Mine was incredibly tight.

Solder didn’t look to bad on the MCPCB termination. Didn’t pull the driver yet.

Still a great light with an incredible UI!