BLF17DD Troubleshooting

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fellfromtree
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BLF17DD Troubleshooting

I was wondering if anyone has seen this happen. I have one of these drivers piggy backed on a yezl stock driver used for an eswitch.

It’s been running good using some rigged software based on JonnyC Star code. It was running fine when I turned it off at the tail. When I turned it back on, it just sits at what looks like 50% pwm and no response to anything.

I took it apart and checked the Tiny13a with avrdude, everything checked out. I uploaded a fresh copy of the firmware, just in case something went crazy. Same result on the bench. I then flashed in the original star driver and it still runs at what looks like 50% when on, no modes.

I was wondering could this be the Mosfet needs replacing? Or is it the Tiny13a pwm that went (and still checks out good)? Or could this be something else that happens right when you need your light!

Thanks

EDIT Think I’m gonna replace one at a time to see.. I hope it isn’t a resistor have to order those. I was just wondering if it was a common thing to happen. I’ve banged around the stock buck driver on the yezl and drove it way over spec, they still keep chuggin Smile Oh well, I’ll fix it one way or another- or order another one from RMM. I just wish I knew what happened.

Edited by: fellfromtree on 10/24/2014 - 09:44
fellfromtree
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Bah the Fet went. I think gonna pass on the direct driver from now on. If the FET goes with a MNKE battery what good is direct drive.

I tested it with a good BLF17DD I have and the FET on the board in question is stuck at ~50%. It’s not FETTING anymore lol If that’s a word.. Oh well

comfychair
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I have 4 or 5 SRKs that all use that same FET and four Samsung 25Rs, haven't fried one yet (and many single cell lights). If 25Rs won't kill it a dinky MNKE 26650 sure isn't going to.

What's the voltage at the gate? If you ground the gate, does the LED turn off? If you jump B+ to the gate, does it go to normal full output?

RMM
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If it was being feed the correct gate voltage so it could turn on all the way I really doubt that the FET died due to overcurrent.  I have pushed 20A+ through these and they never even get too hot to touch.  What you could have been doing in that light isn't even close to enough to kill one of these.  Something else happened. 

Mountain Electronics : batteries, Noctigon, and much more! What's new? 

fellfromtree
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Had to take care of some business on the farm. Man it’s nice out. Let me get the measurement. It’s definitely the fet imo though, on the other driver I linked with ic clips to test it out. It was stuck with a brand new driver at 50% out. That’s the only thing connected that’s new. I guess could put full power to the gate and see if she goes full out. Sometimes it’s good to have more brains- I was going about it all complicated. But it’s definitely the fet imo Sad

Let me jumper and see what happens though. If it opens up I’d be very surprised.

EDIT Yep full power to the gate- same result. Oh well hey RMM I think saw those on your site for sale. I need to order one get this fixed. Maybe it was just a bad fet who knows.

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So you get this result on the bench as I read your post. 

This is just an idea.

Maybe try to test for continuity from various points on the driver to where there should be none. Sounds to me like you may have a leak current somewhere. Operative word: may 

Obvious ones are:

from spring to negative ring

From negative led pad to negative ring

From gate to negative ring

 

But sooner or later someone has to get a dud. Sorry if it turns out it is you.

 

~ Ledsmoke ~

Dutch humor:

[quote=djozz]

 I do not think that the BLF-community ben

fellfromtree
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Thanks for the tips led.. I put power direct to the gate though- it should have opened and didn’t. I’ve even tried with a brand new driver and ic clips to the fet. Same results. It’s just a dud Sad They’re cheap though only a buck each on mountain- already ordered. Picked up some efest batteries too, fry me another chicken.

But really I haven’t had a problem with that buck on the yezl. I braid the diode to the pill wall and it handles 6 amps with 2 batteries in series without breaking a sweat. One’s being used nightly by my redneck kin. I’ll fix this but I’m not too confident it will hold up. Be nice to compare the efest to the mkne. I have a feeling it’ll be the same though. Oh well Smile Live and learn.

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So it did not open at all?? Then I did not read that post right. Sorry for the confusion then.

~ Ledsmoke ~

Dutch humor:

[quote=djozz]

 I do not think that the BLF-community ben

fellfromtree
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Yeah thanks for the tips though. Not sure what happened really if it’s uncommon.

I think RMM gave me a dud! j/k I’ll update when it comes in. Why I outta! *shakes fist

wight
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fellfromtree wrote:
I have a thread on it lemme get.. http://budgetlightforum.com/node/35108

It’s the FET but I haven’t tried measuring LED- to GND when off.. I tried a few other things though including a new driver wired to the FET to eliminate the mcu

Fellfromtree mentioned this thread & problem over in the BLF17DD Info Thread – Reference (post #142) and I thought I’d chime in. Fellfromtree mentioned a suspicion that the gate drive resistor might be incorrectly spec’ed, but I don’t think that should be the problem. AFAIK the gate drive resistor is simply there to protect the MCU from a potentially heavy drain on it’s little 20mA-per-pin sourcing ability – NOT to protect the FET from anything at all. Besides just getting a bad FET, I think the most likely thing sounds like a sudden open circuit during operation.

Offhand I’m not sure if turning off the tail clicky should be able to cause a voltage spike, but disconnecting the LED definitely should be able to do that. (Due to the inductance in the wires to the LED.) Here it sounds like the LED was already securely wired in, so I suppose that we can assume the LED was not suddenly disconnected it. In that case I guess the tail clicky did it? Hmm.

BTW fellfromtree… you have confirmed that the LED is OK, right? EG at some point after this incident occurred you wired this LED up such that you saw that it is capable of lighting up at the normal maximum which you are accustomed to?

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

fellfromtree
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Yeah it’s good. I even took it all apart and used another led.

So a disconnect from the LED could cause the FET to go? That’s interesting stuff. I dunno what happened- I’ll replace it though and hopefully doesn’t happen again Smile It doesn’t light up to the normal through the FET, the gate is just stuck

Thanks Wight.. I’ll double check all my connects to the LED next time. I didn’t know a disconnect could cause something like that

wight
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I’m pretty sure it’s possible, but I wouldn’t really expect it to happen under normal circumstances either. More of a hypothetical problem. Long heavy gauge wires would probably make it more likely to happen, maybe especially if they were looped around a certain way (like an inductor).

If the FET is running cool then current flow isn’t bothering it. So while the FET is running cool the only potential problem is voltage spikes, and voltage spikes come from the inductive stuff going on in your wiring as the FET switches on and off.

I feel like you’ve probably hit the nail on the head when you say that you might have gotten a bum FET.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

comfychair
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In bench testing I've done all kinds of unapproved stuff like that - holding the emitter leads to the driver pads instead of soldering, just to get a quick reading on something, fingers slip, wires come loose, etc. If there's a wrong way to do it, I've done it, but no dead FETs.

wight
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comfychair wrote:

In bench testing I’ve done all kinds of unapproved stuff like that – holding the emitter leads to the driver pads instead of soldering, just to get a quick reading on something, fingers slip, wires come loose, etc. If there’s a wrong way to do it, I’ve done it, but no dead FETs.

Fair enough. My own behavior along those lines is what I was thinking of when I typed #11. I haven’t done a fraction of the fooling around with FET drivers that you have, but I’m sure that if suddenly disconnecting the LED normally killed FETs we’d know by now.

So, that said… what’s your theory on what did kill the FET? Fellfromtree has done the requested checks as far as I can see and the FET sounds like it is in fact dead…

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

comfychair
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When there's no rational explanation, blame it on ESD. Big Smile

Even though ESD happens with robust parts like this about as often as a rogue cosmic ray strike, you get taken seriously if you blame ESD.

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I have a 12*7135 (I stacked 4 chips) on a Convoy S2+ build I did, it ran fine for a while but now it won’t come on but in moonlight (lowest) mode for some reason

I wonder if possibly the diode feeding voltage and for reverse polarity is bad…I will have to check

NightSpy
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WarHawk-AVG wrote:
I have a 12*7135 (I stacked 4 chips) on a Convoy S2+ build I did, it ran fine for a while but now it won’t come on but in moonlight (lowest) mode for some reason

I wonder if possibly the diode feeding voltage and for reverse polarity is bad…I will have to check

I had that happen and it turned out to be a flux corrosion issue on one of the inputs to the XM-L emitter. Same deal, just a low moonlight output. Driver was fine, and the emitter was fine once removed from the MCPCB.

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NightSpy wrote:
WarHawk-AVG wrote:
I have a 12*7135 (I stacked 4 chips) on a Convoy S2+ build I did, it ran fine for a while but now it won’t come on but in moonlight (lowest) mode for some reason

I wonder if possibly the diode feeding voltage and for reverse polarity is bad…I will have to check

I had that happen and it turned out to be a flux corrosion issue on one of the inputs to the XM-L emitter. Same deal, just a low moonlight output. Driver was fine, and the emitter was fine once removed from the MCPCB.

It’s a 3x XP-G…ran great for about 5 min testing it out, shut it down…won’t come back on, I used a prototype ramping from turbo down to high (1 tick ever .25s) vs the large step down…I think it’s the firmware…but will re-flash just to make sure

But I will definitely check the inputs just to make sure…thanks!

hank
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Well, worth remembering that ESD adds up slowly over time, it’s not like being struck by lightning.
They used to call it “wounding” in the old days. A semiconductor has a narrow range within which it changes from being an insulator to a conductor — and ESD can change either side of that range by some small amount. Once enough components have wandered slightly off spec in various ways, the sum total performance of the circuit is, I believe the technical term used to be ‘cattywampus’

But maybe things like that don’t happen any more. I recall they never happened to young people, only to older people ….

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Just fixed it reflowed with a heat gun and tested- looks good

Good to know hank, I havent wore a ground strap in years, maybe that would be a good idea :bigsmile:

wight
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fellfromtree wrote:
Just fixed it reflowed with a heat gun and tested- looks good

http://i57.tinypic.com/1yllsh.jpg

Good to know hank, I havent wore a ground strap in years, maybe that would be a good idea :bigsmile:

You fixed it by reflowing the existing FET or by reflowing to swap on a new FET?

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

fellfromtree
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Doh you know I gotta start checking subs.. It was actually quite a crazy ride on this one. I took off the old FET with a heatgun, put on the new FET. But then I was tired and hooked up the positive and negative backwards on the bench xd The diode was bypassed because I was testing what mods I could make to the board- so I had a wire going B+ to the cap, bypassing the diode.

I wanted to see if I needed the cap or not, as I don’t monitor that or write to memory on the Tiny13a- trying to optimize it for future builds xd If you will.. Anyways The whole top end of the board started smoking. So I replaced the Tiny13a (checked out dead) and put in another FET as it wouldn’t fire up anymore. The stuff on the bottom all checked out. Then this is funny. I’m tired and solder fumes are giving me a headache. I clipped the led on, causing a short and shorting out the path. Turned it on to test- fried the diode (which I had just bypassed a minute ago).

Ok now I’m running out of parts. I put in a new diode and replaced the FET again just in case- it took a lot of juice through it with that short. Now my wife comes in and is like- what chu doing willis.. Well Fing up

So I learned a lot that night, I really didn’t lose out. I learned what blows in reverse polarity. I learned what blows on a short. So now I have a deep understanding on what not to do and hopefully wearing a mask will let me undo the rosin flux damage to my brain

wight
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Hmm.

  • Can you use pastebin or whatever you want to share the code you’re using which you think does not write to the flash?
  • The C1 cap is always required, it’s called a decoupling capacitor or bypass capacitor – it has nothing to do with memory or the flash. The offtime cap is only required for offtime firmwares, not ontime or momentary. (I do not know if the offtime cap is used for dual-switch firmwares.)
  • You fried the diode while it was bypassed?
  • ..or you unbypassed the diode and then fried it? Frying the diode with a dead-short from LED+ to LED- shouldn’t be possible I think.
  • Rather than a mask for those fumes, ventilation is the normal solution. Also called fume extraction. https://www.google.com/search?q=soldering+ventilation
  • Good thing these parts are cheap, right? Wink Silly

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

fellfromtree
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It’s all working now. Only fried the diode after I took out the bypass.. Which is funny cause I had it bypassed a minute before clipping the leads to the led without a isolator put on the bottom of the noctigon xd

Yeah reverse fried the mcu with the bypass.. Glad parts are cheap, and I learned a lot in the mess. Basically stupid stuff- I’m usually careful but get careless when I’m tired..

Thanks for the link on that cap wight :).. Was wondering if I could get rid of it. The code I used http://budgetlightforum.com/node/29150?page=19#comment-670322

EDIT I see it the OTC would be under Star 3 https://oshpark.com/shared_projects/lCBkc8G6

wight
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fellfromtree wrote:
It’s all working now. Only fried the diode after I took out the bypass.. Which is funny cause I had it bypassed a minute before clipping the leads to the led without a isolator put on the bottom of the noctigon xd

Yeah reverse fried the mcu with the bypass.. Glad parts are cheap, and I learned a lot in the mess. Basically stupid stuff- I’m usually careful but get careless when I’m tired..

Thanks for the link on that cap wight :).. Was wondering if I could get rid of it. The code I use is in JonnyC Star thread http://budgetlightforum.com/node/29150?page=19#comment-670322


  • I still really have no idea what you are trying to describe. I’d like to understand how the diode got fried and nothing you’ve mentioned so far actually says what you did in order to fry it. :~
  • I know (and hate) the feeling of making those stupid, careless mistakes while tired. You’d think we’d learn to avoid it! For my part I probably continue to venture into that territory because I’m stubborn.
  • Ah, that’s right you did post it there! A momentary flashlight is really the only way you can have more than a single mode and refrain from writing to the flash.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

fellfromtree
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Yeah I’m stubborn too when it comes to getting tired. Think my best ideas always come to me in my sleep. Like I used to wake up and write code that actually worked back in the day- same code I would be working on for two hours strait the night before with no results.

The diode, when I shorted out the led leads, forgot to put a piece of paper under the noctigon. Those MNKE batteries are supposed to do up to 32a- wish I didn’t throw away the bad FET from the reverse, it was melted on top lol

wight
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This is with an XM-L2 or something else? The XM-L2 thermal pad is isolated from both + and -. In other words AFAIK you could attach either GND, BAT+, PWM signal, or whatever to the bottom of the Noctigon and not cause a problem. I do not understand what problem was caused by not using your paper isolator – what do you have the thing resting on?

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

fellfromtree
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I clip them on with clips.. It’s probably not a good idea now that I think about it. Put a piece of paper under the mcpcb so the bottom of the clips don’t connect. *EDIT oh I see what your saying- no it just makes a strait short between the two

I looked at the diagram and I couldn’t see how the diode went either.. Think it would all go through the FET? All I know from experience is the diode goes if you short out LED+ and LED – on that driver.

wight
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Ahhhh, I understand now! I have my test MCPCB screwed to a very small heatsink, just solder wires onto it. (If you want to continue using clips my suggestion is to leave a pair of short wires soldered on {I’d us unequal lengths} and clip onto those.) Thanks for sticking with me until I understood.

Fair enough, it’s a mystery.

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
list of my drivers & variants (A17DD, FET+1 stuff, WIP stuff, etc)

fellfromtree
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I guess.. About half a volt makes it through the bad diode though. All I know is it’s stupid stuff.. You shouldn’t be bypassing the diode, then on top of that apply power backwards.. But somehow that happened. Then shorting the LED + and – when your tired shouldn’t happen either :bigsmile:

Good news is it’s done and the finished light worked great.. Sent it out yesterday morning Smile That’s the new U3 1A dedomed