MRsDNF likes attachments on his toys…
Has anyone tried these DD FET based drivers using 4S AA Eneloops and a single xml emitter?
Wondering if the voltage would sag enough for an emitter on copper to survive.
Probably same as a Nanjg - if the MCU can take it - is it a total of 6V fully charged? If so, on the borderline for the MCU - might need the zener mod. I would think a FET DD or 7135 driver would have the same issues? Dunno details, but I believe the LED will take what voltage it needs from the cell - for example using a 4.2v charged cell is too high for the LED, but it still works fine, but there must a high voltage limit for the LED... Not sure off hand - probably on the CREE spec sheets.
At 7amps a full eneloop AA sags to ~1.1V (HKJ's results), that is 4.4V for four in series. At 7amps a xml2 on copper needs 4V, so with no resistances the current will be more than 7 amps. But there will be resistance, especially with cells in series, so you might just get away with it and have a very nice DD- light :-)
But I don't know what voltage the mcu gets for a brief moment at startup, might be the full 5.4V, and still should survive that.
Thanks Tom E and djozz. I should have thought to look through HKJ's work for eneloop voltage charts.
Yeah, it might be better if I reserve 4AA to a multi-emitter application. It's just too hard for me to not try to take all the resistance I can out of a light. Even if it needs some. Some type of OCDitus, I guess.
Back to topic - I ordered qty 6 of these BLF17DD V1.0 boards today, so couple of weeks I'll post detailed pics.
The MCU was getting a fairly steady 6 volts before the capacitor revision and still survived, 5.6v no-load won't be a problem. The LED is another matter.
Springs and a switch add more resistance than you would think. No need to intentionally add resistance, just don't go overboard trying to eliminate it. You could also use one of the crappier FETs left over from other discarded drivers, 20-30 milliohms in the FET would give a reasonable amount of limiting.
The link for the newest BLF 17DD has been added to the Oshpark thread. It has the revised location for C1 and pads for an off time cap.
CC Could you weigh in on a similar subject here in my RGB driver thread (post 34 if using different page settings)? By using different FET’s could I get away without limit resistors at all? To me that would be an ideal solution cause of space, the 14-pin PIC controller is larger than the tiny84 so I need to do some magic or something.
Ignoring the lower vf and just trying to deliver it less current but without changing the settings
Not really on the same scale, you'll need a resistor of several ohms (haven't done the math, just as a guess) to get the Vf down, not milliohms.
I’ve modified a few Nanjg’s with FET’s, & reflashed without a problem, but today I built my first BLF17DD board from scratch. First scratch-built board, & first time using hot air reflow & solder paste. I’m happy with how it all went together - very neat with the solder paste & hot air - makes it pretty easy 
I got a few kits from RMM - it’s the Rev2 board, & I’ve changed the CAP location from B+ to GND & bridged the R3 pads.
Problem; Works fine on high / turbo, but on low it will work for around 5 seconds, then start to pulse at around 2Hz.
On Medium modes, it will also work for a few seconds, then will start pulsing & also changing modes randomly.
I’ve tried several different firmwares, & tried fast & phase-correct PWM, but it makes no difference.
In addition to this mode memory does not work in any of the firmwares I tried.
Anyone come across this type of behavior before? I’m thinking that the ATtiny may be faulty.
Thanks.
Can you show exactly where you put the capacitor?
See if it acts better when the diode is jumpered. If you're testing it out in the open, grab across the diode with tweezers to short it.
More than that I can't say, I don't know which exact components RMM sends with these drivers, I have only worked with the parts in the Digikey lists.
The CAP is as your picture in the ohs park thread post 1045
I’ll try the tweezers on the diode in the morning - I’ve packed it in for tonight.
All of the parts in the kit from Richard are the same values as I’m seeing in your pictures.
Please post pictures when you get back to it. At one time, there were so many different versions and revisions with no coherent naming scheme that it's possible the person who placed the Oshpark order is the only one who knows which one it is.
Make sure the capacitor is properly soldered. I had one that constantly gave the low voltage warning blinks & step-down no matter what, everything looked perfect, but after re-soldering the R1/R2 resistors it was cured.
Comfychair was just cross posting the info in that thread. This is the main thread for that testing project: FETs and gate resistors - scope images. [Post #1045 ~= Post #55 there]
Just to be clear, the post you referred to contains two configurations (marked V1 and V2 in red text in the upper right corner). Which one you are you using?
Regardless of what you have now I’d try the other config! V1~~V2 or V2~~>V1. They aren’t really versions, just different configurations.
I assume that you are using 1s, not 2s or more (zener setup). If you are using >1 battery in series you should let us know. What current level are you achieving on your highest level? Higher currents should create a larger field resulting in a larger spike as the FET turns off. This may require more capacitance between B+ and GND.
Wight, I’m using the v2 config., single cell. I know it’s all still work in progress…that ‘v2’ config seemed to be the latest solution from what I read.
That’s right. Depending on your drive current you may need to increase the capacitance, but that’s really just speculation.
If you don’t know your drive current you could just post what LED you are driving off of what cell.
Nice effort FmC. Good luck with the fix.
The board I have is identical to the one in the first two pictures in the OP of this thread. For testing, I'm using an XML, powered by a single Samsung ICR18650-28A laptop pull. It was at 4.2v at the start of testing. Using fairly thin long jumper cables, going through an Omten clicky. I was initially using short 22awg, but changing to the jumper cables/switch made no difference either way to the problem.
This morning, I re-soldered each component on the back of the board (CAP, Diode, & the two resistors), one at a time, & tested each time, with the problem persisting. I also tried the tweezers bridging over the diode.
I previously mentioned that mode memory didn't appear to work - to clarify that, it had 'next mode' memory.
I bridged star 4 to ground, then it would only operate in medium mode - nothing else, no pulses, flashes, or mode changes.
Not really getting anywhere, I decided to move the CAP back to C1, & replace the bridge on R3 with the 100 ohm resistor, exactly like in the first two pictures in the OP of this thread.
Problem is now gone...
I would have liked to get a more definitive result using the 'v2' cap arrangement, but this driver is going into a light for a workmate, & right now it's working, allbeit with the spikes that only me & you know about....
I'll put together another board, using the same layout I had the problems with, just to see if the same thing happens.
Does anyone know of an equivalent to http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=155125628&uq=635430913889454363 (AOD510 MOSFET) on mouser.com? Their prices are a bit better for the rest of the components for this build and I only want to pay shipping once.
Nevermind. Ordered from Digikey.