Wish I knew the answer. I think CC recommended 16v rated caps and it does seem they would be adequate. I only use 50v caps because I regularly build 4S lights.
Perhaps 10uF is barely enough and then the combination of heat and some voltage (4v) is enough to bring capacitance lower than is needed.
That depends upon the dielectric type and the physical size of the cap. Smaller caps (for the same capacitance value) use dielectric materials that rend to be more susceptible to the effect… i.e. an 0805 X7R cap usually performs worse than a 1206 cap.
Also, we know there's a spike in this design, think from comfy's tests on a scope and think Richard confirmed, and the 13A can tolerate it, but we've been suspecting the 25/45/85 is more sensitive to it. On the 85's w/Narsil, the 0.1 uF cap across gnd and Vcc would fix it, but I thought that didn't seem to work on the 25 w/OTC firmware - I had it on and took it off. Ohh - I can still program the MCU's btw with the SOIC-8 clip with that cap jumper on the MCU.
Only thing that’s not working for me is the moon mode, it just doesn’t light up. Will try reflashing tomorrow to see if it’s just too low of a PWM-value.
Tom, did you manage to build a fully functional triple with a 25/85 driver yet? From your experience with that one issue not showing using a weak cell, I’d think the more amps we push through the FET the more likely we’ll see weird behavior… Also, did you always use SIR800DP as FET? Again, thanks for all the insights.
Hhmm, everything I got and used has been posted here, maybe not all summed up in one spot though.
The fuses are documented in the beginning of the source code, and also in the t85fuses.bat file, also shared on the google doc link (fuse values tell you the start-up time being used).
I'm @work now, so don't have access to all my resources though, and don't have the time here either.
I use the SIR800DP FET exclusively now.
For a triple? Yes - in a SupFire M6 that I upgraded. Also had enough problems with a 219C and a high amp single LED, and solved the problems.
For your moon mode problem, are you using a 380 mAh 7135? If so, you need a higher value PWM. You need maybe a min value of 4-5 for 380's, for 350's, a PWM value of 3 always worked for me, using PHASE mode of course, not FAST.
I ensure now I use only 350 mAh 7135's in all FET+1 drivers.
Thank you very much Tom. I’ve been reading through all different types of threads concerning driving a FET properly, but having major problems understanding everything and not confusing stuff. Even the “old” threads with great inputs from comfychair, PilotPTK, wight, JackCY and many more. What a pity most of these guys left and comfy’s pics are all gone… I’m glad that you’re still here!
ATM, I only have tiny25’s here, so my plan was to illuminate the bistro with a triple XP-L HI.
But with those issues reported especially with big amps, I thought I wouldn’t be able to get it running properly. Heck, I’ll just give it a try.
EDIT: yes, i was using 380mA AMC’s. Thanks for the advice
Hhmm, Mitko led me to believe the FET+1 wight drivers were maybe not performing so well, so my last driver mod/build was using a 25 on a single FET driver, and found the "fix" was to stack a 2nd 10 uF cap on the regular C1 cap (doubled up).
Didn't use Bistro, but believe I tried it and had the same problem before the fix, so I think the double up cap would work fine for Bistro. I'm thinking now, Mitko might have run across an issue with using firmware not supporting FET+1's well, where you don't get the max amps you can from the FET, so think it was a firmware issue, not hardware issue of the driver.
So it's weird, but, I got two fixes I've been using - a 0.01 uF cap across the grnd and VCC pins of the MCU (on FET+1's using Narsil), or stacked C1 caps (straight FET driver running my own firmware for a power switch light) or the equivalent with a 22 uF cap instead of the 10 uF used for C1.
Also the 12K resistor across the FET gate worked great to 100% eliminate the flicker going from hi to moon on a power switch setup using a Tiny25 with FET only driver.
Thanks again for taking your time and sharing very useful information Tom.
I played with my driver today, swapped the 380mA AMC for a 350mA one, still no moon. Had to adjust the values. I wonder why this driver doesn’t show any of the issues that’s been talked about. Maybe I’ll encounter some when I hook it up to a triple. It’s still driving a single XM-L2 now. I am also going to test a longer start up time fuse setting to see if that’ll make any difference.
I builded my first A85 driver today, tom`s design( Thanks for your effords mate) and initial tests shows its has great potential especialy in Y3 style/double flashlights, will update tomorroy with some questions cause my kids want a bed story
Started with
380mA AMC and PWM-value 3, no light.
350mA AMC, PWM-value 3, no light.
350mA AMC, PWM-value 4, one of the lowest lows I’ve seen. Very cool to look at, but for me maybe a bit too dimm in terms of useability.
350mA AMC, PWM-value 5, that’s what I went with for now.
I didn’t know that a X+1*AMC350mA-driver can give that low of a low mode!
I used TK’s level_calc.py to calculate ramp levels. More re-flashing to come, want to play around with it some more, calibrate voltage and adjust OTC-values to my liking (faster).
I agree with bugsy36, your Narsil looks very impressive, indeed.
Hi guys, could someone please help me with troubleshooting?
I’m trying to get bistro running on PD’s Double Down driver, but it won’t flash.
ATtiny25 is mounted to the driver already, driver is installed in a light with long wires.
I get this
verification error, first mismatch at byte 0x0000
0xff! = 0x87
I don’t think the problem is in the connection, I can flash tiny25 airwired, but not mounted. Have my connections to the programming clip like in Hoop’s tutorial.
Because of the long wires, I was able to desolder C1 and tried to flash again, same story.
Do I have other options before pulling off the tiny25 to flash it unmounted?
EDIT: Never mind. I don’t know how but I got it running. I have a new favorite light now:
EE X6 3x XP-L HI U6 5A, bistro on PD68DD with FET+2, it’s amazing!