[WIP] 17mm DD+single-7135 driver / single sided / Dual-PWM

I would test with a delay as the very first piece of code the MCU runs, before anything else. I’d do it to test if there is any change in the flash behavior. If no change is seen I would stop looking at code.

When I check signal traces with a DMM after hot air soldering everything on (beep on short circuit), I get short beeps when testing AMC traces to ground. If I get the beep or not depends on which probe (+ or -) I put on the trace. Could the flash you are seeing be a result of this behavior maybe? I don’t have any drivers or DMMs here now so I can say exactly which traces cause this, but this has most certainly been noticed by others.

Thanks for the idea. I put it on my list earlier today for the next time I have an affected light open, but I didn’t see it until after I had everything all put back together. Unfortunately, it doesn’t happen on any of my convenient test hosts… just on the lights which are kind of a pain to open and flash.

It’s possible I might not be able to trigger the bug with a pre-delay, since that gives the OTC extra time to change its charge, which might prevent the ability to change modes. But I’ll figure something out.

I originally posted this in the BLF Manker A6 thread, but it looks like this is the more appropriate thread.

I built many of Wight’s DD+7135 driver and never encountered the flicker issue. I saw the flicker with the Manker A6 driver. Comparing that with my home-assembled driver, I used a different MOSFET: PSMN6R5-25YLC instead of the PSMN3R0-30YL used in the Manker driver. I swapped the MOSFET in the Manker driver and the flicker disappeared.

Doing some research, I suspect the flicker issue is due to Cdv/dt induced turn-on.

When the FET is on in turbo mode, it causes the battery voltage to drop. When the FET is turned off in moon mode, the battery voltage recovers. This causes the change in drain-to-source voltage that triggers Cdv/dt turn-on. The white paper mentions that if the gate driver can only pull the gate down to 0.7V, then the Cdv/dt induced voltage is added to this 0.7V to make turn-on even more likely. I checked the ATtiny13A data sheet and the output low voltage is only guaranteed to 0.7V.

What makes matters worse is that the Vgs or gate turn-on voltage decreases when the junction temperature increases. So the longer the light is on turbo, the more likely that it will flicker when switched to moon.

Adding a pull-down resistor to the gate of the MOSFET, as Tom did, helps but does not completely eliminate the flicker. Beyond that, we can try the AC gate drive suggested in the paper by adding a capacitor in series between the MCU and the gate of the MOSFET; but this is more of a solution for the next driver design than a fix for the current driver.

The PSMN6R5-25YLC that I use has higher on resistance and so the turbo current will be lower. But will it still be acceptable? There are other parts in the same family that offer lower on resistance than the PSMN6R5-25YLC and lower stray capacitance than the PSMN3R0-30YL. Only by trial and error can we determine which ones are best. However, I don’t have the equipment (top batteries or thick probe wires) to do accurate current measurements.

Anyone willing to cooperate to find a better MOSFET for this driver?

What flicker do you mean?
The only thing I noticed with the BLF A6 flashlight is the following. If you are in turbo and use a short press to go to moon I see a very short flash and than a stable moon mode. Do you mean this short flash?

Yes he means that short flash.

Haven’t read the linked psdf files yet, but I Always appreciate Infos

whats the right equipment to flash this driver ?? /any recommendations from the pros here ??

In case you’re not using Windows, this includes some extra info and links to alternate tools and equipment:
http://bazaar.launchpad.net/~toykeeper/flashlight-firmware/trunk/view/head:/README

Has anyone received boards like mine? :~
They are v009 from the first post link.
I have never had problems with OSH park, how responsive are they to these issues?

wow - they don’t even look purple! OSH Park customer service is typically good!

is the BAT+ terminal pad underneath?

Yes, copper is underheath.
They really are purple, it is due to white balance of my phone with artificial (non-led 0:laughing: light (today it´s very cloudy here).
Thanks!

Yes, I've had the same problem, but think just once. Opened a ticket on it, and they explained they've been having this problem with Alex's board once in a while and not sure why. It does have to do where/how your batch is placed in the panel sent to the fab house. They were very accommodating and rushed a replacement batch sent free of charge. Still takes a week or two, but still great support.

I also used the masked ones - just had to scrape off the masking where I wanted to solder.

Hi Tom, your explanation is highly appreciated.
I also thought about removing mask, but i preffer contact them; i don’t want end up with ruined boards and without the possibility of asking for new ones.

Is v009 the latest and best version to order for a FET+7135 driver?

wight’s profile says he has been absent for a while so there were no updates in the OP.

thanks.

Pablo - The masking is easy to scrape off - I use an exacto type knife with a curved edge - works great, never had a problem - the curved edge is the important part, no point to deep scratch. Actually I do this all the time when I want to expose copper for grounds, or for other traces, etc.

tech - Well, I'm still using these v009's. Richard has an OSHPark design too, as well as other variations out there, maybe by PD68 and pyroson1.

This wight v009 was the board design the BLF A6 is based on.

Mmmm… i think i have a perfect knive for that somewhere, I might give it a try.

Thank you, Tom E.

guess I’ll order the v009’s

I think you can use really fine sandpaper, just lay it on a flat surface and you can sand off mask coating! At least I could try that method…

Yes, sanding is an option, but i have experienced lapping tiny things very difficult to do even, being borders worn much faster than center.

BTW, i already have a new boards bach on a new panel, nice good service from OSH park :bigsmile:

This is my first time building the a driver on my own. I have everything needed my question is do I flash the attiny before or after I bake it on the pcb? I assume I can flash and re-flash in circuit.
Thanks,
Neil