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.
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?
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?
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.
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.
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
Neil - You can do it before or after, I've done them both ways.
Before: the SOIC-8 clip does seem to work fine with the "in air" MCU. Just be sure you get it positioned correctly before releasing pressure on the clip - clamping down on the MCU pins. I'm always concerned I'm gonna bend pins, but it never happened, but again, I'm extra careful before I let the clip clamp down on the pins in-air.
After: as long as you positioned the parts correctly, on this board you should be able to get a good clip on the MCU. Be sure your clip is wired correctly with a good ground. (lot of earlier posts and ref. pics and posts had it wrong!!). Also, I found it helps cleaning up the MCU pins with isopropyl alcohol to get off any residual flux from the reflow. I like using a small stiff brush.
Note: I updated the flashlight wiki page on the AVR Drivers for the ground pin connection here: http://flashlightwiki.com/AVR_Drivers. The ground is on dongle side pin #10 (or #8), not pin #4.
I was told to use a horse hair brush to clean pcbs; so I went to a nearby horse stable (fairly common here) and got some hair for free. bundled them into a brush and it works great.
