I have been building flashlights for some friends of mine, and I’ve been getting a lot of requests for single mode. So far, I have just been buying them flashed with Star from RMM, but I wonder if there is a way to do a hardware fix. I had heard somewhere that you can short the + wire to one of the 7135 pins to get a regulated single mode. Is that true? If not, is there any other way to get a regulated single mode (not direct drive)?
High mode only? Yep, just short the 7135 pwm to +.
It's easy to do. Just remove the MCU then short VDD to the PWM/GATE pin of the 7135s. That is what the MCU is doing, except at varying pulse modulation levels. You lose any sort of low voltage cutoff, etc. though. You can see what you need to bridge by looking at this driver.
Which 7135 pin is the pwm one?
I’m just “talking out of school” here, and I’ve been wrong often enough you should double-check, but…
The 7135 doesn’t do the PWM, it just limits current. The MCU turns the 7135s on & off by the “PB1” pin, AKA Pin6. The pin on the 7135s that turns them ON is #3, the one on the Right, looking at them from the top. AFAIK, you can make them “Always ON” (i.e. “one mode”) by connecting that pin to the ( + ) rail.
Here’s a picture I was recently given:
I beLIEve (but cannot prove until I test it later in the week) that bridging the RED line to the BLUE line will give you what you and I want, a fully regulated single mode. It may kill your MCU, though, if not the entire driver, if not the operator… At a minimum you’ll lose low-voltage detection, so you will need to develop the habit of “recharge early, recharge often” to keep from killing 18650s.
Personally I wouldn’t want to lose low-voltage detection.
Bridge vcc to blue (instead of Vin / LED) and at least you’ll retain reverse polarity protection.
Thanks, Dimbo, the picture really helps! It’s also consistent with what RMM said (thank you too, RMM!).
I’m thinking the ideal way would be to reflash the mcu but baring that do what Helios and RMM said. Removing the mcu (or just clipping the vcc pin) will save you a few mA and shorting to vcc will keep the reverse polarity diode in the circuit. Shorting directly to B+ would add a few minutes in regulation. Your choice.