Trying to remove strobe mode from led (circuit pictures included)

[Chris_83]

I purchases a flashlight with a board very similar to the one in the picture. Note there are three solder tags.

https://www.dropbox.com/s/a9zu1fmy3vdqvqt/Flashlight Circuit.jpg?dl=0

With my flashlight, soldering the blue negative wire to tag "B" causes the switch to cycle through a different lighting sequence which includes flashing "SOS" in Morse code.

Soldering the blue negative wire to tag "C" by passes the circuit and the on and off switch just turns on the flashlight to full power without any other options.

I hope this will be of help to someone.

Kind regards
Chris

 

[loneoceans]

I purchases a flashlight with a board very similar to the one in the picture. Note there are three solder tags.

https://www.dropbox.com/s/a9zu1fmy3vdqvqt/Flashlight Circuit.jpg?dl=0

With my flashlight, soldering the blue negative wire to tag "B" causes the switch to cycle through a different lighting sequence which includes flashing "SOS" in Morse code.

Soldering the blue negative wire to tag "C" by passes the circuit and the on and off switch just turns on the flashlight to full power without any other options.

I hope this will be of help to someone.

Kind regards
Chris

The circuit is extremely simple, but unfortunately there is no way to remove the 'strobe' mode, and as others have mentioned, it's easier to simply buy a replacement LED Driver board. For example, the one linked by Chris appears to be a 20mm or 17mm driver.

The 3-pin SOT23 device appears to be an integrated LED PWM driver chip with memory. The 1uF capacitor provides some charge for memory mode, and the other two pins simply act as a switch via an internal transistor to control LED brightness via PWM. Current limiting is provided by the 4 parallel resistors.

So far I've not been able to find any datasheet for that unknown IC but I'd be really interested if anyone could find more information about it. Otherwise my best guess is that it's a custom mass-produced flashlight IC produced by some chinese fab plant and used in all cheap flashlights

 

[Chris_R]

This is a BIT of a guess, but the only reason I can think they bother with the 1µ capacitor on the YN-20-3 is for timing the relatively slow flash.
They use timing to achieve "low" power, by pulsing the led on/off. (check a phone camera view of it on low - there will be moving bars) .

So you have

• annoying slow pulsing,
• useful fast pulsing (dim), and
• not pulsing,

(Slow pulsing is "Tactical", supposed to bogey-man scaring and cool, I assume )
If you remove the capacitor , presumably it would be just on, or just off.
If you replaced it with a smaller value you'd get faster pulses. If "slow" which currently is about what, 4Hz(?) were say 100Hz the light would probably just be "dim" .
So change the 1µF to something like 0.022µF = 22nF, or 10nF.
. See what happens!

If you aren't bothered about dim then just bypass the chip and connect power through the parallel resistors. I have 4 x 2R2, so 0.55 Ohms.
I'm playing with a 5W UV led but I get 140mA on Dim and 690mA on full. YMMV.
At 2W the LED gets too hot for my liking.