I picked up this little red light to use on my bicycle. It doesn’t behave like my 529a T3 with regards to mode switching, and I’m wondering if that’s a quirk of the DR one or a defect. After all, the AliExpress listing for the T5 DR doesn’t document group configuration like the other T3/T5 listings do.
Specifically, I set the light to group 3 (should be something like 100%, 50%, 35%, etc.) but the brightness does not change when I tap the button. It doesn’t shine while I hold the button down, so I know the button works. I confirmed that everything is screwed together tightly, and tested the T5 head on another T3 body I have. Same result. This was all with a NiMH battery. With a 14500 cell it seems like I am switching between 100%, 50%, 50%, 50%.
This is some change Simon made to the driver for this setup right? Not a defect?
my limited understanding is that Red LEDs respond to a different Forward Voltage than White LEDs. But I have not looked up the exact Voltage specs for the LEDs in your lights.
I have several lights that came with White LEDs, and when I changed the LED to Red, the mode spacing was no longer the same.
For example my copper Maratac (middle in photo) now looks like it has 3 identical modes. They are actually slightly different when tested on my light meter, but the difference is not big enough to be visually different:
Simon does have the ability to build a driver specifically for Red, but I dont know what specific change he makes, and apparently in the case of your lights he did not use a Red specific driver.
This seems unusual. Convoy does have a special driver for AA/14500 red light. It is a single-group with 3 modes (low-med-high).
But it sounds like the white-light 12-groups driver was used when they assembled your light.
As you said
The red T3 is meant to use the special red-light driver as well.
The different forward voltage specs sound like a reasonable explanation. Interesting that I don’t appear to have gotten the red light driver. Oh well - this will still be a fun light to play around with
AFAIK even white LEDs with slight different Vf curve would screw with mode spacing. It has something to do with the sense resister works differently due to Vf difference despite it being a constant current design. I’ve seen it in my own modded lights. In my buck driven Fenix, if I switch the LED from 519A to LH351D (far higher Vf), the mode spacing goes from say 1-10-30-100 to 5-20-60-100.
ToyKeeper could chime in to explain this further. For a red LED, the Vf is far lower than typical white LEDs. White LED has typical Vf ranging from 2.7v to 3.7v. Red LED has Vf ranging from 2v to 2.5v. It’s enough to render the mode spacing useless.
I also remember Simon sells red specific driver. Maybe he used the wrong driver in your light?
I messaged Convoy - they confirmed mine has the wrong driver and offered to send me the correct one to install myself. I guess they saw my purchase history full of DIY parts and figured I could probably handle it. Acceptable resolution IMO.
I have to admit, my soldering skills are still elementary. But Convoy lights are where I’ve had the most success in my modding attempts. Lots of space inside (relatively), contacts are far enough apart that it’s easy to avoid shorts, no teeny tiny aux wires, etc. It also helps that spare parts are easy to get.
