Issue with FET driver and 3v XHP50.2

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Yourrid
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Issue with FET driver and 3v XHP50.2

Hey gang, I’m having some trouble with 2 different lights, and want yall’s opinions. I recently put a 3v XHP50.2 into a Convoy S2+ with a RMM FET (I think it is a FET+1; purple driver with MTN-17DD on the bottom) and another XHP50.2 3v into a Jaxman Z1 with a 22mm FET+1. I’ve noticed that right off the bat the mode groups get really funky. I’ll have it on low, and it will jump to high. Or high will jump to low. The S2+ is almost always stuck on high for some reason, even after trying to go through the guppydrv mode selections.

The Jaxman is doing something pretty interesting as well. Check out the video…


What I’ve tried/ruled out:
  • Neither have turbo timers
  • I’ve ruled out tailcap issues by using a metal screw driver in lieu of the tailcap (both still have issues).
  • The driver on the S2+ is soldered to the pill; the Z1 is very firm in the pill (so no grounding issues)
  • LED wires aren’t grounding on anything

I’m going to throw the XML2 back in the Jaxman Z1 and see if it changes anything. It was working perfectly fine before I put the XHP50.2 in so I’m trying to figure out what’s going on. Is there an issue with a 3v 50.2 pulling too much current through the driver that it forgets its modes and changes brightness on its own? Please tell me how I am “flashlight-ing” incorrectly Smile

EasyB
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The video looks like it could be low voltage protection kicking in. What cell with what voltage are you using?

For the other light (S2+) your description sounds like something different. What FW is in that light? I know that drivers with attiny25 have had issues with voltage spikes from high current setups. The voltage spikes caused the mcu to reset. Not sure if that would cause the behavior you’re seeing. Is the light set up to always start in high mode?

Edit: I see you said guppydrv so it has attiny13 I think.

Actually that almost sounds like an intermittent short from LED minus to ground. Check if the reflector is maybe touching the LED solder points.

Yourrid
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EasyB wrote:
The video looks like it could be low voltage protection kicking in. What cell with what voltage are you using?

For the other light (S2+) your description sounds like something different. What FW is in that light? I know that drivers with attiny25 have had issues with voltage spikes from high current setups. The voltage spikes caused the mcu to reset. Not sure if that would cause the behavior you’re seeing. Is the light set up to always start in high mode?

Edit: I see you said guppydrv so it has attiny13 I think.

Actually that almost sounds like an intermittent short from LED minus to ground. Check if the reflector is maybe touching the LED solder points.

The Jaxman Z1 has an Efest 26650 in it, running a regular 3v FET. The S2+ has a Samsung 30Q in it. So I’m assuming both batteries should handle the draw (both are fresh off the charger and still exhibit the same issues).

I checked the reflector on the Z1. The Z1 has a retaining ring over the LED, but I never got around to installing it due to the mode issues. So there’s zero grounding. I’ll double check the S2+, but I think I used Kapton tape on the bottom of the reflector to be extra safe…

Scallywag
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If you have a spotty ground contact on the driver, it will register as momentary disconnects – just like a half-press of the tailswitch. Double-check your current path for issues like that.