A neat fix for the HS21 parasitic drain problem

[Serlite]

Back when the Sofirn HS21 first released, I was enamoured with just how much it had going for it - regulated output, a cool UI, loads of emitters…the only flaw seemed to be its parasitic drain from the IR sensors.

Some of the first fixes for this were quick and easy - just slapping some black tape over the IR sensors. After mulling over it for a while though, I stumbled across a perfect solution - those silicone caps you put on chair legs:

With the addition of this cap, the sensors are shrouded in darkness, minimizing parasitic drain. Additionally, the sensors and charging port are extra waterproof, and it’s now easier to adjust the tilt of the light from the side.

Searching for “rubber end cap” on AliExpress got me plenty of results, and the 23.7mm diameter cap was a perfectly snug fit. I ordered from this seller, but there are many others!

[OrionRipper]

That’s cool, can’t you just turn off the sensors though so there wouldn’t be any parasitic drain?

[CookieDave]

Good to know that fits. I just slapped a piece of electrical tape over the sensor on mine, but that cover might also double for some light water protection as well.

[Serlite]

@OrionRipper

That’s cool, can’t you just turn off the sensors though so there wouldn’t be any parasitic drain?

Strangely not - from other people’s testing, it seemed even when that functionality was turned off the IR sensors still had some parasitic drain, which got worse with brighter environments.

[OrionRipper]

Interesting, thank you for telling me. I received my HS21 a few days ago so I’ll certainly put something over it.

[jon_slider]

@Serlite

the IR sensors still had some parasitic drain, which got worse with brighter environments.

very well summarized,
here is the original post about it:

@koef3

The parasitic drain depends on the ambient brightness.

The current of 1.88 mA drops to 40 µA after some seconds, but only in a dark environment .

Anyway, if the light is stored in a brighter environment (1000 lx) the drain goes up to 0.33 mA, and in sunlight (over 100000 lx) it sometimes jumps over 1 mA. This is caused by the IR sensors. They induce a current which is generated by the ambient light.

[RichH]

@Serlite

Strangely not - from other people’s testing, it seemed even when that functionality was turned off the IR sensors still had some parasitic drain, which got worse with brighter environments.

Thanks for letting me know, mine is stored at the ready, hooked over the headrest of one of the seats in my van. Definitely going to need a cap as it’s in the sun a fair bit. Second mod for this light, first was sanding off the ridge on the head strap to adjust the light up and down easier.

Be interesting to test the battery, I haven’t used it in a few weeks.

[mcjtom]

Another way to do that that has been suggested is sticking a little black Blue-tack or silicone into the sensor pinholes.

As for waterproofness, I opened this end and there are gaskets all around, even for IR sender/receiver sitting under those pinholes.