Emisar KR4 stuck in strange mode

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Turby3Pots
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Emisar KR4 stuck in strange mode

Just received an 8 LED mule Emisar KR4 in the mail.

Turned it on and off a few times and now it is nonfunctional.

All I am able to do is hold the button down and it will ramp up, blinking heavily, until it goes solid and shuts off. No amount of clicking or battery pulling can get any other response.

Anyone have any suggestions? I cannot find any answer to factory reset option in the user’s manual.

Hank Wang
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The tailcap is not fully screwed in, you will need to screw the tailcap tightly.
When the tailcap is not fully screwed in, and you press the switch, it will be in the factory reset mode, just as you see now.

https://intl-outdoor.com, Noctigon, Emisar, flashlight components.

Turby3Pots
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That completely fixed it, thanks hank!

Yokiamy
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I experienced the same problem, i found out that tightening the tailcap solved the problem (as Hank described)
Probably a bad contact causes just too much voltage drop for the MCU to stutter.

ToyKeeper
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If the tail is loose, power isn’t connected.

However, a small amount of power can trickle through the switch, so pressing the switch powers up the light even when the tail is loose.

When the switch is held at boot time, the light enters factory reset mode. This mode ramps up while blinking, for about 3 seconds, as a warning… then performs a reset and ramps back down. The user can about the reset by letting go early.

So… because the tail was loose, the light was basically stuck in factory reset mode.

Yokiamy
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Thanks for the explanation TK!

Turby3Pots
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Yep it just makes too much sense.. It felt like it was trying to tell me something, the blinking getting brighter and brighter like it was warning me, and then the solid as a success message.

But I couldn’t (maybe still don’t) see how it was programmed to consider for a “loose but still slightly connected” tailcap? How was I supposed to enter this mode originally?

SammysHP
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There is no other way to do factory reset via the “hold button while tighten tailcap” with this flashlight (and I suggest to explicitly ignore the button event after boot, ToyKeeper). The other way is 13H from off.

ToyKeeper
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Turby3Pots wrote:
I couldn’t (maybe still don’t) see how it was programmed to consider for a “loose but still slightly connected” tailcap?

It’s not really a programming thing. It’s just a strange quirk of the way the circuit is designed. It can receive power without the battery tube installed at all, if you’re careful. Basically, put a battery between the head and the tail, with the inner tube in place but not the outer tube… then press the button. The light can turn on, but only at relatively low brightness levels.

When doing this though, power flows through the switch. So letting go of the switch forcefully turns the light off by physically disconnecting power.

It might be nicer if the light ignored button events at boot time, but then it would need a way to sense whether the light was actually just turned on, or if it was merely rebooted. That way, the 13H method would work, but the loosen-tailcap-then-hold-button method would not. Maybe the SRAM decay trick could be used for this. Then it would actually be able to tell the difference between a loose tailcap and an intentional reboot.

At the moment though, it has no idea whether the user did a 13H factory reset or a loose-tailcap reset.

Hank Wang
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Actually it’s much more easy to loose and tighten the head to do the factory reset instead of the tailcap.

https://intl-outdoor.com, Noctigon, Emisar, flashlight components.