There is no intrinsic difficulty in holding up the MCU during very short term power glitches, it’s just a matter of circuit design and bulk decoupling.
It’s something not necessarily done with clicky tail switches (where the driver is looking for power interruptions to change modes), but for an e-switch it shouldn’t be too difficult.
I’ll be taking a look myself, not knowing the detailed design or layout it might be as simple as adding a big bulk decoupler across the MCU, or not.
In my SRK clones its a big problem to fix (I have considered it) because the LED power is also on the same rail/PCB trace as the MCU, so the tens of amps possibly taken by the LEDs exhaust any simple add-on decoupler/holdup cap. instantly. I’d have to cut traces and add a couple of things to improve it. But if the MCU is isolated from the main power by e.g. reverse protection diode, maybe it isn’t too difficult to fix, depending on how the driver PCB is laid out. Shared trace with the LED + supply would be a bummer. I’ll take a detailed look once I have mine, because it really is an issue for me.
If so, maybe that could be filtered out in firmware, or the e-swtich powered from the same isolated well-decoupled rail as the MCU.
I’m anticipating that when the batteries lose contact with a bump, they will then bounce around a bit, predictable if you know mass of batteries and spring constant. Just as most mechanical switches and relay contacts “bounce”, once you look closely at them.
Edit: if one of the four cells was replaced with a very lightweight part, with a big capacitor inside (maybe supercap), that might be much more resistant to losing contact, even when the main cells do. If it had a small spring on the + end too, even better.
Might not be so simple if, as suggested MCU is indeed holding up, but false switch presses are being triggered by transients. Glad this little issue, which is important to me, is attracting attention, but will wait until I have my torch before jumping to conclusions.
Edit: PS Lexel, how do your drivers behave in this scenario ? Like the look of your dual 7135 bank ones.
@Tom,
what solder do you use for the springs? The stuff for electronics, multicore with 0.5mm OD with 4 percent silver?
Sn60PbAg = 60 Sn, 36 Pb, 4 Ag 180
I use Kester SN63PB37 #66/44 1.0MM ("44" rosin core), 1 LB spool that been lasting for couple years now, lot more to go. I work with a very senior super tech, who I think is the one recommending this. Right now I'm use no clean solder flux in a pen, but prefer using the better stuff, Kester #186 RMA, but hard to find and seems quite expensive now.
Wow, can’t believe the mod thread is up to 20 pages already. By the time I get my Q8, it will be double this. Has anyone swapped out the emitters yet…sorry…I’m not about to read through 20 pages to find out
Re: springs I’m considering using be-cu springs left from my Chimera build as inner springs with outer coated steel springs and punched copper buttons to lock the ends together. The be-cu spring would provide a low resistance path while the outer coated spring would improve compression resistance. I considered using the be-cu springs alone then did a tail impact test of the Chimera and found that after a moderate impact it went off then turbo (lexel 2s tactical dual switch srk driver). The be-cu and steel pair would essentially be using a be-cu spring as the bypass for the steel spring.
It would take a heck of a bump to disconnect all 4 batteries. With spring bypasses the wire makes the springs a tad bit stiffer so I don’t know if I can even get my Q8 to disconnect if I tried. Sanding down the battery tube also shaved off a fraction of a mm to make things more snug as well. Thinking of taking the tube down just a bit more to line up the flat spots, but I will wait for my screws to come in so I know the driver is sitting flat.
The ti-cu springs in my Chimera are 1mm, no bypass. An impact from about 1 ft to impact with the palm of my hand caused stated change. I suspect the method I suggested might prove to be better than a wire or wick bypass.
An additional 100 uF ceramic cap over C2 appears to be sufficient in my light. No power hickup on hardest bumps, even scratched the tailcap during tests.
bumps on the tail end will disconnect cells easier then on the side.
still, or a bike lght I would go with something with spring on both ends of the cell
A modding idea for getting springs on both ends, quite a solder job: on the tail side of the battery tube swap in shorter springs, on the driver side remove the brass ring, solder 3 or 4 short springs, i.e. the BeCu intl-outdoor springs, on the +pad and solder the brass ring on top op them.
Being realistic I can’t get my Q8 to turn off no matter how violently I shake it, only by dropping it onto my knee from 10in/25cm with the tailcap down can I get a consistent disconnect. I mount it to my bike in a way where all the force moves across the flashlight sideways and won’t cause a disconnect. I mainly ride trails, but the closest trail is pretty tore up and covered in sticks/rocks from the heavy rain over the summer and it’s a non-issue. If you’re doing riding where the Q8 losing contact is an issue then the mount is surely more likely to be compromised than the batteries. I still think that snugging up the battery tube is the easiest way to make the batteries more snug though obviously not as perfect as springs on both sides.
Are you sure? Long springs or springs from both ends are necessary when you will use any from 65mm cells or 70mm cells or 72mm cells.
I think protected cells are not common with Q8, so actual length difference is just 1-2mm. Short springs from tail+thick positive ring, nothing more needed. Soldering ring over springs is not simple, also positive ring with four imr cells is not something that I want to give move abilities (yes springs are rigid but hwo knows where this spring carried ring will slide after hard tuve screwing?)
