A few minutes ago I finished modding my ∅17mm SST40 biscotti clone drivers, one of them will (hopefully) go in an old, modified Thrunite T20T and for this reason I removed the stock spring (there's barely place for a copper top cell driver contact inside that tiny flashlight).
So I grabbed a couple BlueSwordM's springs, 3rd and 2nd gen big springs, and proceeded to make a crude voltage drop over the spring test against the new springs Simon is using in the biscotti clone drivers. I used my precision power supply tuned at 5A, with alligator clamps attached to the ends of the springs as best as I could. Connecting at the base of the springs was easy, the top gave me some difficulties, and I placed my multimeter's probes as best as I was able (near the base beside the clamp and as close to the top as I could make a decent contact):
Newer wide top spring from Simon: in a first run I was getting 60 - 65mV. Tried two more times, got values jumping up and down up to 70 and below 60mV. On average, I give it a rough score of 62 - 63mV of drop.
BlueSwordM's 3rd gen big spring: could see some figure above 60mV, but all around 57 - 58mV give or take rough drop score.
BlueSwordM's 2nd gen big spring: this was fast, could clearly see figures settling around 45 - 46mV rough drop score. Bear in mind the 2nd gen spring has one coil less than the 3rd gen, and it somewhat deforms once compressed.
Now, despite the limitations of the test and the possible percentage of error, all I can say is the stock springs coming with the newer drivers are awesome! Let's wait to see what Simon has to say, but they must be made of C17530 or something with similar IACS conductivity to perform this good. It's either this or I did some blunder with my procedure, although I don't (yet) see how.
Phosphor bronze? I wonder, though, why it does so good conductivity wise. Or at least it did very very good in my quick test.
Excuse me Simon but the ramping driver is linear, employs the onboard MOSFET as a variable resistor by tuning the gate voltage using the voltage drop at the sense resistor to regulate. Exactly like in the other SST-40 sequential mode selection drivers.
It kinda pushes them pretty hard. My guess is that Simon goes for reliability over maximum power; same way that car manufacturers detune engines so they’re reliable. Makes sense; I’m just glad there’s a way we can do that if we want.
Thank you so much for a wonderful explanation, dear friend! :+1:
it’s good to hear Simon is now using some nice high current springs on his drivers. Hopefully he’s done the same with the tail springs.
Tell us, please: do you plan to use these beautiful springs for tail switches?
How to buy a flashlight with these beautiful springs on tail switch?
We love your flashlights very much in Japan, we even have our own little offline community, we go to the mountains with your flashlights. We love you, dear sir!
It’s very good that you are improving your flashlights in order to achieve the highest heights in your production!
If you have such a requirement, I can replace the spring for you before shipping.
∅22/20/17mm driver pictures can be found here (NTC resistor or temperature protection removal thread):
The ∅17 and ∅20mm drivers use a 1210 imperial size sense resistor (3.048 × 2.54mm theoretically). The ∅22mm driver uses a bigger chip resistor, and can be clearly seen that it must be a 2010 imperial (a 2512 looks like it would fit, though).