Is there a pad under the driver for a spring bypass? In that photo it looks a bit like the hole on TA drivers, but the other photos show components on the top side.
Small pad in the center skinny_tie, it can be clearly seen in the photo. The coil gap at the bottom of the spring has usually been my most successful place to stick an upwards coiled wire as bypass, I must say.
I don't see a problem zeremefico, the ∅17/22mm weird firmware ramping driver features somewhat better hardware and outputs close to 8A of current to the emitter(s) using just below 40mV sense voltage. What you observe is to be expected.
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.
Thanks for the tests! I’m really not keen on spring bypasses so 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.
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.
Simon, can I PM you my order number to extend the Buyer Protection? I thought I sent a request through AE but don’t know if it got there; apparently my order will “close” in 2 days.
So 0.05V with say, R020 (0.02 Ohms), shows as 2.5A. If you solder an R020 resistor in parallel onto the R010, it’ll give an output of 7.5A (or around it). R025 would give a total of 7A, etc etc.
The issue is getting the exact size of resistor or at least close to it, and a pack with different resistances!
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.