6V FET Driver Issues

[kelsey]

Another firmware thread!

I put together a FET+7135 driver with the zener mod, parts from Mountain Electronics. I’ve been experimenting with different firmwares, trying them out and messing with a few of them to try to find out what I like. I think the one I like so far the best is ToyKeeper’s A6, the ability the back up modes is awesome. I got the LVP stuff with ADC values I think mostly figured out, but it is still acting strange. I think it has something to do with the OTC. I flashed the driver the ToyKeeper’s OTC checker FW, but after poring over the Readme, neither my wife nor I could figure out how to calculate values.

So when running the A6 FW, the light progresses through the modes normally if tapped quickly. I can’t get it to back up modes, nor go to moon. It also acts weird and unpredictable when tapping a medium length.

Would someone just off-hand know the values for the OTC to use in this case? Again, the parts are from RMM, just a standard FET+7135 zener.

If I need to figure out the OTC values using ToyKeeper’s method, can someone explain how to do this?

Here’s her readme:

OTC / off-time capacitor
————————————

What you’ll need:

• A metronome of some sort (preferably at 120bpm).

The process:

1. Flash offtime-cap.hex to your driver.

2. Connect a power source to your driver — one which can be easily
turned on and off (or connected and disconnected). A fully-assembled
light works well.

I normally use two alligator clips which lead to a stripped wire,
clipping one to the driver’s ground ring (the big pin on a 7135 chip
works well) and the other to the battery-side spring. At the other
end, I hold the stripped wires onto a battery.

3. Start a metronome at 120 bpm.

On many Linux-based systems, the following works:
while true ; do beep -l 10 -f 3500 ; sleep 0.5s ; done

4. Disconnect the power on a metronome tick, then reconnect on another
metronome tick. Each tick is 0.5s, so 2 seconds would be
“disconnect, tick, tick, tick, connect”.

5. Write down the value blinked out by the light.

6. Repeat the measurement several times.

7. Take an average of all the measurement values.

8. Repeat the whole measurement process for each length of time you want
to get a value for.

9. Plug the averaged value(s) in to your firmware of choice.

For example, I measured two drivers and got the following results:

Driver 1:
time - avg : list of measured values
0.5s - 240.6 : 235, 241, 241, 242, 244, 241
1.0s - 218.6 : 221, 220, 219, 217, 216
1.5s - 196.6 : 199, 196, 197, 194, 197
2.0s - 172.0 : 172, 171, 173, 172, 172
3.0s - 133.2 : 135, 131, 134, 133, 133

Driver 2:
time - avg : list of measured values
0.5s - 222.0 : 221, 220, 225, 218, 221, 227
1.0s - 175.6 : 176, 180, 173, 178, 171
1.5s - 127.2 : 134, 132, 123, 120, 129, 125
2.0s - 99.0 : 99, 100, 99, 97, 100
3.0s - 86.6 : 86, 87, 87, 87, 86

Note: If you’re using a lighted tailcap, you must do these OTC measurements
with the light fully assembled.

I’m not understanding the second part of number 3, nor number 5. What value? Sure, my light blinked a few times after powering it on and I had my metronome going at 120bpm, but what was I supposed to be writing down?

[pilotdog68]

You write down how many times the light flashes after you reapply power. The metronome is really not necessary, just disconnect power for the amount of time you want it to take to register a “short press” or whatever, then reconnect power and the light will blink out the value for you to put in your firmware.

I don’t even do this step anyways. I just put in a number (usually start around 190), then try using the light. If the ‘reset’ for the short vs medium press or whatever is too long, I just try a higher number (like 205), if the ‘reset’ is too short, I put a lower number in there (like 170).

What it is doing is measuring a relative voltage on the off-time capacitor. As the light is without power, the capacitor slowly drains, and when the light is turned back on it checks the capacitor to see how much voltage is left. From there it determines how long the light had been off, and what to do with that information (like change mode or return to the saved mode)

[kelsey]

Merci, pilotdog. Do you have any idea how and or if 6v affects this all? Because leaving the otc values alone worked fine on a single cell light on the same firmware.

[pilotdog68]

6v definitely can/will affect it, but even with a single-cell light it sometimes needs to be adjusted because of tolerances/variances in the capacitor. As some members will point out, the whole concept of the off-time capacitor is not very sound electronically, but it works just fine for flashlights…usually. TK’s short/long press stuff is more picky than other types though.

[pilotdog68]

When I program a driver, i usually put in values for things that should be close, then use the light for a few days while making a list of all the things I need to tweak. Usually the second flash ends up being close to perfect.

[kelsey]

I ended up giving up on using the A6 firmware, but I got thestar working with some code changes, including functioning LVP!

I now have a 4 mode light with a decent moon, memory, turbo timer, and DD on high! What more could I ask for? This thing has got to be pushing 4000 lumens.

However, what I find odd is that flashing the regular FET LVP didn’t kick in, but the FET+7135 it did. Not sure, maybe I need to check my resistor bridge.