Bleeder resistor help and theory of operation

amars7 · 2019-04-11T01:37:24.000Z

I know there are a dozen of these threads already and I've looked through all I could find without finding any real answers. I am trying to add a lighted tail switch from Simon's aliexpress store to an S8 with a Biscotti driver. I have tried bleeder values from 180 ohms all the way up to 68k ohms. Well, I skipped a few values between 15k and 68k, but you get what I'm saying.

The worst part is, I originally had settled on a 4.7k ohm value as when I was screwing with it all hooked up with aligator clips, that value seemed to work. When I soldered it it place and reassembled the light, I got no mode change at all, permanent first level, no entry into config, etc. Took it back apart and played with values some more, now I can't get any values that get past the "next mode memory" issue. Every value behaves the same, none of them work.

Everything I read says vague stuff like "it just depends" or "could be anything from x to y" but at this point I'm really curious to know what specifically causes this issue, and how does the bleeder solve it? If I had a handle on that, like at a hardware level, I feel I could make something work here. I'm guessing it has to do with both Vf of the tail switch LEDs and the value of their series resistors, as well as the driver's mechanism for counting time, something about a capacitor, right? Is the cap emptying too slowly?

Any insight into this system, and any ideas on how to more accurately determine a bleeder value, both greatly appreciated!

MyRants · 2019-04-19T02:37:41.000Z

x2

gchart · 2019-04-19T03:08:21.000Z

On these Convoy / nanjg105c / Qlite drivers, I pretty much exclusively use 750 Ohm resistors. Never really had a problem with them.

amars7 · 2019-04-27T17:38:49.000Z

I’ve tried 680 and 810, would it be that sensitive?

gchart · 2019-04-27T17:57:37.000Z

There’s a couple styles of this driver. There’s one that Simon ships with Biscotti that I’ve never had good luck with. Not saying it’s impossible, I just haven’t had any success.

The ones I prefer are the nanjg105c style (the “star” driver, had 4 stars on the spring side). The other kind is the FX-12 driver, the 4x 7135’s on the spring side are equally spaced out (90° in between each).

Is yours the FX-12 style?

djozz · 2019-04-27T18:58:59.000Z

I never got the lighted tail to work with a biscotti driver, so your results match that.

The easiest driver for a lighted tail is in my experience the BLF-A6 driver, it works with many bleeder and tail resistor values.

One thing that can still make a difference is increasing the resistance in the tail, but doing that the tail leds become dimmer and dimmer and eventually may be too dim once the driver starts working properly.

gchart · 2019-04-27T19:03:50.000Z

Yup, easiest fix is the A6 driver if you’re up for FET+1. If you want to stick with linear, grab a Qlite from Richard or Hank. Other places (Fasttech, eg) carries the nanjg105c but then you’d lose the great firmware unless you’re down for flashing firmware.

Paradise · 2019-04-28T06:29:57.000Z

My biscotti drivers never worked with a bleeder resistor (I bought the lighted tail switches off Gearbest when they were on sale, they were only 70 ¢ after points). Problem is they don’t work with the driver I wanted to use them with.

At some point I just dropped the idea of lighted tail switches completely.

Lexel · 2019-04-28T13:38:36.000Z

My Bistro HD OTSM drivers work with any resistors as it uses no more OTCapacitor

gchart · 2019-04-28T14:04:19.000Z

Biscotti drivers also do not use an OTC.

Barkuti · 2019-04-28T15:03:51.000Z

Lothar · 2019-04-30T13:15:43.000Z

Very good thread, and I feel to a certain extent the OP’s question has been answered: Replace the Biscotti driver with either a NLite or BLF-A6 driver.

But one of his questions still remains, and I also have that question: Is the OTF cap emptying too quickly or too slowly, or too quickly with a bleeder resistor? If the OTP cap is emptying too quickly, should the bleeder resistor value be higher or lower?

Thanks