The Texas Buck driver series, Q8 / Skyray King 2S/4S buck driver RELEASED!

I honestly do not know what reference is used but I would plan on using the 1.1V reference since the firmware is already setup for that IIRC. I am guessing 4x the resistance should be roughly correct for 4x the voltage.

The 19.1x vs 22k doesn’t make a big difference but it is noticeable as about an extra .5-1 second for the long click to activate. It can be recalibrated for the 22k naturally but it ends up right at the very edge of the range.

19.1k puts it closer to the upper middle of the range which is nicer to work with.

All calibration is done before compiling the firmware.

We built the first FET drivers based on the Qlite 3.04A design and board. It used 19.1 and 4.7K resistors for the LVP. We still use those, for the most part, as they’re commonly available and many of us that bought parts bought by the 100’s for price reduction. So now when we build new drivers, we use the components at hand that are proven to work. No need to rethink something that’s been working for years.

I and some others started using a 22K so we could use an 8.4V 2 cell system with the Zener modification to 6V drivers, mainly, then, the MT-G2. Along came the XHP-70 and 50, and things are taking off. Mostly though, the off time cap works well with the 19.1/4.7K setup, so it hasn’t been modified for consistency reasons.

I’ve built HUNDREDS of these drivers, have quite a few more FET boards and a fair stock of most components. So that’s how it comes to be historical baggage. Comfychair started putting an Vishay 70N02 MOSFET on the Qlite board, replacing the 7135 chips, even flipping the huge MOSFET upside down to make it work. I was amongst those that implemented this at the time, and a lot of others picked it up. Wight started designing new boards, along with MattAus and several others, I found the SIR800DP through hours of eyeballing charts on DigiKey and Mouser, and here we are.

For the record, we had to keep numbers in the ATTiny13A firmware under 255, so the 22K was about the highest value we could use at 245 to keep the LVP with 8.4V cells. I would use 124/112 settings with an 3V emitter, 245/228 with 8.4V set-ups.

It might be of some importance to note that Wight designed but didn’t really build the drivers. He’d put the new designs up on OshPark and let us flesh em out. I went through quite a few revisions this way. And MattAus got so burned out designing for the hot steady flow of requests that he dropped out of the forum altogether. He was a critical component to these FET drivers when it all took off. Wight has been gone as well, for the most part. So our teams that designed and tested have fallen apart under the stress of the rapid growth and of course, they had jobs. MattAus is an Aerospace Engineer working at an airport, not sure about Wight.

Yes, some of the builds didn’t work well, like the Knucklehead. I still have a box of components from building those, to no avail.

I guess some people around here think I got 13000 posts by saying things like hey, cool light! hahaha
We went back and forth at an amazing pace, for quite a while, just like you guys are doing in this thread.
That, and of course, I talk too much.

LOL, I had over 30k posts on one forum and over 20k on another plus over 10k on a few more. Few people talk as much as I used to.

When I take on a new hobby/forum I tend to go all the way in. Flesh out everything I can do in that hobby and then when there is nothing left or something else is more interesting I move onto something new.

Part of why I want to make sure I finish all these projects I have been working on before I find something new to do.

We used to have Scaru breaking new ground with multi emitters before anyone else did it, ChicagoX was making big lights, light bars, designing boards, way back before FET drivers. OL was building MagLites, filing his mark on the tubes and random finishes. The forum has changed a LOT since I came in over 3 years ago. We’ve lost a lot of good folks too. Foy used to be hilarious withhiswayofrunningwordstogethersigningoff. Some of the big group buys brought a lot of people in from other sites, which changed the face of this forum as well.

Now The Miller is breaking new ground, as is TomE and Pilotdog68. I’m still just a hack slamming lights together to find out what they do before the magic smoke appears…

Yeah, I get it. It works and stuck. Again, not criticicizing, just like to understand what's needed and what is just established and why. After all we are making some changes anyway probably, particularly the ldo voltage, so I can't just assume that won't have any effects. Now though I know, we aren't referencing of LDO (but I think not 1.1 either).

22 is a bit different from 19.1 (about 15% different OTC times). My point was more why not 20. I suppose people will need to order an LM3409 anyway, so adding a non-standard resistor value to the order doesn't really matter in the end. It's just a funny number. That's all, especially since almost all the rest are standard values.

At TA, yeah, 1.1 won't work without much higher resistance values than we're discussing. 2.55V (2.56 I think but whatever) is right as DB says (thanks for that feedback DB), and anyway, yeah, it's not vcc so that's the main thing because that's what I changed and wanted to make sure wouldn't impact anything. So 36K has worked and we'll use it.

Just for the record,
22k was introduced when driver boards were created where R1 was changed to a position before the diode D1. This allowed for more precise voltage measuring (while introducing OTC timing problems…).
22k instead of 19k1 compensated for the loss of the ~0.25V drop over D1, so existing firmware (mainly STAR back then) could be used on these newer drivers while maintaining the same LVP voltages.
Those were the days… :slight_smile:

You make me feel pretty old talking as if 3 years ago was a long time. But it was a bunch of work put in clearly.

Yes, and it was a lot of try and error, some dead ends… and a lot of fun. Just like today, really. :slight_smile:
It’s just that in these years BLF as a whole has developed an incredible base of hardware and firmware. And it still moves on.

To me some weird historical baggage is how the E48 and E96 series don't include the E24. Sure you can get 2% spacing with fewer resistors by starting over, but then you still ALSO need the E24 resistor values on hand anyway(if you want to be stocked up), so it's actually more in the end. I suppose it makes sure nobody accidentally uses 10% resistors when 1% is needed. In practice it doesn't really work out that way since 1% tolerance E12/24 values still get used at least as often as not, probably because people don't have to look them up. How often do you see a 1% 47.5 specced? Probably almost as often as a 48.7, but not nearly as often as a 47.0.

Wow! What did I say in here that earned me a rude mark?

It certainly wasn't me.. or not unless I clicked something by accident (that could be possible). Anyway, we're cool as far as I know.

WHAT? :open_mouth: :frowning: :person_facepalming:

So about C1, it turns out it does want to be bigger, for the same reason many of the caps do, 4S, high voltage. I forgot that C1 is full voltage. In 0805 10uF ceramic or Ta, there are no x7R caps over 16V on digikey at least. Best I can do is a $0.57 cent 25V X7S ceramic. That should probably work for such a light load, on the other hand the cap is right next to the inductor pad. The 1206's are $0.20 in bulk, and basically one more is free if only making one driver anyway. So yeah, we can probably make due with an 0805, but ideally, it's specced as 1206.

I am not sure what all the rude clicking is about. The only one I have got was a post that everyone agreed was not rude. I just ignored it as someone having a bad day.

I will see what I can do when I rearrange things. I would not hold out high hopes though, it is really tight over there and DEL likes to see the traces as short as possible for all the MCU power leads.

Got the shopping cart almost done. This is going to be expensive. Heck it might be more fun designing it than buying it. ..yeah, looking like about $22 plus the board of course. Ouch.

Yeah, I kinda got that sense fairly early on. Glad to have it as an option but not real practical to actually use for most lights.

This is why I have been reconsidering making an op-amp driver. Not as efficient but a heck of a lot simpler, easier and cheaper.

I just have not had a lot of luck picking out an actual op-amp IC with which to start such a build.