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

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Flintrock
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I guess in the end it's not actually the high voltage that lets me get power out of pannies.  Well yes and no. A given current through the leds requries the same current per cell however you stack them.  But voltage sag doesn't limit the current draw this way, neither sag due to high current, nor "sag" of partially depleted batteries.  It just lets you push them harder.  That part is really true of a boost converter too I suppose.  

  

RMM
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Anyone try this yet?  I've been absentee here on BLF for a while, but I'm leaving "work" behind over Christmas break and am catching up on some reading around here.  

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Texas_Ace
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RMM wrote:

Anyone try this yet?  I’ve been absentee here on BLF for a while, but I’m leaving “work” behind over Christmas break and am catching up on some reading around here.  

Not that I know of, I simply do not have the money to try it myself but would love to hear if someone else has given it a go!

RMM
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Texas_Ace wrote:
RMM wrote:

Anyone try this yet?  I've been absentee here on BLF for a while, but I'm leaving "work" behind over Christmas break and am catching up on some reading around here.  

Not that I know of, I simply do not have the money to try it myself but would love to hear if someone else has given it a go!

What is the estimated cost per driver?  

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Texas_Ace
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RMM wrote:

Texas_Ace wrote:
RMM wrote:

Anyone try this yet?  I’ve been absentee here on BLF for a while, but I’m leaving “work” behind over Christmas break and am catching up on some reading around here.  


Not that I know of, I simply do not have the money to try it myself but would love to hear if someone else has given it a go!

What is the estimated cost per driver?  

Excluding the PCB cost (which is about $1.50 each if you order from china, but you have to buy 10 of them) the parts look to be a bit under $20 from Arrow. Although the FET is not available from arrow and we never got around to finding one that was. From digikey it was like $23 total.

Hikelite
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I was thinking could I have more than 1 of these buck converters going from the same MCU like an ATtiny84 which has more I/O pins available.
What do you think? Host and size would not be an issue for me.

Texas_Ace
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I suppose you could but it would be one ugly setup, better to run either a custom made driver for the job or run multiples as they are IMO.

Plus running buck converters in parallel can be interesting, they generally do not share the load evenly and take up more space then simply making a larger buck to start with.

Hikelite
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I see.
Well I wanted around 450W output from 12*18650 in a custom host. I have not seen a converter of that magnitude (450W output) that and that can also be PWM-ed with a
high frequency for a custom UI.

Texas_Ace
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With that much power output I am afrid you are looking at 1 of 2 options.

A: Get a pre-made buck converter, there are lots on ebay and design your light to fit it. Then use a simply externally mounted pot (or possibly magnetic ring) to adjust brightness. This is simple, cheap and effective.

B: Go with a completely custom made buck driver that will cost a lot in time and cash just to get a UI.

With a light that powerful and large I am not sure that a UI would be much more useful then a simply pot knob? Not like you are just going to be tossing that in your back pocket! lol.

Flintrock
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This is a current regulated buck regulator.  I don't see much issue with it sharing load.  Voltage regulated ones probably won't share well.  To share control you could just split out the connection from Cf2 to iadj.  So you could possibly make a few boards, only populate the mcu on one, and pull off a wire from that cap to the others. 

 

 

It might (not sure) be more sensible to think about beefing up the components and cooling,  or, yeah, just buying a buck made for it, with a sufficient heat sink, and use a pot to control it as TA said.  That would surely be cheaper and easier.

RMM
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450W is some serious business...that means either extreme amps or high voltage.  High voltage gets you there with a much smaller and efficient converter---one that could actually fit in a light, but even if you went with something crazy like 12S you'd be at ~10A, but at 40V+ you've got other issues to deal with.  Not impossible, but not something to be taken lightly.  A short circuit in a light like that could have disastrous consequences. 

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Flintrock
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Update on that cheap $5 analog  current/voltage controlled buck from a page or so back.   The current control suddenly went out just while running almost untouched (mild movement of the whole setup) at about 18W throughput. Fortunately I had set a voltage limit that cut in just a tad higher or I would have destroyed four nice LEDs.  Turned out one of the knock-off-branded copies of bourns trimpots just quit and failed in the wrong direction.  It couldn't be set after that either.  The screw did nothing.  I tested with an ohm-meter to be sure.  While testing though I was pretty sure I also managed to fry the op-amp it was connected to.  No big deal since I was going to be ordering parts anyway.  I replaced the pots and the op-amp at the same time just to be sure, and all works basically fine now considering the price.  It looks like many of these cheap bucks use cheap pots, so it would be worth considering to pick up some bourns pots as a planned upgrade from the start.  That makes them a bit less cheap.

 

Seems to be a bit of a case of getting what you pay for.

The_Driver
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So, has anybody built one yet?

Would it be possible to power a 3-4V Luminus emitter @15A with this driver from 2-3S batteries?

Texas_Ace
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Yes, it can do that with the right components installed. At least in theory. I am not aware of anyone that has built one yet. To build a single driver would be like $40 IIRC.

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Since there is no comparable driver on the market, 40 dollars seems ok.

Which components would I need to change and how would I go about doing that?

Did you ever program a firmware?

Texas_Ace
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I have never done anything more with this driver then what you see in this thread, just too expensive for me to mess with and I could not justify it.

FlintRock has a post explaining all the components in this driver, I think I linked it in the OP. That would be the place to look for the components.

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