LED drivers and Accessories you want, but don’t exist

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Jensen567
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For a lower power buck/boost I found LTC3119. Has 5A switch current, 2.5V to 18V input, 0.8V to 18V output, will run down to 0.25V after startup.

http://www.linear.com/docs/56069

Barkuti
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Sense resistors are a hurdle with regards to efficiency and power handling. MOSFET VDS feedback is a far more reasonable way of sensing. It seems that there already are some commercially available noRSENSE controllers. Look, for example, at this little beauty: LTC3785 - 10V, High Efficiency, Synchronous, No RSENSE Buck-Boost Controller

 

Cheers Smile

P.S.: that sh1t owns! 

Innocent

Mike C
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I did share some 85 firmware for boards some time ago and shared a couple of boards for it because there was interest, but the problem is that my firmware is locked to my boards. I spent quite a bit of time writing instructions so that people could use it, and in the end it turned out that no one was interested enough to actually read any of it. I totally understand that, most firmware here is compatible with boards from multiple designers, but after that I just don’t bother because it takes too much time to do write ups that hardly anyone will read.

Sure, once the boost circuit discussed here is tested, I can attempt to make a two layer version in Eagle with the vias. If I succeed I can share it with some basic firmware, but as I only work with the 1634 and assign pins to my liking, I kind of have a feeling that a Bistro compatible 25 version will be much more of interest to the community.

In terms of new chips, I think there are a few that are waiting on the 1616 and/or 1617. I didn’t want to wait. They aren’t easily available to me, no AVRDUDE support and higher pin density than the 4×4mm 20 pin package. The 1634 is available, package size is as small as I want to go, 16KB programming space, AVRDUDE support, 17 usable I/Os and has 0.1 uA parasitic drain in power down sleep mode. That’s all I’m interested in really. I don’t use the Full Duplex USARTs, QTouch, I2C interfaces and all that other stuff. If anyone wants some help migrating to it, I’m here, but for my own boards and firmware I’ll just carry on as usual.

Flashy Mike
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@ Mike C:
Hi Mike,
would you mind to share the best drill size of the vias for your programming wires?
I’m currently designing my first flashlight board and intend to use this technique if my additional attempt with pogo pins doesn’t work as expected.

Mike C
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Flashy Mike wrote:
would you mind to share the best drill size of the vias for your programming wires?

I’m using 0.9. I had 0.8 before but sometimes via sizes are not exact in OSH Park fabrication, so on some boards 0.8 was too tight. Note that I might not be using the same pins as you. I got some pins I bought from Fasttech that work but wanted longer so I’m also using cut up copper paper clips.

0.9 can be a bit loose, so I have to take care when flashing. I’ve bricked a few MCUs on driver boards because of glitches when flashing. Now I use a development board for firmware development where I have soldered on the connections, and when flashing actual driver boards I’m very careful to test the connection multiple times before actually flashing. I don’t have room for those 3×2 connectors, so this is how I do it.

Flashy Mike
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Thanks!
I’m designing a Q8/SRK board, so there is space for a 6×1 row of connector pads. Found some info about pogo pin board design and will try this also.

http://blog.spitzenpfeil.org/wordpress/2013/11/12/the-pogo-key-1-27mm-av...
https://easyeda.com/feather/ispogo-oA5nFXR93

Mike C
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I had a similar idea but a round one that would match up the vias on my 17mm boards, but for each new design they change places so I just skipped it. For a SRK sized board it’ll work fine.

Flintrock
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Funny asking about Vds control (to regulate normal FET drivers) was my almost my first post here, got a lot of negative reaction. Some of that was about software though, which I get now (although easy enough on bigger chips). There's also sensefets, which is a little different I guess. FM I don't know what you're designing, but there is a buck design for SRK already, never tested though.  It's slightly degraded by the controller needing PFET's, but it should still hopefully put out 12A to 15A at 6V or maybe even 12.  That's a bunch of power.

Jensen567
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So Flintrock, you have a version of Bistro-HD that will run on the MP3431 driver Schoki made? This is very exciting to me. As cool as the Narsil ramping is, I ended up changing my Narsil flashed TA driver back to standard mode groups in my Convoy L6, I found that I never really used ramping and appreciated having a few set modes more.

Personally I think between 3 and 5 modes is about right, 3 if just L-M-H, 4 or 5 if there will be a ML, Turbo, or both.

High should be set as the maximum continuous output the light can sustain thermally, with low and medium appropriately spaced based on that. Moonlight should be about as low as the driver can handle with turbo as high as the emitter or driver can handle.

Does Bistro-HD have temperature compensation built in? On my drivers I have a thermistor mounted on the driver PCB and one remote mounted on the MCPCB and would like to use both of those to automatically ramp down the output at set temperature limits.

I’d also like to potentially ramp down the output based on battery level at the bottom of discharge rather than just a hard cutoff.

Flintrock
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Not sure what an M3431 is  honestly.  Is that the boost IC?  He asked about a firmware for this board shown on the last page or so, using an attiny25.  Yeah, I have a firmware config that should work fine on that assuming the hardware is up to the task of OTSM at those low voltages.

 

I have simplified temp compensation in HD (although it can be reconfigured easily for the old way) so that it just steps down to a sustainable level if it gets to hot.  No attempt to regulate (previously not well usually).  You can instantly tap and get a 10 second extension, but the idea is that you set the temp threshold really at a safety level, so you wouldn't want to, but it's only 10 sec.  You can also wait for  it to cool a little and tap and get more than 10 seconds, until it gets too hot again.  Or of course can tap twice and click out to another mode entirely.

 

Voltage control is the same as original bistro.  It's pretty dynamic.  Yes, if high current pulls down the voltage, that will cause it to ramp down to a lower current.  I'm not sure how well this stabilizes in practice, haven't done much testing with it.  Feedback is always a very tricky thing to really nail down.

 

I tend to agree, a few modes is fine for me, and having some idea of power output is also useful.

I'm not that keen on doing ramping, but it could happen possibly, eventually.  Who knows.  TK already has that I think.  HD is just really easy to configure for many different board configurations.

 

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I’m wanting to build a phatlight so a high amp driver would be nice 9a+

The_Driver
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Lights-Out wrote:
I’m wanting to build a phatlight so a high amp driver would be nice 9a+

Those already exist:

http://budgetlightforum.com/node/48616

https://pcb-components.de/led-abwaertswandler-buck-step-down/ampere-5000...

Flintrock
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Well that first one is a complicated example.  That's >9A at 12V even. not quite sure I'd say it "exists" either.  Nobody made it yet as far as I know.  But just the basic stock Q8 driver does 20A at 4.2V. 

 

Not sure what's with the guy grumping about driver design being uneccessary on a forum where people design drivers.

Flintrock
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NightHike before you get a 6G toaster driver, maybe you can try to fit code to regulate output of low voltage emitters that works on people's existing attiny25 boards so they can use the latest LED's without frying them.  Is that too easy for you or too Oracle?

Flintrock
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@Jensen, so yeah, the MP3431 is the boost IC.  You don't run firmware on it.  It has an MCU controller, the qfn attiny25 in this case, and yeah, bistro-HD runs on that, with a trial configuration for that board ready.

Mike C
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NightHike wrote:
Evolving doesn’t mean progress in term of improvement.

But here it does. Think about it.
Flashy Mike
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Can somebody tell how many vias from one board side to the other I need for a given current? Which diameter?

Lexel
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Schoki wrote:
Yes, the 20M1 package, but I use the tiny25v, and they seem to be rev E and F (85°C and 125°C versions) at mouser

Just wondering if you order the 25V then on your board is the diode after the LDO missing for OTSM

Schoki
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It doesn’t need a diode if you get the right LDO. I have the TPS706, which has a lower reverse current than some diodes (10nA out of IN pin, 100nA flowing into OUT pin). Here’s the datasheet: Datasheet TPS706

And for the current per via, there are some websites, just google it. I used roughly 1A per 10mil via on the plus side.

Flintrock
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Yeah, you have to check diode current when hot, not the quick-spec sheet, as it can be wildly different (exponential with temperature).  The plots look like about 2uA.  That should be good.

 

I just posted 1.7.1 of Bistro HD.  http://budgetlightforum.com/node/52798

The OTSM-LDO-fetonly hex should work for your driver, although with no real moon mode solution yet (I'd prefer the hardware two-PWM channel solution to some PWM hack, but we'll see).  I guess I should compile an OTSM-debug hex for you too, but we can see how it goes.

Flashy Mike
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Schoki wrote:
And for the current per via, there are some websites, just google it. I used roughly 1A per 10mil via on the plus side.
Thanks!

Found some information meanwhile:
http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calcul...
http://circuitcalculator.com/wordpress/2006/03/12/pcb-via-calculator/
http://www.blackstick.co.uk/pcb-design-calculators/

Schoki
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Is there any interest in a board bigger than 17mm?

Jensen567
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Yes, 20mm and 22mm are sizes I use a lot. 17mm doesn’t interest me much anymore as aside from my P60 drop ins almost everything has now been bored out to accept 20mm.

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Schoki wrote:
Is there any interest in a board bigger than 17mm?

I could use a bigger one with attiny85-sized SOIC8 or flashing pads/vias for development purposes… doesn’t have to be used in an actual light, but convenient reflashing would help a lot with adding support for the hardware.

Oh, um, probably also large pads for an e-switch. Small pads break off easily when the driver is air-wired and gets moved around a lot. Again, for development purposes only.

ToyKeeper
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Mike C wrote:
Think about it…

Thinking About It.

(pic taken two weeks ago at my friend’s house)

Schoki
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So you mean some kind of development board? So doesn’t even need to be round? I would make one with bigger pads, vias (or pads as well) for flashing, some “wire loops” (don’t know the name) to get an oscilloscope connected. Maybe there’s a way for two ATTinys, 85 and 25v, and just with a switch (or a few) you could switch between the most used MCUs for different firmware. Or some kind of breakout board (like on Arduino) with one of the MCUs on it, and you could swap them.

ToyKeeper
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With older driver designs, a dev board wasn’t relevant because it had plainly exposed pins with room for a clip. It’s only on newer denser boards that it matters. But yeah, a dev version would probably help with getting code support.

Flintrock
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Once the hardware is understood well, development for this boost driver can be done on a one channel fet driver. It's just for testing the low modes and making sure that voltage control works out where the real thing could help initially as I see it.

Sirius9
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This is like a “name your wishes” thread, I like it Big Smile

So, my first wish:
- buck driver,
- up to 20-21 mm (or 17mm even better, maybe two board design)
- 8.4V input
- output for XML/XPL 3V leds
- up to 6A
- based on Tiny13A so I could load custom firmware
- 2 switches, forward clicky for on/off and electronic switch for changing modes
- from: oshpark or china (sorry, ordering from states is just too expensive)

that would be about it Smile

 

Agro
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5A Buck-boost driver for UT-02 to push this light over 500 kcd.
Reference:
http://www.candlepowerforums.com/vb/showthread.php?440679-NEW-WORLD-ORDER-4-THROW-V54-World-that-is-HaHa*&p=5161053#post5161053

ADDED:
I haven’t measured if it fits, but buck from 2×26350 may do too. Wink

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