Buck and Boost Drivers, Testing, Modding, and Discussion (Pic Heavy)

If new firmware is written it would not be too hard to wire any mcu to the existing circuit using breakout board and hard wiring that board into the circuit.

Yes, would be nice to avoid that an just be able to have the MCU properly soldered to the board, though. Putting something like an ATTiny45 on the board would not be too difficult, only a few traces to modify and re-route. May not be worth the time when RMM is releasing his own version soon though.

As for my own designed driver and MCU selection, I think I will go for the Tiny1616 even though it does not have great availability yet. Digikey does have ~1500 in stock, and the MP3429 IC is not readily available yet anyway. I/O wise I probably only need about 4 pins, so any of the newer QFN chips is overkill, I would do a super tiny QFN12 if they had it.

I don’t plan to commercialize it, but with the MP3429 IC hot air or reflow oven is a requirement to solder it anyway, so going with similarly difficult peripheral devices is not a big deal IMO. Keeping it smaller is a bigger priority for me. I’m shooting for a 17mm version, with 20, 22, 30, 32 all available, and better heat sinking for the IC as size goes up.

One thing to think about, you may not need more in out pins right now but revisions and advancements in the future would be possible with more pin options.

The 20 pin QFN package should give more than enough future expandability. I have thought about future development, part of the reason I decided I will stick with the 1616, I want to use the newest generation of MCU I can. Really I would love to go with an MSP430, but I want to take advantage of all the great work the UI gurus have put in, so will stick with ATTiny.

:+1:

Here is the H2-C Schematic for anyone who was waiting.

Here is the first revision of a schematic for my own boost driver. I decided to go with the MP3431 instead of the MP3429. They are basically the same chip but the MP3431 has an optional input current limit pin if we want to set a limit below the 21A switch limit.

I’d like others to look over the MCU circuitry and see if I am missing any critical features we might want. Right now I have included both a driver mounted thermistor and a port for an external thermistor, as well as a port for a momentary switch. Then we just have battery voltage input. Once I get the schematic mostly finalized I will start trying to lay out the PCB.

I hope you are able to complete this project successfully. There is a need to advance the hardware of BLF drivers to catch up to the wonderful firmware available. Unfortunately this wonderful firmware is limited to mostly linear drivers at this point in time.

In your schematic you have an ntc resistor as well as ntc resistor port. Will this give the firmware two separate thermal data points to control temp? Or just one or the other?

Hardware will support both, so really it’s up to the software. Supporting both at once was the plan though, at 20A input current the IC will be shedding a lot of heat so driver temp may become important.

Very nice! I just had this image in my head of a graph charted and recorded by an MCU. Then able to load that information back to a computer for easy observation of heat flow. Or an MCU in calibration mode that monitors the heat flow on any given level and calculates the best thermal performance for that particular setup.

Edit: After reading this, it sounds the same as what BLF firmware is already doing. However, it’s different in my head anyway. Maybe just more detailed and more complicated than needed. :person_facepalming:

Noob question :

The lower resistance the sense resistor is the higher the output ?.

I was changing the emitter in my C8S and damaged the sense resistor, I don’t have a R025 but I have a R018 but I think that’s a to low value making the driver over heat?

Correct. R018 may be a bit too low unless you have a good thermal connection between the driver and the host.

Thanks for the fast reply.

I went ahead and changed the resistor to R018 and the driver works :smiley: .

It steps down fast and starts to blink, but at least it works. I don’t know if I damaged something else when I shorted the reflector but I will try to find a higher value resistor and see how that works out.

Just the fact that I made it work again I consider a victory I am more of a solder two wires kind of guy.

hi, i am using the KX70 32mm “6V” Boost driver in a courui d1 with a xhp50.2, powering from some good keeppower protected batteries, and notice often that something shuts down the flashlight in middle of using it. it would require me to remove the battery to restart it. it seems like the batteries are going short or something in the driver is failing, have you observed this?

I have not experienced that on any of my samples no. What current is the protection rated for? The driver can pull up to 10 amps from the cells depending on output and charge level.

solRNY, protection circuits are an additional hurdle which reduces a cell's discharge performance. Your protected KeepPowers are more than likely low drain cells with standard discharge protection circuitries, causing additional output voltage sag. The equivalent series resistance in one of those protected batteries is equal to the internal resistance of its low drain cell (high, above 50-60mΩ) plus the resistance of the probably two 8205A MOSFETs (close to 15mΩ) which switch the cell's cathode. This is very high and completely inadequate for even remotely close to high drain applications.

A high drain cell's internal resistance is generally well below 30mΩ. Mooch, the vaper's community reviewer, concluded that low drain cells are only worth it at up to half of its rated maximum discharge current (or so) versus the 2800-3000mAh high drainers. It can be argued that the test's cutoff value is very high (3.2V) and I agree, but anyway it serves as an enlightening reference: Which High Capacity 18650 is the Best? -- Shootout Bench Test Results @ E-CigaretteForum

V1 posted on Thu, 08/10/2017 - 15:17; redundancy typo fixed.

thanks for the battery education. I will use high drain unprotected cells.

0K my technical fellows, just found this lost beauty (I hope): CF FX-17A 17mm 3V - 9V 2.2A 1 cell or 2 cells 2 Groups 3 to 5-Mode Driver Circuit Board @ Kaidomain

No relevant information found for the driver. My observations:

  • Reverse polarity protected. As Jensen567 explained in this same thread some messages ago for the H1-A, this means the driver innards' ground plane is isolated from the host, which is heat transfer detrimental.
  • Amount of modes and spacing: 5-40-100%, with optional strobe and SOS. :THUMBS-UP:
  • Last used mode memory, 3 seconds. :THUMBS-UP:
  • Stock output is 2.2A, sense resistor :facepalm: 0.1Ω , 0.22V sense voltage. This is inefficient, a lot of power is lost here.
  • Height is listed as 8mm, spring excluded I believe.

Sheesh!

It's 17mm, but wrong in every other aspect. An LD-29 beats it hands down.

Cheers

I have a couple of those on the way already actually. Im guessing it is QX9920 based but will find out. Plan to use them in some converted mini-mag triples, so not going to push much current.

Mmmkay fellows, finally found and opted for this “host” of my liking: ThorFire TA13 (Sofirn SF30?) questions

Excellent driver boot in there, doesn't it? It probably is the better zoomie flashlight for modding one can buy in that price range. ;-)

Not gonna mod it straight yet, looks nice, no hurry. I'll buy parts as I can slip €urobucks for it, economy is tight now so we'll see.

Cheers