Driver Info: HX-1175b & HX-1175B1 (Pic Heavy)

Flashlight Modding and DIY Parts
192

Good call ohaya. Looks like the pinouts match to me - so it’s one of the μPD78F920x. Timer output for PWM on Pin 1, GND and Vdd on 3 & 4, and analog input on 6. That’s all the functions ImA4Wheelr described.

I guess the next question is whether we know anybody who can tell us about flashing these things cheaply.

EDIT: Datasheet link

193

You all might ping Dr.Jones, to see if he has any firmware that’ll work, but although I only looked briefly, these chips look pretty proprietary, from the old NEC days.

194

Meh, I’m not actually interested enough mysef. This is the only halfway decent driver I’m aware of which uses this MCU, although IIRC we’ve seen it on at least one other driver, I think it was a DD driver.

Good find on the actual MCU, now we can safely ignore it. :wink: :smiley:

195

I have [finally!] ordered two of these HX-1175b drivers. :slight_smile:

196

Has anyone tried this driver with the XHP70 (6 volt configuration) yet?

Since RMM has done a lot of measuring and experimenting with this driver using MT-G2, I'm hoping he wil drop in with some input. Buck drivers are supposed to have less ripple when supply voltage is closer to Vf. Did the voltage spikes with 3S cells and one MT-G2 appear potentially problematic for XHP70?

197

No problems with the XHP70. I've only tried up to about 8A with one, but it can handle it just fine. Even with a huge 20% ripple (this one is generally 10% or less) you're still under 10A, which the XHP70 can handle easily.

I really need to update some of my findings in this thread. I got the ripple down to a minimum, but it was around the same time that the new XM-L2s started coming out, so even though the ripple was negligible (~1%) it would still blow them at 7A, because even direct drive the LEDs couldn't handle 7A anymore. I turned them down to 6A and all was good.

198

Thank you RMM. Good to hear that. I was expecting a different answer based on you earlier reports in this thread.

I really want to design a board with a different MCU that is loosely designed like this board, but I'm still early in the learning curve for Eagle. If you ever go down that path, I would like to try to help with testing. High current bucks are what I am always interested in.

199

I've been focusing mainly on the small ones and have learned a ton since I started fumbling with this one a year ago. The cheapest route would probably be to just downsize this board then use these for donor parts. Buying good parts individually will end up costing more than what you can buy these boards for! If your goal is to power MT-G2 and XHPs then you have a lot of wiggle room when it comes to the output waveform, but if you are planning on the smaller 3V LEDs then things have to be good to go.

If you are looking at designing one, then I would recommend reading some of the datasheets, especially the TI datasheets, regarding circuit layout. When you start getting into bigger switching converters at higher switching frequencies layout matters a lot--you can't just hook the wires up and expect it to work correctly.

200

Was playing around with LVP on this driver a couple weeks ago with what appears to be some success on my PS, but that PS is cheap and gives weird results. Using 100K and 5.1K resistors and I don't remember the numbers I used in Star Momentary with 4S cells driving an MT-G2.

Need to test with cells. Been running with 4S cells since I put the light together then, but they still have not drained enough. I'll report back when I have more info.

RMM,

Back in Post 153, you had some great info about ripple and you sound like you have learned more about modding this driver since then. Hope you don't mind a couple questions, if you have the time to respond:

  • When you refer to output caps, do you mean just across the LED Leads?
  • Regarding inductor positioning and shielding, do you know if one can get some limited shielding using aluminum foil or something between the Leads and the inductor? No biggie if you don't know, I will be googling it soon.
  • Do you have any update suggestions for this driver?

EDIT: I accidentally connected a stock HX-1175b to 2S XM-L's on copper last night with 3S cells. The emitters fried instantly.

201

I've got a lot more understanding now than I did last year so I would have to revise some of my earlier statements. I had lucked into a few things working, which means that they do work, but it doesn't mean that they were ideal. I definitely don't recommend anyone using a 47uH inductor on one of these unless you want a 1A to 2A output. You want something more like 8uH-15uH for the ~6A I was shooting for.

Some of my initial issues were due to overcurrent, plain and simple. I started playing with these at the same time that the vF on the XM-L2s started to change, lowering the maximum current significantly (You used to be able to get 7A out of most of them---now you are lucky to get a lot of them to survive at 6A).

  • Output caps: Yes, across the LED leads. This will greatly decrease the output ripple current while maintaining the same inductor ripple current. This is where you always put the capacitor(s) on a hysteretic constant current buck driver like this one, which uses the QX9920 IC, but it also applies to the MAX16820. You have to look not only at the capacity and overall ESR of the capacitor, but you also have to look at the ESR at a particular frequency. Generally, smaller capacitors are more effective at higher frequencies, while bigger capacitors are more effective at lower frequencies. Putting too much capacitance or high ESR capacitors across the terminals can actually increase output ripple (and will also decrease the dimming range). With an MT-G2 I wouldn't worry too much about adding anything, since it is a tough LED to kill. With an XM-L2 you can probably eek a bit more out of one without frying it, but they are still current limited. If you're using ceramics, I'd go with a 0.1uF and 1uF ceramic capacitor (you probably already have some 1uF capacitors laying around). You can parallel more capacitors up to a point, but the gain diminishes quickly.
  • I'm not sure about the inductor shielding. I'm not sure if foil is a good idea. On mine I was just putting some heat shrink tubing over the inductor to keep the wires physically farther away from it, but that isn't the same thing as really shielding the inductor.
  • If you are looking at changing inductors, I would use the formula from the TI datasheets or the the Maxim datasheets to determine what your switching frequency ends up at. You have some wiggle room with the factory inductor.

This is still a heck of a beefy driver for the money. It is easy to piggyback onto and can handle a lot of current. You can turn the output down a bit by changing the sense resistors (I=0.25/R). The main downside to this driver is that it is hard to turn into a good momentary driver due to the high quiescent current drain. You couldn't buy the parts to build one of these for the price you get these for, so they're still a sweet deal.

202

^ Thank you for more great info. Very helpful. I won't pretend to understand everything you said as you went deeper than my electronics knowledge base. I will be googling and trying to learn the stuff I don't understand. Nothing like a real world problem/challenge to encourage learning theory.

I've made about a half dozen lights with this driver and all of them are momentary switches. Definitely have to use discipline locking them out. All the drain appears to be in the up front voltage regulation that feeds the MCU and part of the buck converter. It's a very common system using diodes that seems to be in every buck driver I have encountered. Is that something you have addressed in your buck drivers that you are developing?

203

Hi,

does anyone has a schematic of this driver HX-1175B1?

204

I'll look for my notes, but can't promise anything. I know I scribbled one out a long time ago, but I never go around to verifying it. It's hard to see the traces with the large copper traces on the battery side.

205

I have prepared one in easyeda and it is more or less I can see under the light and by the use of my digital multimeter, so I can share it to work it out together.

206

Sure. I can PM you my email address. Do you use Eagle? IIRC, I designed a 20mm and maybe a 17mm version of this buck. I designed it to use the parts from the HX-1175, but with a LDO voltage regulator to feed the MCU and Buck Converter. I never verified that the design would work though. I should have the schematics for those in Eagle format. If you want, I can send you those files.

207

Thanks, email sent over to you. In general I use EasyEDA but I will manage Eagle as well.

208

^

I tried to find my Eagle files on the above boards last night. Apparently, I have changed computers at least once since I last touched them and did not pull over my Eagle files. Fortunately, I still have my previous 2 computers. I just need to dig them up. I will search their drives tonight. I sure hope I find them because I put a lot of work into those boards.

I'm not familiar with the program you mention above. Is there a free version of it available for download? Or at least just a viewer?

EDIT: Googled it. On-line and free. Cool. Take a look at your schematic and get back to you.

EDIT2: Just enough time for a casual observation for now. I don't know if your schematic need to have the same physical lay out as reality. If it does, Pins VDD and CS need to be swapped but connected as you show in your diagam (i.e. CS to R101 and VDD to C2 and the diode labled "S4" that goes to regulated 5v voltage regulation.

209

A couple other notes:

  • I think R7 should be 30K resistor.
  • R6 is 330ohm on my driver. Does your have 470ohm?
  • Some drivers have a capacitor instead of a resister at R7 (see pic below).
  • R2 and R3 should be .068ohms

Hopefully, I find my Eagle files tonight.

EDIT: Added 4th bullet.

210

Just in case I can't file my Eagle Files. This should be close to how wired (except no MCU in below diagram) the boards I mentioned above.

The LM2936 is rather large. So I just use the TO-92 package. You don't have to have designated pads that way. Just run the legs to pads already on the board. Oriented sideways, it should be no taller than a through-hole inductor. I'm sure there are better voltage regulators, but I'm just comfortable with the LM2936. I have a thread on it here.

211

ImA4Wheelr, thank you for your comments. You are right about R2 and R3, they should be 68 mOhm and R7 is 30k, just typo. R7 is 470 on my driver.

EasyEDA is easy indeed to use btw.