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

Sounds good. What gets hot at 10A?

I wonder whether the stock duty cycle was only 50% or ??

Nice job.

I didn't run it long enough to get it that hot, but I would guess it will be the voltage sense resistors and the large diode next to the FET.

I started working on this too late to do any testing. When I do, I will report back.

50% duty cycle, Sounds possible. I really have no clue. I need to hook up an oscilloscope to a stock driver and see what it tells me. I have one, but I still haven't learned how to use it.

Ill just answer here (instead of PM). I wasnt planning on connecting anything to the TK61 driver. I was planning on replacing the driver with HX-1175B by doing a bit of "rebuilding" inside the light.

Its really nice to see you have made this progress. Looks like there is hope for me to improve the UI now. :) Not that I have the drivers yet. Tracking never worked. Dont think they ever left China. They were just reshipped. Hopefully Ill get them without issues this time. Ive been really unlucky with trying to buy more these drivers. Hopefully Ill get the right ones.

UPDATE: The mod in this Post has a problem that will cause an over current and maybe over voltage situation. Please see the corrected mod at Post 50 below.

Sounds like a good approach RaceR86.

Not sure what to make of the high current situation. Let me walk though what I did tonight just in case there is something I'm missing.

Decided to just wire up an Attiny13A by itself because I don't have room in my UF-T90 for the Nanjg 105c driver and I don't want the redundant circuits. Wired the MCU the same as the whole driver from last night. Here are a couple pics.

Looks ugly, but there are no shorts in there. So it works just like last night. All mods work fine and 9.7 amps on high. I charged up some King Kongs and put them in. All modes work fine and with the same amperage readings for all the modes except hight. High measures 13.8 amp. I didn't leave it on to see what would happen. I should note the current readings for the other modes. These are just rough approximations of what I recall. I didn't write the currents down and didn't pay close attention to the lower modes.

PWM Current

1 Too low to realy measure. Says .01 amps sometimes

3 Same as above

9 Very low. less then .05

27 About .3 amps

100 2.2 ish amps

Pulled the voltage sense resistors to see if maybe I have a short under them. Everything looks fine. Try to use the driver with no voltage sense resistors and it doesn't work (as expected). Installed one of the stock voltage sense resistors. Al modes work fine and get the same currents as above, but the resistor fries almost instantly on high. The light seems as bright as with 2 voltage sense resistors at 13.8 amps. Driver no longer works (as expected). Replace the voltage sense resistor with the remaining stock resistor just to see if process repeats. It does. Same exact behavior. It feels like the driver is going max current even with one resistor.

It's getting pretty clear whey the HX-1175B1 has such large voltage sense resistors. They are hugh. This driver was hard on the voltage sensor resistors before my Attiny swap. They were the sole source of heat before I replaced the large diode I accidentally swapped with a FET. After replaced the diode, they and the large diode produced heat.

Not sure what to do now. I guess I will try to Attiny mod one of my untouched HX-1175B1's to see what happens. I'm done a lot of experimenting on the HX-1175b. So maybe I inadvertently changed something without realizing it.

Continuing on from my last post, I tried to use higher resistance resistors. All 1206 sized.

Two R33's (Cumulative .165 ohms):

Got same current readings as above except for the high mode. High mode read 10.x amps for a couple seconds and then the resistors blew.

Four 1R0's (Cumulative .25 ohms):

Got lower current readings in all modes. PWM 100 read almost 2 amps even and High mode read almost 7 amps for a several seconds and then the resistors blew.

Next, I'm going to put this driver aside and try the Attiny swap on a fresh "B1" driver.

Keep up the good work!

ImA4Wheelr, stop and rethink. You are in DD. You have soldered PWM directly to Gate.

IMO there should be no reason for you to go directly to the buck controller with your PWM output from the ATtiny. Figure out which pin on the stock MCU controls the buck controller.

I can stop and rethink all day long, but without some basic electronics knowledge I will get nowhere. I appreciate your help wight, but please understand that I have no formal electronics training. I'm not asking to be spoon fed. Just a key word or idea will get me searching in a particular direction. I just don't have enough knowledge to know which direction to search.

I do realize it tied into the output point from the buck controller (I called it a converter above), but it was the only point that worked that far down stream. I did try to get as far down stream of the gate for a PWM feed point that would respond to connecting directly to the 3 volt "+" feed. I figured I was just sending a pulses to the gate that turn it "on and off" and that the source to the FET was regulated.

I'm going to try to use my osciliscope tonight. I bought from a surplus agency over a year ago but keep getting intimidated by it. I will try find which pin the buck controller is receiving the PWM from. Then after testing, I will pull the MCU and buck controller that take some new trace pictures for the OP.

The scope should have a test point you can use which produces a 1khz square wave or something (marked on the front). Use that to get started. I know almost nothing about scopes and can hardly use my own surplus scope.

The buck controller senses current [by measuring voltage drop over the sense resistor bank] and turns the FET on and off accordingly (and rapidly). At high input voltages the FET will be off a lot of the time (think 50% if input is double output). This is exactly what we want for regulation; other parts of the buck circuit ensure that voltage never goes too high - we don’t need to talk about how but it’s related to the rapid switching of the FET. A PWM input will tell the buck controller to keep the FET off even more in order to give lower-than-maximum modes. Keeping the FET at 100% duty cycle (always on) is direct drive. If it’s not turning on and off rapidly then maximum voltage will be allowed on the output. In a buck circuit the FET should never be at 100% duty cycle. [100% duty cycle is fine on the PWM input of the buck controller though, since this just tells it “don’t turn off any more than you normally would to maintain the current you are supposed to”]

The point of the above is to explain that the buck controller itself is in charge of regulation. If you bypass it that is bad.

I also have no formal electronics training, so you can only wave that flag at me so much ;-). I’m still happy to help.

Let’s get down to business:

  • You never posted a clear pic of what’s under the MCU (traces). That might be helpful or it might not.
  • In post #29 you say ‘clockwise’, but we mean counter-clockwise, correct? (If not post a drawing to help please.)
  • In post #29 what mode is the driver set to?
  • Let’s re-check pad voltages without the MCU installed. Please record them so that we may compare with your results from post #29. This is what I really feel like we need to see right now.
  • If you haven’t gotten a handle on your scope yet, maybe try this: If you have a working stock driver hooked up, please power it up and set it to medium. Do a quick check with your DMM and look for any pins which seem to have a significantly different voltage from the values recorded in post #29. [If the driver was set to medium for your results in post #29 then recheck with the driver set to High this time and look for pins that show a different voltage.]

FYI: In my last suggestion we are not looking for a true/accurate voltage. The DMM will probably show something inaccurate, but hopefully different, for different PWM duty cycles.

OK, looks like we are in business for good this time.

Sorry for the delay. Finally got a chance to get a MCU and buck controller trace shot. Wight, I will have to get back to you on clockwise/counter later. I'm too tired to think straight right now. Actually, the trace picture below should answer what you are seeking. Full power is going to the bottom left Pin in the below pic. The Pin above it is the Ground. The second Pin up on the right side of the MCU appears that it could be for voltage dividing.

As discussed earlier in the thread. PWM is coming out of the top left MCU pin in the above photo. The trace show it going into resister to ground and through another resistor to the bottom left Buck Controller pin. Duty cycle readings with a DMM confirmed the PWM signal at both points.

In the past, I tried to get the driver to turn on feeding power to the top left MCU pad, but nothing happened. I would like to try that again as I wonder if I did something wrong. It seems like it should work.

Anyway, relocated the PWM feed to the lower left Buck Controller pin and am now getting normal current readings at the emitter. With stock resistors current read:

PWM Current

1 Too low to realy measure. Says .01 amps sometimes

3 Same as above

9 Very low. less then .06 most of the time

27 About .28 amps

100 1.9. ish amps

255 Almost 7 amps

Added one R10 and got the following readings:

PWM Current

1 Too low to realy measure. Says .01 amps sometimes

3 Same as above

9 Very low. less then .05

27 About .3 amps

100 2.3 ish amps

255 Starts around 9.7 and drops fast and stabilizes just above 9 amps

Here are a couple pics of the set up.

Check out the size of those stock resistors. That green resistor I added is a 1206 size. For other pictures that may help more clearly see the connection points, see Post 39. Just keep in mind that the wrong pin on the Buck Converter is used in that post.

I only ran the driver for about a minute or so. Since I don't have the beefy brass ring to absorb heat, I didn't want to run too long. Driver was warm to almost hot. Heat seemed to be from the voltage sense resistors and the Large Diode/FET side of the driver. My impression is that the driver will run fine at this current if properly connected to the pill for heat sinking. The large diode is rated for 10 amps per the data sheet.

Something was whining pretty loud at PWM 100. Mounting in a light might mute most or all of it. I'm not really concerned about it. If anyone wants me to try anything to get rid of it, let me know. I can't guarantee I will get a chance to try it, but will if I do.

Here's another trace shot. It's hard to get the traces that are over the cell side positive terminal.

Just wanted to say a big thank you to BLF member wight for taking the time to help me develop a MCU mod for this driver. His (assuming he's a he) guidance not only helped me figure out this mod, but he also noticed a mistake that I made at an earlier time when I swapped out what I thought was 2 FETs, but were actually a FET and a diode. The mistake didn't seem to hurt the MT-G2 and it made the driver run cooler, but it would have most likely been problematic to less hardy diodes like XM-L's.

Thank you wight

Here's at attempt at a consolidate the "Attiny13A piggyback how to" so the whole thread doesn't have to be read. Legend:

A - Pull the HX-1175's MCU

B - Connect PWM feed from the Attiny13A to this pin on the Buck Converter (ignore the red wire. That is not the correct pin).

C - Connect ground for Attiny13A any where around the ground ring

D - Connect power feed to Attiny13A here

I’m glad this thing is working. Now to find a reliable source for these.

And one with an un-sanded buck controller.

I’d still like to see a picture with all pin descriptions. I can’t understand when you do lists or clockwise / counterclockwise.

I consider the source I listed in the OP reliable.

The paragraph above the first picture in Post 50 doesn't have the info you need?

How does this driver behaves on different voltages?
It’s listed as 3-18V but I guess it is buck only like always…

I think I’m starting to see. You say “Full power is going to the bottom left Pin in the below pic.” I read that as “the bottom left pin” - a pin which does not have anything hooked up to it. That’s why I assumed you meant the bottom right. Now I see you meant the pin above the bottom left pin. When you said “full power” I was also confused since I wasn’t sure what you meant by that. Looking back at post #29 I’m sure you meant ~4-5v, not battery voltage. (remember, as far as I know this is a mystery MCU. So I don’t rule out putting battery voltage on it). Anyway I think I’m clear now, thanks.

There are 5 pins hooked up though, so I’m still curious what that final connection is on the bottom right. Looks like it’s not hooked up to anything but a bunch of unpopulated stuff. I still wonder what it was for…


I have only been using the driver with MT-G2 using 2S and 3S cells. Based on the way it behaves, I think it will have no problem with 4S cells. I will try soon to find out. I will also try 1S cell with an XML.


You're absolutely right on all counts. So sorry for the confusion. The second Pin/Pad from the bottom on the left is receiving a little over 3 volts. I'm not sure why the there is a difference between what I measure now at that Pad (without the MCU in place) and what I measured then with the MCU in place.

I will be modding another driver soon. I will take voltage readings again both with the MCU on and off the board and report back more clearly.

Nice job!!!

I wish I had time trying to replace the MCU on LD-29 :frowning:

I think Werner is wishing it was a Boost/Buck driver (or maybe it is? - unlikely :frowning: ).

It’s partly just the way I read things. One possible reason for the different voltages you observed would be “potential”. If you did not use the same ground point with your DMM you could get different readings. I look forward to your measurements with the next one. That should be telling!

Maybe I’ll at least probe one very soon.