I tried to guess cell voltage under load and Vf of the emitter to get a rough idea of efficiency. Does it make sense for the driver to be more efficient on High mode?
Again, good info - thanks. It sounds like the included software with a DDS-120 doesn’t allow you to manually change that, but if you make a small time/division it will increase the sample rate on it’s own. This is the thread that leads me to believe that. It should be easy to tell since it displays the samplerate on the screen? There may be alternative software which would allow you to force a higher samplerate, but just making a smaller amount of time/div would do what we want here. Based on the specs I assume that the actual limit is either 50MSa/sec or 200MSa/sec.
EDIT: I could be wrong, but I think that in HKJ’s driver reviews he uses 1μs - 2μs per division.
I’m not sure, but I see that you did not adjust cell voltage sag for the different loads. Considering that we’re talking about 5A vs 2.5A, I’d say you’ve got to do that.
I’m not sure, but I see that you did not adjust cell voltage sag for the different loads. Considering that we’re talking about 5A vs 2.5A, I’d say you’ve got to do that.
Good point. I need to find a HKJ chart for the KK and adjust. I will do that later. What I really should do is set up a driver testing rig so that I can collect all the relevant info needed for this type of stuff.
Right now I only have two Efest IMR18500 handy. This is all jury rigged with different wires, alligator clips and magnets, but I got a reading of 5.9A.
Okay wight, I tested the voltage across the resistors while running the MTG at 13.45A and got a reading of .049v. I tested each resistor, and got that reading. What it means, I don’t have any clue. Hope I did it correctly.
Ouch! I went to take another reading before I disassembled everything, and smoke was coming out of both resistors. I sure am glad I checked this driver before it went into a light.
I looked it all over with a jewelers loop and didn’t see anything different from the other ones. No burned or charred spots. I even tested a few solder spots with my DMM. Then again, my eyes aren’t that good.
Thanks for testing this. You definitely got .049 and not 0.49? 13A across a total of 0.034 ohms should give about that much drop (1/2 volt). Sounds a lot like you are getting DD or as close as this driver will come (with the FET and inductor in the mix).
Could be I suppose. With QX5241 that just gives you a dead driver, but the pinout for QX9920 is different enough that it might give you DD; I’m not sure.
I think that it could also simply be a defective controller chip.
Seems like something is going on with the buck converter. Your driver is acting like mine did when I tied the PWM from an Attiny13a to the output pin of the buck converter. Wight pointed out to me then that I had basically turned the driver into a DD.
Later, I accidentally tore a leg off of that buck converter. I purchased a replacement that wight suggested may work. I will hopefully swap it tomorrow night. I'll let you know how it goes. The buck converters are fairly cheap.
EDIT: My chips were labled LEDA 1402. There was no indicator mark I could find for Pin 1. One of the short sides had a slight nub. I oriented the chip with the nub facing away from the inductor coil.
I added a couple R20 resistors to the above driver (using QX9920 buck converter). Pulls 9.65 amps with both 3S and 4S King Kong cells driving an MT-G2. Piggy backed an Attiny13a with JonnyC's STAR momentary modified by Tom E to include strobe. Wow, what a fun driver. I know exactly what light it's going in. Actually, I know 4 other lights that will be getting the similar setups.
EDIT: I just realized. I heard no PWM whine last night. The only things I did different was the FW just mentioned above and I completely air wired the MCU. In the past, I soldered the PWM leg of the MCU directly to the buck converter. Here is a pic (sorry, it's a bit blurry.)