Using two drivers in parallel, while both still have functioning MCUs, can cause problems. If you've ever had two identical lights with identical drivers, set them to strobe, and let them run a while, they go out of sync. Like a twin engine boat with the throttles not set right. No way around it, it's caused by just the slight variation between the cheap parts used on the drivers. The real problem is in the lower modes. If your low mode is 15% PWM, it'll be fine when both drivers are on at the same time and off at the same time, but when they get out of sync the light output will cycle around bright and dim and all over the place.
Best to only have one controller for all the boards. All the common small drivers just use one output pin on the MCU to drive the thing that regulates the current (whether that's a 7135 or a SOIC8 FET or a TO-252 FET, they all use a PWM signal to control what the LED is doing), you just have to find which pin it is and add a jumper from the brain board over to the dummy board that's had the MCU removed. With common drivers it's easy, they've been poked and prodded enough that all the pins and traces are well known already. With others it's just a bit of poking around with a DVOM.
The slave/brainless drivers do not need any connection to BAT+, all these drivers only regulate through the negative path, between LED- and ground (and any fancier driver that doesn't work like that shouldn't be used for this anyway). At high currents (and why else would you do this?) running the BAT+ through a driver's PCB can be a restriction; the brain-board only needs a tiny bit of BAT+ to run the MCU, nothing else on the board uses any positive voltage at all. Run the main LED+ wire around the drivers and straight to a big fat connection to the battery, then split off that point with just a small wire to feed the single MCU.
This is, essentially, a master/slave setup just like two 105Cs. Just that 10 of the chips happen to be on a board that's not a 105C. All the pins and traces do the same things. (the red wire from the BAT+ pad to underneath the 105C is only there to feed the MCU, it has nothing to do with the BAT+ to the LED at all)
This is all you need to do if you want the easily programmable attiny with a nice UI to control a totally different driver:
Thanks for the info Comfy. How long does it take for the PWM to get wonky? I have this one sitting here on low right now for about 10 minutes and it’s just a nice steady low. Did I just get lucky with this particular driver? I’ll leave it running and see but so far I can’t notice anything wrong with it at all.
There can also be a spread between the time measured for a half-press, if you always stay inside the window for both drivers when changing modes it'll be fine but if by chance you get too close to the time limit one can change modes while the other one doesn't. The issue with 'potential problems' is that it may work perfectly fine, right up until it doesn't...
Thanks again, I’ll keep this thread updated and post if I have any problems. I messed around with it quite a bit and now I’m giving it goofy half presses and still no problems. Supper fast changing, clicking it on and off rapidly over and over still no problems.
This is the driver I’m using. I jumped one of the three resistors on the bottom. Between the three the registered something like 6.7 before jumping them.
Thanks OL - this takes the guess work out of the wiring. I like the idea of running the battery + directly to the LED(s), so there is no flow through high resistance traces on a driver. Also, the way it looks, the slave 7135's should have better heat dissipation paths than if stacked all on one board because of the additional tracings and wiring of the slave board?
I was also gonna say that it works great with an MT-G2. I've done it in a ZY-T08 and I think that Old-lumens has done it with several of his builds (including the recent Courui MT-G2 mod).
I believe it helps. It sure couldn’t hurt. I have come to the point where I don’t want to stack any more unless absolutely necessary and if I do, then I want a copper wrap to help with the heat.
The drivers are in parallel. The batteries are in parallel series only because I need the voltage thru the chips. Otherwise, as long as the drivers are master slave, the batteries can just be parallel for a 3.xx volt led. The master has the zener mod, to protect the mcu and the 7135 chips do need extra heat sinking. If not, the light gets dim very quickly, due to reduced 7135 output. The last time I tried using .010" thick copper sheet and wrapped the drivers, soldering the copper to the tabs of the chips and it seemed to help a lot.
Do you want to combined the output’s and then run the emitters hooked in parallel or do you want each individual driver to run one emitter independent of the other (but still controlled from only one MCU)?
