Hi all
i have modded a Nanjg 105c with a zener mod like we do for the MT-G2 and i have tried it with 1 cell to drive a XM-L2 but it is giving very low current and when i tried it with two cells and 2 xm-l2 in series it worked great
problem is i want this driver to be able to take high voltage but to run only one XM-L2
It might work if you heat sink the 7135’s really well. You will loose a lot of efficiency because the 7135’s will have to “burn off” the excess voltage. I think the 7135’s may fry fairly fast though.
Yes you can, but not for long time. AMC7135s are rated up to 7V difference Between input voltage and output. At 8.4V with XM-L2s Vf of 3.4v at 3 amps AMCs must dissipate more then 4V if you include voltage drop under load. Without serious heatsinking driver will not be happy. But why would you drive xm-l2 with zener modded driver anyways… Nanjg 105C is only 3$ or so.
I’m guessing he’s wanting to use a 2s host.
Is there a way to do it with a FET driver (BLF17DD V2?). Run 8.4v in but buck it down to 3v out?
What i am doing is this
I have modded 3C mag to triple XM-L2 setup with this method
1st i have tried normal Nanjg 105C but at low i found the Driver is taking about 6.5 volts after about some days of use the driver fried and giving only very low current well i tried another driver same thing happened
so i decided to try zener mod to protect the driver from the high voltage when using it at the low mod
well i did the mod and gave it a try it worked but the leds is running at very low current so i tried to test the driver with the following
1:- 1 LED and 1 cell = very low current
2:- 2 XM-L2 leds in series and 2 cells in series = the normal output of the driver 2.8
now i am stuck i don’t know what to try next
any ideas ?
When driving 3s1p emitters 3s1p Li-Ions and the configuration in the picture you posted the “zener mod” is not appropriate.
The driver does not need to be modified when wired the way the picture shows. That wiring style is much older than the zener mod and it does work fine.
Stop trying to use the zener mod in an inappropriate way and you will not have a problem.
A stock 105c will drive a single XM-L2 at full brightness using a single (4.2v) 18650.
the problem with A stock 105c it is geting fried when used at low mod because the driver is getting almost 7 volts and i am not using it at low on purpose but you have to cycle to get the next mod you want, you know what if i just can remove the low mod there will not be any problem
Please show me your math or measurements.
Nevermind, that checks out. IIRC that wiring was for drivers without an MCU.
Do the Zener mod, but fix your wiring. All three emitters should be in series between LED- and +. If you use the “download” style wiring from your pic I’m not sure what the effect will be. The voltage might not be high enough for correct Zener operation when using the stock Zener mod resistor.
How does that sound?
explain can you please draw it ?
This is the correct wiring for the following setup:
EDIT: fixed picture to correct for an editing oversight on my part. Polarity was wrong on two LEDs.
are you sure connecting a zener modded Nanjg 105c to a 3 cells in series will not fry it right away ?
Yea that’s fine, the Zener doesn’t care if its its got 8.4v input or 12.6, it’ll still only allow 4.3v to to MCU
So you just want higher voltage on an XM-L2? Why? For higher amperage to the XM-L2?
At 2.8 amps the Xm-L2 only needs about 3.4 volts, to work.
If you just want to use more than one cell for some other reason, then why not just use a Buck driver. They would be made for higher voltage.
Am I wrong here guys?
It’s a bit confusing whether it’s one or three LEDs and/or 3 cells in series. Wouldn’t you use a higher value resistor for the Zener mod with 3 cells instead of 2?
OL, his thread is really confusing. It all comes back to troubleshooting he was trying to do for a triple setup. As far as I can tell he doesn’t actually have a need to run 1 emitter on 2s. He Zener-modded the driver and then tried to test it with 1 emitter and 1s.
gamezawy - Cereal_killer is correct.
RBD - at some point there will be a problem w/ too much power across the Zener unless resistor value is increased. I just assumed we are still ok, did not do the math though.
Leaving the same resistor value definitely increases current when voltage is increased.
Right but the 7135’s MAX voltage is 6vdc, even stacked I’m sure you can fudge it by a volt or two…but that is pushing it
remember to regulate they get hot…the larger the voltage difference between Vin and Vout the more power they consume/dump/block (aka heat up)
* No external component required.
* 350mA constant sink current.
* Output short / open circuit protection.
* Low dropout voltage.
* Low quiescent current
* Build-in thermal protection
* Supply voltage range 2.7V ~ 6V
* 2KV HBM ESD protection
* Advanced Bi-CMOS process.
* SOT-89 and TO-252 package
”
AMC7135 spec sheet pdf”:Dropbox - File Deleted - Simplify your life
It’s the excess voltage that’s the issue which is why userdownloads method worked. What’s often missed is the part where it describes how much trace area is needed to dissipate the excess wattage. It mentions up to 1000 square millimeters*per chip* and you’re not going to find that on any nanjg board.