I’ve been reading pretty much on the forum but now I am starting my first DIY I have a few questions.
I’ve only been into flashlights for about 2 years, it started with a EagleTac P20A2 and a PN20A for my keychain.
Later I bought a 3 led SKYRAY king (clone maybe?) which I’ve now modded with a self designed driver and a LED ring switch.
I also have a Thrunite Archer 1C which I really like as EDC light when I need a little more light or an easier to hold light then the PN20A.
I’ll also ask my questions somewhere else, but if anyone has any answers I might as well post them here too =)
The threads on the head of the SRK are wearing out (I unscrew the head slightly when not in use). Is there any way to fix this?
If the threads are not fixable (which I whink is the case) I’d like to convert it to using 3x XHP50. I’ll design 2 contact plates so the batteries can be placed in 2S2P config.
The head can then be screwed in and glued(or otherwise fixed) to the body, battery replacement will happen from the rear then.
A few things are not completely clear for me here, when using a driver with 2S it seems I need a zener mod. I know why this is needed but I do not know how exactly this is performed.
Do I just stick a zener diode on the GND and VDD pads of the uC?
I want to make a 2S light using a XHP70. is a Convoy C8 with an extension tube a good host for this?
Same question with the driver here, but with 1 answer I’ll probably figure it out myself:)
For the zener mod on a standard Nanjg 105c/Qlite etc you need to follow the instructions here https://budgetlightforum.com/t/-/20724
However if you go for a driver based on one of the OSHPark boards designed by BLF members, then there are usually pads provided and labelled for Zener modding. Depends on the driver.
Yep, just watch for correct polarity of the zener diode on the cap. The stripe should be on the non-ground side of the cap, facing into the driver on the Nanjg105c.
Oh and just in case you wanted to go crazy and add over 35 7135 chips, you’d need to use a 100Ohm resistor instead of the 200.
Just to supply enough current to the MCU to drive all the 7135s.
FET is what we call direct drive, so more or less like directly connecting the LED to the batteries.
Pros:
It’s going to be as bright as the batteries will allow, if you want max amps no need to stack tens of 7135 chips to achieve it.
Still has configurable lower modes and plenty fast PWM.
Cons:
No constant current regulation, as a result batteries drain very fast and output drops off accordingly. Suitable only for “HotRod” type lights.
Potential PWM whine at lower modes
Puts a lot of strain on batteries so requires high drain capable cells.
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7135
Pros:
Regulated constant current based on number of chips. They will maintain this output current as long as VBatt remains higher than Vf of the LED.
As a result you get longer stable runtime at a constant (lower than DD) output level.
Relatively easy to set max output current by stacking/removing extra chips.
Capable of higher PWM frequency than fet, so no audible whine at all.
Cons:
If you want maximum output, it requires many 7135s and stacking them all can become a pain. Not to mention they take up a lot of space.
Ultimately I think the smart choice at the moment for anything above like 4amps per XML2 led is to go with a fet driver.
Higher Vf of current XML2 leds has led to shorter and shorter regulation phases on high current 7135 drivers. Then you have the hassle of stacking all those chips for no real benefit.
It used to be the case that a DD fet driver would drive a first generation XM-L to 8-9Amps easy and if you wanted something in a more sensible 5-6A range then a 7135 based driver was still a smart choice. Now with the new generation of LEDs they seem to struggle to get above 5Amps direct drive so it’s a bit of a different ballgame.
The driver can be found here: https://oshpark.com/shared_projects/nOmCqmpP
It is using a MSP430G2231 (if i remember correctly) and 18 7135's.
I was planning to use the led around the switch for voltage warnings and stuff but did not get around programming this.
The next driver will use an attiny13 and finished software(except the mode levels ofcourse)
