My first adventures with the transistor circuit, quick story because I need sleep now.
I used one of the older boards, cut some traces, scratched off some solder mask and got the circuit done.
Long story short, it does not work straight out of the box, I tried lots of other configurations and resistor values (the bleeder eats voltage so that has its influence on the working of the circuit), even refreshed my knowledge of NPN transistors for this (keep enough voltage over the base), I get red light (most of the times), I get blue light, but no switch-over at certain voltages. Too low resistor values even keep the driver MCU alive (LVP warning ), etc. What does not help is that I have no electronics background.
A dedicated board would help the testing, but if it will work at all in the end, I don't know.
An explanation of how I think the circuit works: at voltages closer to full battery the green led (I used blue btw) lights up and that keeps enough voltage on (and thus current through) the transistor base that a free current flows from emitter to collector, thus bypassing the red led, that stays off. Below a certain voltage the green led drops out, the voltage between the transistor base and ground drops below 0.7V, the transistor stops conducting and the red led lights up. Anyone knows better than this??
I disagree. I feel adjusting such a small pot with such a wide range of resistance is going to be very very touchy. And you won’t be able to see the led’s when you’re adjusting it. I’d rather have preset options that I’ve already dialed in to where I want them.
That’s just my opinion, but it sounds like the boards pyro already made are perfect for your desires.
you can also dial in your preference and mark it with a permanent marker so you could simply “switch” between preferences once you have found them. Depending on the position it might be able to write down some “clock like labels” so you can just use resistance number 3 and 8.
Also I would simply wire it up while adjusting it, crocodile clips are our friends;)
But maybe I am underestimating how close high and low brightness are…
The benefit would be that no parts would be in the battery compartment. And that the hole could be not in the center where the spring with bypass is a big obstacle.
But anyway it seems that the rear adjustement trimmers are rare and big…
Just an FYI. Looking at a mini omten there is a five pin locator on the bottom. Four .55 mm plastic pins in a 2.7mm square(2.9-3.1mm outside dimensions) with one in the enter. Could be easily cut off or pattern incorporated into boards.
The switch I looked at says omten and came off a switch pcb with matching holes. I figured that your holes were for your switch. I have some small push button switches with the same pins.
Okay, I’m running into some issues. This is the V3 20mm board.
I assembled it like the previous versions, but the LED’s won’t light. I did some checking with the multimeter, and things do appear to be getting power like they should.
The spring wire is attached to that central via.
I did cut off the switch, and found a possible short from the NEG side to that POS via trace. I shortened the leg of the next switch, but the results are the same: no joy.
Here are both sides, see anything obviously wrong?
I think that’s the short he alluded to but yeah, that one for starters. Have you checked the polarity of the LEDs and verified their operation with a low cell? A pair of half drained alky’s or nimh’s would be better.
i was just modding a prototype tail cap Manker sent me for the new X6/X5 lights. They came with two 2ohm resistors, one for each LED (red). Removing one of the resistors made it better (less bright) but I still found it to be too bright so I changed it to a single 3.9ohm resistor and it wouldn't even light up at all. I swapped in a single 2.5ohm resistor and it is about perfect.
i love the idea of a pot being built in but wanted you to know that anything over 3-4 ohms is pointless. The workable range is only about as high as 3ohms in my findings so using anything too wide in range will be nearly impossible to dial in to even get it to light if you use a 50k or higher like I read some of you wanting to do. Try to use a pot with as low a range as possible.
If anyone has had a different experience than I did I'd love to hear about it. :)
), etc. What does not help is that I have no electronics background.
