My very first mod, I could use some help/driver advice

Hello guys,
as said, this will be my first attempt in modding, I tried to read up on what to do/use best but the more I read the more confused I got....:thinking:

I ll explain what I want to achieve so you can maybe give me some help.

I am working railroad security at the moment and I need a light ,mainly for signaling, which is able to put out white and (in emergency) red at nearly same level. (just additional low-powered red is not sufficient). Initially I was thinking nitecore chameleon - but sadly its against regulation. We are allowed only white and red, any light that can also put out green is forbidden - even if its somewhat hidden in the UI. Only train drivers are allowed the additional green. Stupid, but thats the way it is.

White is used for signaling among the coworkers at night and red is used only in an emergency to stop a train. But if I ever need the red - I need it FAST without fumbling or having to switch through modes , etc. So the old case whith the sliding filter is not so bad.

To keep matters simple I decided to use this old metal flashlight as a project box. I can rip out the original guts and I will also have to remove the green filter -but thats not a problem. I had it sitting around and since there is a good chance it will be dropped sometime on railroad gravel I prefer to keep it inexpensive. Yes ugly, ugly , i know - but it has enough room to even keep 3 additional spare batteries if I make a small enough battery holder, which is something I like.







What I need is :

-needs to run on 3 AA alkaline (we are given these free) or maybe 4 eneloop (private purchase)?. No li-Ion rechargables.

- I dont need it to be ultra-bright, 300-350 lm at max is more than enough for me.

- momentary is an absolute MUST HAVE, its main use is signaling.

- I dont really care if its more flood than throw, Ill try to use the original reflector if possible, compared to what we are issued with a XM-l U3 will be generations apart in brightness...



For LED I was looking at a Cree XM-L U3 on a copperboard. This will be mounted on a fairly flat but large (1"x 1") copper heatsink fixed to the case. The driver will be placed somewhere else sideways in the case- its enough room there.(I am somewhat limited in terms of depth behind the reflector)

https://www.led-tech.de/de/High-Pow...U3-auf-Kupferkernplatine-LT-1943_120_170.html .


I intend to run it only on the nominal 700mA (=320lm) - which is more than enough in terms of brightness for me.


Where I am at loss is what type of driver I can use? I could (grudgingly) live with a simple 1 mode 2x7135 linear driver but It would be so much nicer to have 3 modes like: low-med-max. I dont really want much more than that, no blinky, strobe, SOS etc just 3-mode ,keeping things simple and non confusing. I also read that these linear 7135 drivers are not the most efficient, - but well, I really dont know so much about the subject.

Please keep in mind I need this mainly for signalling so momentary is a must and a driver that cycles through all modes every time I press the switch is useless for me. Adding a momentary switch in addition to the "main" switch would be possible (how is the wiring done?)- but if its not needed I d like to go without.

So what are my options in terms of drivers? I was searching the net but most of what I found was xx-mode, high powered ,2-3A drivers, not the simple thing I looked for.

My soldering skills are mediocre at best, I am able to solder wires to the star and to the driver for connection and make a heatsink from copper stock, but modifying an existing driver by adding/removing parts or flashing a custom UI is above my skill level.

If the driver is sold with clear instructions on where to connect what ( momentary switches, LED etc) or if such info on it is avaliable somewhere here from other builds it would be a definite plus for me - I cant really read circuits...


Thats about it, sorry for the lengthy explanation and any help is appreciated.
I am open to suggestions, but keep in mind I am a newbie at cobbling a functional flashlight together so the less cryptic your remarks are fore someone with less knowledge than your own- the better I can make use of them. I really tried to read up on all that stuff by myself but its just too much to take in at once. :shrug: So I finally decided to ask for help from experienced members...


If I were more advanced I would aim for separate red and white LEDs in the case but since this is my first , I need to use 3AA and the ugly old case with the red filter is at hand I like to keep it simple.

Regards
Ralph

sounds like a fun project.
I've converted a couple of incandescent bicycle lights over to LED, so I can appreciate some aspects of the challenges.

For a driver, my tendency has been to just use a simple linear current regulator. The losses are really not bad when you consider the average cell voltage of 1.25v or so... with a 3.0V LED, you get 80% efficiency. It's more efficient as the battery voltage drops, and less efficient with a 1.5V battery.

For heatsinking, some sort of external heatsink should be used. A few square inches of surface area ought to about right.

Is the case acting as part of the circuit? It looks metal, and it's not clear how the batteries are connected to the bulb and switch. If the case does carry current, be careful when creating the heatsink so it doesn't end up creating an unintentional electrical connection.

Good luck and have fun!

Welcome to the forum!

I think you've picked a good project for a starter.

To get closest to the original beam pattern, you'd want a light source the same size and location as the original bulb's filament, or pretty close to it. That means you'd probably want an LED with a smaller die. I haven't followed the latest explosion of LEDs from Cree, but the XP-G2 would be smaller, and the XP-E would be smaller still, and able to handle the 700 mA you mentioned. They'd also be cheaper.

I've not seen a driver available that has multiple inputs (except one I make, which would work but is massively overkill). I think if you want to be able to message by pressing the button, you're going to be stuck with a single intensity. Unless maybe some of the programmable UI's could be made to require a long press to change intensity (longer than than any message pulse).

You could, however use two or more 7135 drivers to select intensity with one switch, and control all of them with another switch for signalling. I think that's probably your best bet. We can definitely help you figure out how to wire that.

With a linear driver (like the 7135) and three cells, either alkaline or nickel, you'll suffer substantial dimming before the batteries are depleted, and you'll probably want to change them out well before then. Four nickel cells is, IMHO, perfect for optimizing efficiency and achieving long run times at full output. Four alkalines is not bad either, but you won't get the runtimes you would with nickel. Then again, maybe you don't care.

With four cells you should pay a little attention to heatsinking the driver. With three cells, no worries.