Electronics questions

[HeyGuysWatchThis]

First of all, I'm not an Electronics Engineer by any means, so sorry for the dumb questions, but I want to make sure I make a good plan and make something that will do what I'm hoping without letting any smoke out

Anyway, I have a Life+Gear 2C flashlight that I want to get set up for running on 1x18650. The flashlight has a Cree XR-E emitter. I would like to put in a driver to get a regulated L/M/H interface. Hidden disco modes might be fun as long as they are not too easy to accidentally activate.

The 18650 cells I have are recovered from laptop packs, so they are unprotected, of course, so I would also like to incorporate some form of over discharge protection. I am thinking to make 2 removable modules that would go in the existing battery compartment so that the mods would be easily reversible so I could go back to 2C configuration in a pinch. One module would basically be just a sleeve that centers the cell in the light, while the other would be the electronics module, including the regulation/modes driver and the protection circuit.

I have looked around at Kaidomain a little, but I find the site poorly organized (which I could live with), and very slim on specifics of what the circuits do. I would love to draw on the experience of some of you folks here who have done this stuff before and can point me in the right direction. I'm pretty flexible on all these ideas if someone tells me it won't work, or have better suggestions. Pretty much the only thing I'm unwilling to change is the regulated modes and the single 18650 configuration.

 

[HeyGuysWatchThis]

Also, will I need to worry about dissipating heat from the electronics I am looking at adding?

 

[Al Combs]

Here is a good driver for an XR-E and 1*18650 that doesn't require mounting to a heatsink. Mode 2 keeps the disco modes hidden.:laughing: Here is a good driver board thread if you want to look at what's available. The type you need is a buck regulator. I'm assuming you're aware of the inherent danger of using unprotected batteries. If not, do a forum search for "lithium explosion". That said, you definitely don't want a buck/boost regulator. Normally that would be the ideal type regulator for use with a single protected Li-Ion.

You still have no short circuit protection, but an AMC7135 regulator is effectively direct drive at ≈ 0.2 volts above the Vf of your LED, As battery voltage drops below about 3.8 volts, the light gradually gets dimmer. Before it becomes a serious charging hazard, the only way you'll be able to tell the light is still on is if you look directly at the LED. You'll know when it's time to charge the batteries. Speaking of which, 2C alkaline batteries might be a little too dim to be useful with this type of regulator. If they were NiMH, it wouldn't work at all. The chip threshold is 2.7 volts.

 

[HeyGuysWatchThis]

@Al Combs: Yeah, I had found that driver after my original post, too. Have you actually used this driver? Was it reliable and effective? To restate my second post, will it develop a lot of heat I will need to dissipate? As far as short circuit protection, couldn't I just put a one-way diode in between the battery and the driver board?

As far as the Alkaline/NiMh issue, I would only be using this driver with the Li-Ions. When I said that I wanted to be able to go back to 2C configuration, that would include removing this driver, because the driver would be going into the extra ~1.25 inches between the size of the 18650 and the 2 C cells.

For the protection circuit, I would charge the battery once it dropped out of regulation, and to protect against overcharging, I will be using a quality hobby charger (yet to be selected).

Also, will I get more output from the light with this driver on high than with the original 2C direct drive configuration?

 

[irv_usc]

I've really started liking the shiningbeam drivers since getting a light with one...

http://www.shiningbeam.com/servlet/the-133/**NEW**-3-dsh-Mode-Regulated-Circuit/Detail

no strobe/SOS though.

 

[Lynx_Arc]

let me get this straight, you want to put a driver before the 2C boost driver in this light? This would reduce efficiency an could actually overdrive the boost circuit if it was getting full output from the first driver then outputting that into the 2C boost circuit if that circuit didn't go into direct drive it is possible you could either blow the emitter or the 2C original driver by overheating it.

 

[HeyGuysWatchThis]

let me get this straight, you want to put a driver before the 2C boost driver in this light? This would reduce efficiency an could actually overdrive the boost circuit if it was getting full output from the first driver then outputting that into the 2C boost circuit if that circuit didn't go into direct drive it is possible you could either blow the emitter or the 2C original driver by overheating it.

Hmm, I had the impression it was simpy direct drive. Like I said, I'm no EE...

 

[Lynx_Arc]

Hmm, I had the impression it was simpy direct drive. Like I said, I'm no EE...

nope... a 2C LED light would have a boost circuit as even brand new cells don't put out enough voltage to properly drive an LED near Vf.

 

[HeyGuysWatchThis]

nope... a 2C LED light would have a boost circuit as even brand new cells don't put out enough voltage to properly drive an LED near Vf.

Then would I be likely to wreck it by just putting in the 18650 without any other electronics?

 

[Lynx_Arc]

Then would I be likely to wreck it by just putting in the 18650 without any other electronics?

not knowing what boost circuit design in it, I would say it is very possible to fry something. If you could crack open the head and post pictures or find a thread related to the light someone who knows components better than I do could possibly tell you if the circuit would handle the higher power level of the lithium ion. I would recommend instead you try to find a buck/boost driver and just take out the driver in it. That way you can use either option. If you are going to go to all that effort you may even consider upgrading the LED too.