XM-L driver options with dimming? custom board maker?

[pinned88]

Hello! I have my first custom project light I'm working on, and I'm trying to wrap my head around the different driving options. Be warned, I am still scratching my head a lot and trying to figure out how all this works. I have a lot of ideas floating around in my head for how I'd like this to function as it is a specialty light... The primary question I have is if there is a company I can call and have a custom driver board built?


If you want the background, I have a setup where I will need a small footprint driver for the XM-L, 3a would be ideal since I can use all the light I can get. the input voltage will be 7.4-9 volts, and if it could accept 12 that would be better. I'd like to have the ability to dim the light and conserve battey life while doing so, am I on the right track thinking a CV/CC with PWM would be the best option?

The biggest problem I have is the design of the light is such that I dont have much room for the driver board where the LED will go... about 3/4" diameter and up to 1/4" in height. I do have additional room in the body of the light and I'm trying to figure out if it would be possible to mount a basic CV/CC driver in the front of the light, and a PWM circuit seperate in the body? meaning the PWM circuit would come before the driver itself and allow me to have my dimming/battery conservation and split up the electronics to save space near the head of the light. For what I'm using the light for I only really need 3 levels... High, Medium and Low.. I have an idea for the body that uses 3 fixed resistors in place of the potentiometer in a standard 555 PWM circuit so that you can change the brightness by means of changing which resistor is fed with power.

Is this possible? I have a guy I can pay some $$ to have him build me a custom board if need be, though he is not much of an LED guy so I'd still have to pay someone to construct a diagram and spec parts. But if it meets my goals, I'm not opposed to that. I'm trying to build a better caving light, and light in the cave is one place I dont want to cut corners! :candle:

 

[hellokitty[hk]]

am I on the right track thinking a CV/CC with PWM would be the best option?

I think all three of those were contradictory.

 

[1215]

I think all three of those were contradictory.

AC led drivers that are PWM dimmable are usually CC/CV capable depending on how you load them.

 

[pinned88]

I think all three of those were contradictory.

I see what you mean... my mistake. If I understand correctly, CV/CC circuits operate much like a PWM circuit, pulsing on and off to hold either a constant current or voltage. what I'm trying to figure out is if it is possible to use a PWM-like circuit to dim a CV driver, or wire a CV driver in a way where you could mount the "dimming" portion of the circuit in a remote section of the light.

 

[hellokitty[hk]]

AFAIK:
CC constant current means the driver will vary the voltage to hold a constant current. There is no pulsing hence the constant. Though you may be able to add an external PWM circuit for whatever reason.

CV constant voltage means the driver will hold a constant voltage even through varying load (and current). There is also no pulsing here hence the constant. Again you may also be able to add an external PWM signal.

Inside the actual driver there may very well be some sort of PWM going on as in a switch-mode power supply, but the output should be smoothed out so that it is a constant voltage output or a constant current output.

And I think it's either CV or CC but not both at the same time, that wouldn't really make sense.

Whether you can use PWM to dim is dependent on the specific driver and you'll just have to check that up situationally. For CC drivers it may also be possible to replace a sense resistor with a logarithmic potentiometer of the proper range and that IMO is a better way to dim.

I think there are several very cheap drivers on DX, intl-outdoor and KD that meet your needs...

 

[Danjal]

I think there are several very cheap drivers on DX, intl-outdoor and KD that meet your needs...

Could I get the websites for those? Tried a google search. Found intl-outdoors.com if thats correct. What are the others?

 

[hellokitty[hk]]

Dealextreme has some I am sure.
The common Kaidomain driver used is KD Super Output SSC P7 LED Driver Board but I also noticed this one that looks like it would also work, but I have not heard anything about it 6-15V, 3A Circuit Driver for Bike Light

 

[MikeAusC]

To drive LEDs with constant brightness you need constant current - CC/CV is used to charge LiIon or Lead Acid batteries. If you set the CV higher than the highest LED voltage, then it just acts as CC driver. LED voltage will vary with temperature and current.

To dim the LED you can either reduce the current - or pulse the controlled current on/off = PWM.

 

[Justin Case]

How about a Shark Buck 3A with an external pot to control brightness. For something like caving, I personally would not trust my life to a DX or KD 3A driver.