CCFL PWM solar design

[OrezzerO]

I have recently installed a solar panel, charge controller, and small battery in a cabin on Mt Magazine, AR and need help with the lighting.

In looking for a low volt/draw lighting solution I have purchased and tested a variety of LEDs, flourscents, and most recently a dual CCFL tube made for pimping computer cases found here:
http://www.j-right.com/html/ccfl_pc_stand.htm

The small CCFL tubes put out a really nice 360 degree light for the main room but I would like to be able to dim them to save power and produce a sleeping night-night environment using a PWM circuit behind a wall plate switch.

Does anyone know of either a 12V CCFL inverter that is dimmable or has reference to a dimmable circuit that can be built to drive CCFL tubes?

 

[DonShock]

I don't think you'll be able to dim a CCFL. Fluorescents need a high voltage for excitation. And although PWM supplies the full 12V switched on and off very quickly to the CCFL driver, that would just reduce the input to the driver. The driver itself will still try to maintain full power to the CCFL until it can't. I have a PWM controller for my computer fans. As an experiment, I tried hooking the fan output to a CCFL instead and there was no noticable dimming, it just stopped working.

Also, I don't think I've ever seen a dimmed fluorescent of any type. I'm guessing here, but I do know fluorescents have a fairly slow start as you first apply the high voltage from the ballast which excites the mercury vapor to produce light. It may be that the fairly quick on/off cycle of the PWM that gives the appearance of dimming would not have an ON cycle that was long enough to allow this slow startup process to get to the point of actually producing light.

If you really want a dimmable, efficient, 360 degree light source I would suggest you go with LEDs. Even a single 3W LED will light up a room nicely from just the bare LED with no reflector. And there are several dimmable drivers available and the LEDs will dim using PWM very well. You can go down to the point of a barely visible glow from the LED phosphor. And if you need more light, you can always use more LEDs.

 

[Norm]

Have you thought of using just one 5mm LED as a night light? with night adapted eyes one LED running about 20mA's maybe less will light up a good sized area. Much easier than any other solution I can think of. Just noticed Don in the previous post mentioned a 3 watt LED that will definitely give you heaps of light. I'd try the 5mm LED first.
Norm

 

[orionlion82]

Look here:

http://www.candlepowerforums.com/vb/showthread.php?p=1796498
-its the fixed lighting index.

allso not to be missed is the wacky wonderful world of McGizmo.
http://www.candlepowerforums.com/vb/showthread.php?t=144973


ive got a 2 tube CCFL setup exactly like that in the trunk of my focus.
it aint worth beans in the winter from the cold, but its "workshop bright" when the weather is nice. vast improvement over the 10W incan bulb.
you can actually see what youre getting into now...

 

[wwglen]

1-2 mA with a single white LED does a good job as a night light.

I have a 4-D lantern (cheap incand) that I modded a PR base to take a SMJLED.

I current limited it to about 70mA using a inline resistor in the base of the PR bulb.

I then bypassed the switch with a 2K (I think) resistor whilc allows about 2mA to run through it when the light is turned off.

This will run for a YEAR continiousally with 4 alkline "D" cells and still put out enough to see with dark adapted eyes. Of course after a year it really brightened up with a new set of batteries.

I REALLY need to get around to making a few more of these.

wwglen.

 

[misinformation]

You can definitely dim CCFLs, but you need a special dimmer switch to do it. Normal wall dimmers will destroy them. I'm not sure how readily available they are or how expensive, but we've been working on a bunch of different dimmers for a while now, and they all have ranges of about 100%-15% I believe.

 

[orionlion82]

You can definitely dim CCFLs, but you need a special dimmer switch to do it. Normal wall dimmers will destroy them. I'm not sure how readily available they are or how expensive, but we've been working on a bunch of different dimmers for a while now, and they all have ranges of about 100%-15% I believe.

on a 12V circuit?