rodjer_ramjet

Hey guys just looking for some ideas on the easiest way to make a 24 hour lighting program with about 3 or 4 outputs using PWM dimming for Leds

I would also like to be able to adjust the overall brightness.

was looking at using a 24V switch mode PSU, suggestions appreciated as to how to get an ideal voltage cheaply?
with power through a FET with the signal controlled by the microcontroller or whatever

looking to make this as efficient as possible, also some stats on the leds

Vf 3.4
Led current average from 0 mA to 1000 mA with 50% max duty cycle still sorting out heat sinking so its a rough guess.
number to be controlled X number of banks of 24 - 30 leds pretty much whatever fits with the power supply voltage so I don’t waste power in resistors.

As a reference looking to make something similar to the Solaris led reef lighting system.

Cheers Andrew

rodjer_ramjet

just a question did i give enough information? does this mean there is nothing avaliable to my requirements ? any feedback is much appreciated...

Cheers Andrew

HarveyH42

Just be patient. There are a couple of aquarium lighting threads on this site, so there must be one or two people with some interest. Kind of a unique project, might be easier to find something similar, and ask for help to modify it to suit your needs. I know the search here isn't the easiest to work with, but I think on of those threads is pretty close. I think they were going for a moonlight type effect...

philba

I assume you are talking more about how best to power the LEDs and not how to control them. There are lots of switcher chips designed to power LEDs. These would be the most efficient. Many of them have control inputs that support PWM dimming. The datasheets will give you lots of details. for example, check out this one from linear http://www.linear.com/pc/productDeta...4,C1768,P13452 It handles a wide range of input voltage, can drive up to 4 LEDs and supports PWM control. I'm not pushing this specific chip, it's just an example of what you can find. National, Linear, Maxim and others have numerous choices.

edit: I just realized you wanted a lot of LEDs - look at this one http://www.linear.com/pc/productDeta...4,C1769,P37747


On the actual control, this is pretty straight forward. you have a time of day clock, a calendar function (driven from the clock), a computation of SR and SS based on the calendar (and location), computation of the desired brightness and then use that to set the PWM level. Your brightness level would basically be a divider of the PWM level. all that stuff is discussed ad nauseum on the internet - google is your friend.

rodjer_ramjet

Thank you for the info so far that chip by linear looks good and the time of day clock and calender function was the part I didnt know about makes it a lot easyer thanks.

x947

rodjer -

sent you a pm . . .

I want to do the same thing. the dimming does not have to be "smooth" but can be "stepped" up and down. 100% for an hour then 80% for an hour. then up the power - 0% then 20% for an hour, 40% for an hour etc.

can a digital "on - off" timer be modified to accomplish this stepping ??

Mike

x947

oh, BTW, where could I get something like this made . . . I am electronics ignorant, can't solder, and am an accountant by trade !

HarveyH42

Note the date int the upper left of the post. Sept. 2007, the OP never returned to it.

x947

thanks harvey . . .

I was aware of the date . . .

HarveyH42

Sorry, I just remembered this topic had come up a couple of times, thought it might be old, I don't always look at the date. We've had 2-3 year old threads resurrected by new users. Just hoped to spare you some grief, if waiting for a reply.