Calling all DIY LED "Junkies" - Your opinions wanted!

[theblondskeleton]

Originally Posted by O2surplus

I think there may be misunderstanding with regards to how the "Analog Dimming" works with this driver. The CAT4101 IC normally uses a "Sense resistor" ( labeled RSense in the chips spec) to set it's upper current limit. The Chip can output up to 1000ma maximum, and that is set by installing a 549ohm resistor between the "RSense" pin and ground. This is how the driver is normally set up. If one wished to run the chip at 700ma instead of 1000ma, they'd have to install a 768ohm resistor instead of the 549ohm unit. I found this method of setting the current very cumbersome, so I installed a 10k trimmer pot inline with a 549 ohm resistor. This makes the output current fully adjustable ( 50 - 1000ma ) and there's no further need to desolder/solder resistors to change the output current. With 6 CAT4101's on board, this driver will be able to handle up to 150 watts worth of leds, that's 6 - 8 3W leds per channel or 36 -48 3W leds per driver board. The beautiful part of this driver is, once the maximum current per channel is set, (using the Analog current Pots) Each of the six channels can be programmed to dim via PWM signals provided by the on board Arduino microcontroller.
I put in the order for the PCB's and they're already in production,so I should have them in my hands in a week or so. I'm going to build 3 of them for my own use and then maybe pass out a few to people with coding experience, that will hopefully be able to show us all - How to take full advantage of this design. I'm a total NOOB with coding so I could use the additional help. ( This is code speak- for getting "SINK" to chime in )

Whoops haha... Well, I never claimed to be an expert. That makes sense, though. So it can operate as a kind of 'driverless' controller? And the current for each channel is adjustable similar to a MeanWell driver? Up to 48 LEDs?

If i understand this correctly now, that makes this capable of doing all the work (driving, dimming, and controlling) for just about any size build, providing there is no minimum quantity of LEDs per channel? Wicked cool! This could save DIY'ers a ton of cash on separate drivers and controllers.

[O2surplus]

Originally Posted by Pickled_Herring

O2 have you posted the Eagles anywhere yet?

I'll post the build files after I've built a few of these and see how they behave in the "real world" I don't want to release the design until it's proven. I tend to design, build, test and re-design a few times over until I'm comfortable enough to post the files for the "Final product".

[O2surplus]

Originally Posted by theblondskeleton

Whoops haha... Well, I never claimed to be an expert. That makes sense, though. So it can operate as a kind of 'driverless' controller? And the current for each channel is adjustable similar to a MeanWell driver? Up to 48 LEDs?

If i understand this correctly now, that makes this capable of doing all the work (driving, dimming, and controlling) for just about any size build, providing there is no minimum quantity of LEDs per channel? Wicked cool! This could save DIY'ers a ton of cash on separate drivers and controllers.

Yes- Now you get it! I've literally tried to cram everything anyone would ever want into one place. It's a 150 watt/ 6 channel LED driver with it's own integrated programmable controller. The original idea was to find a way to eliminate the need to run wires "all over the place". This little board will act as a "central hub"by providing power to the leds, power to cooling fans ect.. , be fully programmable for dimming control. It also will be fully expandable to read sensors and control other aquarium devices.

If it works as designed, it will definitely be a "one stop solution" for most led builds, as it eliminates the need to purchase most of the commonly needed components.

[ugn]

6 OnSemi CAT4101 led Constant current Regulators w/ up to 1000ma output.( will drive 6 - 8 leds per string, provided total led Vf does not exceed 25 volts.)

Sounds very promising, but if you want to run 10W leds and about 4-8 of them.. this would not work i guess?

[theblondskeleton]

That's pretty incredible! Nice work! I've linked this to the FAQ as 'in progress' until you have the opportunity to test it out. I'm sure there will be a lot of builders interested in this driver.

[O2surplus]

Originally Posted by ugn

Sounds very promising, but if you want to run 10W leds and about 4-8 of them.. this would not work i guess?

Driving 10 watt leds shouldn't be a problem. All you'd have to consider the Vf of you particular 10 watt led. Most of them, that I've run across, have a Vf of around 12 volts, so you should be able to run 2 of them in series on each chip. Each CAT4101 is rated to handle up to 1000ma at 25 volts maximum ( 25 watts total), so driving (2) 10 watt emitters at 800ma would yield approximately 20 watts per string. That scenario would let you drive (12) 10 watt emitters from this driver design. I have personally used 2 CAT4101's wired in parallel to drive BridgeLux 50 watt emitters, so this driver design could be configured to drive 3 of those same 50 watt emitters.

[d3snoopy]

Love it. Tagging along. Once you have it running well, you should get a batch of 20-40 made & sell em. I'd buy a couple.

[ugn]

1000mA should be enough for the most guys here, but is it possible to increase the voltage, for example up to 48 volts?
So each string could give out max 48 watt.

[O2surplus]

Originally Posted by ugn

1000mA should be enough for the most guys here, but is it possible to increase the voltage, for example up to 48 volts?
So each string could give out max 48 watt.

Nope- the CAT4101 driver IC is only rated for 25 volts. That's why there's 6 of them on the board. The nice thing about shorter strings is more control or higher resolution when dimming.

[hamato]

Is there any cutoff for the CAT4101s? That is one thing about the Meanwells I don't like, they cut out at about 30% which is still pretty bright when driven at 800ma max.
Also I wonder about moonlight support. Something like 2-3 LEDs running off one channel fully dimmable would be nice.

[jcgd]

Nope. I have a bunch of O2's old drivers with the cats. No cut off. Mine dim all the way off and all the way on. I was warned that they make not dim if the LEDs aren't warned up, but no problems so far.

[O2surplus]

Originally Posted by hamato

Is there any cutoff for the CAT4101s? That is one thing about the Meanwells I don't like, they cut out at about 30% which is still pretty bright when driven at 800ma max.
Also I wonder about moonlight support. Something like 2-3 LEDs running off one channel fully dimmable would be nice.

There's no abrupt cut-off with the CAT 4101's. They can be made to dim to a fraction of 1%, provided the PWM signal frequency has been set low enough. 150Hz seems to be that magic number. It's too bad only 2 output pins on the arduino can be configured to PWM with a frequency that low.

[d3snoopy]

Originally Posted by O2surplus

There's no abrupt cut-off with the CAT 4101's. They can be made to dim to a fraction of 1%, provided the PWM signal frequency has been set low enough. 150Hz seems to be that magic number. It's too bad only 2 output pins on the arduino can be configured to PWM with a frequency that low.

Forgive my ignorance, but aren't lower PWM frequencies easier to do? I know there is lots of code out there related to servo control running at ~60Hz - I'd think that you'd just have convert from a "built in" PWM philosophy to a manually-programmed PWM where you program discrete pulses at a given length?

[O2surplus]

Originally Posted by d3snoopy

Forgive my ignorance, but aren't lower PWM frequencies easier to do? I know there is lots of code out there related to servo control running at ~60Hz - I'd think that you'd just have convert from a "built in" PWM philosophy to a manually-programmed PWM where you program discrete pulses at a given length?

If I'm not mistaken, I believe the normal default setting for the PWM frequency coming from the Atmega chip is set at 5KHz. The Pwm frequency can be adjusted from there- using the programming software. It's just a matter of plugging in the appropriate numbers to the programming code.

[d3snoopy]

Originally Posted by O2surplus

If I'm not mistaken, I believe the normal default setting for the PWM frequency coming from the Atmega chip is set at 5KHz. The Pwm frequency can be adjusted from there- using the programming software. It's just a matter of plugging in the appropriate numbers to the programming code.

I'm saying that I think the approach that most of the servo control guys take is simply to do something like:

Set N = 1.5ms (servos typically receive signals in the 1-2ms range @ ~60Hz)

Loop:
Output a N ms pulse
Delay 18 ms
goto loop


So, if you adapted it to your purposes, you could do something like:

Set DutyCycle = 0.2

Loop:
Output a (DutyCycle * 7) ms pulse
Delay for [(1 - DutyCycle) * 7] ms
goto loop

Obviously, you'd have to account for everything else you wanted the controller to be doing... but with low PWM's everything happens slowly enough that you can just manually program the pulse widths and delays.


I don't know much about Aurdino, so I'm not sure how tricky it will be to get all of the multitasking right... especially when you want to be able to vary all the way from 0 to 100% duty cycle. with servo control, you can count on having at least 18ms between pulses... with a fully variable duty cycle you have to adjust where you get your extra clock cycles depending upon the desired duty cycle.