Just to share... (5 x 10watt RGBs) no current regulation!

[cjdelphi]

http://www.youtube.com/watch?v=2bb7zUUN8yI

Using just 2n2222s and a 68ohm resistor on each of the base pin, it pulls just under 2 amps when cold.... and sadly even when warm, it still pulls around 2amps!  - i've only had it running for about an hour tops so hopefully it gets brighter as it gets hotter lol (68ohm resistors to the base, and no current limiting resistor either on the emitter or collector, they are all sinked via an NPN)

This was simply a test to see what happens if you supply rougly 120ma to each RGB segment of the LED and when it got hot, would it rise to say 200 or even 300ma?... sadly not and if did, it has 200ma of leeway.

either way, it's damn bright for 20watts and hopefully Mr Grumpy is right about high powered LEDs increasing in current when hot because it'll only get brighter and stay well within the 800ma spec limit of the 2n2222's .

[elac]

cjdelphi,
On each color:
What's the max PWM value that you use for a 120mA limit?
What's the voltage drop across the color segment when 120mA is being drawn?

I tried this and to maintain a 200mA draw limit on the green segment I had to use 72 as a max PWM value.

[mmcp42]

my eyes hurt now

[cjdelphi]

Elac, I'm using someone's library, when I get on my desktop I'll supply the info.

I had this thing running all  day and when I felt the heatsink it was just on the verge of being too hot to handle, but you still could pick it up, and sadly it was still pulling the same amount of current as it was when cold!


As long as the heat is dissipated from an LED, the current refuses to rise when propetly heat sinked... (10watt rgb / 300ma/r/g/b)

[elac]

Thanks that will be great.

[elac]

cjdelphi, been back to your desktop lately?
Still hoping you'll post the sketch you used to achieve this.