Fading Troubleshoot

Hey there!

I am trying to run a LED strip with external power and a BD243c (Data sheet: http://www.bucek.name/pdf/bd243.pdf).
The Arduino is fading nice between 0 and 5V but the LED strip is only doing weird stuff. No clear pattern visible. I tried a 550Ohm resistor bevor the base but no effect.
Transistor should be wired correctly, changing Emitter and Collector had no effect either.

Any help? Thanks a lot

Did you remember to connect the grounds?

Yes, all common grounds

Not a very good transistor for a LED strip, unless the strip is very short.
Low gain, high saturation voltage.

Better get a logic mosfet.

What is the current draw of the strip.