hi,

I think its the transistor which is of a high current value. because its a current controlled device, a high current capable transistor would draw a relatively high current at its base. port 1 has internal pullups( and an FET for pull down) but they may not be strong enough for your transistor. use a BC 547/8/9. this transistor is good enough for low power, low freq switching.use a 1k resistor between the port and the transistor base.

I have used this transistor with port 1, with a PWM output to drive the backlight LED of an lcd module( i wanted to control the brightness of the backlight). it works great and i can get the complete FULL to NO brightness range. I hope this solves your problem.

kodi