transistor always open?

hi everyone,

i've made some code (not rly relevant) that allows me to control an rgb moodlight, now when i work with a simple led their doesn't seem to be a problem,

but now I've used a ledstrip with 3 transistors bc547, now the wierd thing is i can alter the colors with pwm but i can't put them out, i mean the leds are always burning rly softly, and red is the whorst, i've read somewhere that blue and green require more power then red but i don't know why my transistor would still be 'a bit high' even when my arduino pin is on low,

thx in advance

Probably need to see a schematic of your setup along with whether this is a common cathode or common anode type led. Code may be necessary as well to help determine if you're driving it correctly.

http://www.circuitsonline.net/schakelingen/sch/000034.gif

this is the one i used, 3 times;

the data line is the pwm pin from arduino and on the + side is the 'common' side of the led strip, then the color is connected to each transistor

What type of LEDs are you using? Are they single color LEDs or is it an RGB LED? If it is RGB, is it common anode or common cathode?

Since you have a 1k resistor limiting current to the LED when the transistor is 'On' there seems little point in having the transistor at all.
Half the resistor to 470 (nearest common value to half of 1k) ohms and wire it straight to the Arduino Pin and forget the transistor. It will work at around the same brightness as 9v with 1k.

It should go off completely if the schematic is wired up like you show. Make sure you have connected the ground of your 9V supply to the the ground of the arduino.

Hello, i don't want to say you circuit is right or wrong cuz i know someone is going to shout at me but, how about replacing the 4k7 with the 1k and replace the 1k current limiter with a resistor around 600ohms, this is based on 12v - 2v (Led Working Voltage) = 10v divided by 0.015 (15ma Led current drive) = 666 ohms, adjust the values to your particular needs.
Have a look at the ULN200xx range of darlington drivers, 500ma each channel, more than enough, usefull for driving motors too

yeah i know my resistances are already different, I'm using 1 rgb strip,

but the wierd thing is when the arduino pin is at 0 the leds still shine (a bit)
so even with no current gooing over the transistor it stil lights the leds up

Sure the BC547 is wired up right? it's a ebc variety.

Normally the shown circuit should work without issues.

yeah i think its right cause on lower voltages (6v) it works but from 7.5 and above the led stats to shine a bit