Switching with a Transistor - HELP

[stripey_horse]

ive just build two 595 co-op boards and they are working great

but im having problems switching around 12v 200ma with transistors

im using BD135 transistors and its working ok for one , but it never really goes out , only dim then bright.

i tested the output of the 595 and its around 3.4v all the time..

would someone please have a example of switching using transistors.

im going to use 1 board (around 58 channels) for a big countdown clock based on sparkfuns clock (the clock is built)

edited with diagram of current transistor switch
* im using a 470ohm resistor on the input from the 595
* V+ is 12v
* Load is around 200-300ma

[wjohn]

hi,

can you post the schematic of the current solution. That will give me, at least, something to ponder.

i am currently switching DC loads with MOSFETs, it may be another approach you may wish to consider.


John.

[stripey_horse]

ok. ive done it

attached is the circuit i came up with today for switch led light bars. 21 RGB leds in each bar.

its working great atm on breadboard.