Thanks for reading. I made a simple led flash pattern on an Attiny85. I'm a novice at electronics so please forgive my ignorance.
The Attiny85 only offering 40mA per out. I wanted to use some bc337 on the outputs to allow more leds. The current set up uses two pins as outputs, with 4 leds on each output at 10mA a piece. Plenty bright for my application. But I wanted to double the lights from 4 to 8 on each output.
I have the transistor base connected to a 560 ohm resistor at the Attiny85 outs. The emitter is grounded, and, my leds are in groups of two, parallel, connected to +5V with corresponding resistors. The led cathodes are connected to the collector of the transistor.
Everything is working. But my question is this. For the life of me I cannot determine what "actual" resistor value I need at the base of the resistor. I just guessed with the 560 ohm one.
So two questions. How many mA of output does the bc337 offer? I'm still trying to familiarize myself with datasheets and am unsure.
Also, how can I determine the lowest possible resistor value for my transistor base in my circuit?
Thanks for your insight and patience. Much appreciated.