Hello, first let me mention I've been searching and reading for over a week to try to understand what I need here and am still having a little bit of trouble. I do understand much better already tho!
I'm using a 2N3904 transistor to switch the ground for the LED's in my light cube. I've got blue led's with 100Ohm resistors on the positive side before the LED.
My question is...
What value resistor do I need on the switch leg (middle leg, still learning all the terms, sorry) to switch the transistor open so it can flow freely to ground?
I've found a few formulas but theyre different and i'd like to understand why i'm doing what i'm doing, not just adding numbers...
I'm getting stuck trying to calculate the resistor I need to use to obtain full saturation (I believe this means that the transistor is open as much as it is able to?) so current can pass through freely when its switched on.
My source voltage is coming from my arduino currently (soon to be an AVR chip but just trying to start simple as i'm learning) and is 3.3V.
Here are the values that I've gathered...
For the 2N3904
Low Current Max 200MA
Low Voltage Max 40V
Vce(sat) 0.2 (i believe this is correct? Just learned what this is last night...)
LED Specs (blue 5mm)
3.0-3.2 forward voltage
24mA current
Arduino Power Output
3.3v @ 50mA
I would like to run 20mA through each LED and only one will be lit at a time.
Please let me know if i'm unclear about what i'm asking or if I need to find any other values to get the calculations i need. I'm a bit of a newb but very driven to learn and don't mind reading and searching!!
I'm using a 2N3904 transistor to switch the ground for the LED's in my light cube. I've got blue led's with 100Ohm resistors on the positive side before the LED.
My question is...
What value resistor do I need on the switch leg (middle leg, still learning all the terms, sorry) to switch the transistor open so it can flow freely to ground?
I've found a few formulas but theyre different and i'd like to understand why i'm doing what i'm doing, not just adding numbers...
I'm getting stuck trying to calculate the resistor I need to use to obtain full saturation (I believe this means that the transistor is open as much as it is able to?) so current can pass through freely when its switched on.
My source voltage is coming from my arduino currently (soon to be an AVR chip but just trying to start simple as i'm learning) and is 3.3V.
Here are the values that I've gathered...
For the 2N3904
Low Current Max 200MA
Low Voltage Max 40V
Vce(sat) 0.2 (i believe this is correct? Just learned what this is last night...)
LED Specs (blue 5mm)
3.0-3.2 forward voltage
24mA current
Arduino Power Output
3.3v @ 50mA
I would like to run 20mA through each LED and only one will be lit at a time.
Please let me know if i'm unclear about what i'm asking or if I need to find any other values to get the calculations i need. I'm a bit of a newb but very driven to learn and don't mind reading and searching!!