I have a project where I am making a Portal Gun Prop from Portal, but I am new to using arduinos. So I do not understand if I am doing this right.
I am aware that my RGB LEDS Diodes need Resistors, and I am unsure how to calculate that with these diodes.
I want to be able to switch the lights between Orange, Blue, and White using 2 push buttons. (1 for color, between blue and orange, and 1 for white to override blue and orange. )
RGB Diodes -
R- VF- 1.9-2.1 V λ 620-630 nm
G- VF- 3.0-3.2 V λ 520-530 nm
B - VF- 3.0-3.2 V λ 460-470 nm
9 Diodes.
6 in a series, 3 in parallel with series
The LEDs can't be in series without higher voltage. i.e. Two 2V LEDs in series needs 4V, plus the voltage drop across the resistor. And RGB LEDs don't work in series because you can't isolate each color in series.
In parallel the current adds-up and the "absolute maximum" from an Arduino pin is 40mA, so with 4 LEDs in parallel you should limit the current to 10mA or less, and that's "worst case".
The voltage divides between series components. For example, with 4.5V across a resistor and a 2V LED, the resistor gets 2.5V. Use Ohm's Law (Resistance = Voltage / Current) and plug-in the desired current to find the required resistance.
You may need to add transistor drivers for more total current.
Your frizzing thing is hard to read, a real annotated schematic would be easier to read. Instead of transistors take a look at using MOSFETs, they will not lose as much energy as they will not be burning 0.7 volts for each transistor in the chain. How long does this run from one charge. Using higher voltage battery system would make the design easier. An important rule for Arduino: "A power supply the Arduino is NOT!"
When using LEDs you need to determine how much current you want to go through them. There are many charts that will tell you the forward voltage of them, but it is in a range. I just use something in the middle as my circuits are not that critical and I am lazy with math.
When putting LEDs in series you need to add the forward voltage of each of them and be sure it is below the power supply voltage. Subtract the difference of there sum from the power source voltage. Then using an Ohm's law calculator you can calculate the current you need. In a series circuit the current is the same through all elements.
Parallel LED's present a challenge. Unless matched there forward voltage is not the same so you need a resistor or some current limit device for each one. Generally 20mA is the max. At this point you can see why a higher voltage makes it easier.
Using N-Channel MOSFET in each color will take the load off of the Arduino. Be sure to put something in the 10K or higher range from the port pin to ground, this will be sure it is off during reset etc. Then use something in the 50 - 100 (it would work without) Ohm range between the port pin and the MOSFET gate.
In your large array you can configure it with 6 LEDs in series and each string of six having a series resistor. You will have to check forward voltage to be sure.
When looking at MOSFETs be sure they are on at about 2-3V (Vgs). Not all MOSFETs labeled logic level are and many more will not work with 3V3.
This should get you started. If you are looking for a CAD program KiCad is great but it is not a one night learn how to use it program, it is a full set that will go from schematic capture to PCB (Printed Circuit Board). Most important take your time and have fun!
