Using a Raspberry Pi and 5V I want to use 25 IR LEDs (5mm LED, 940nm wavelength, 20 degree beam width, 100 mA continuous, 1000 mA pulse, Approx 1.6V forward voltage; http://www.exp-tech.de/super-bright-5mm-ir-led-25-pack) in parallel using 8 pairs of 3 LEDs each pair with a 2 ohm resistor and one single LED with a 36 ohm resistor.
This tutorial is my basis: https://www.sparkfun.com/news/1396
You can see that in this tutorial a npn transistor is used with a resistor R6 of 330 ohm.
I've ordered this PN2222 transistor (http://www.exp-tech.de/npn-bipolar-transistors-pn2222-10-pack).
My question is, once I have all LEDs and their resistors (2 and 36 ohm) in place, how would I need to install the transistor(s) and how would I calculate the R6 resistor for my example?
Here is the LED datahseet: http://www.adafruit.com/datasheets/IR333_A_datasheet.pdf They are just turning on/off all at once. For my project I would need to get enough IR light in order to brighten up a whole room of 15 and up to 35 square meters, if less LEDs will produce enough IR light, I'm happy with it. For video recording a Raspberry Pi NoIR Camera will be used. The system will be time-controlled, the LEDs are supposed to run probably 4-5 hours for each time-frame. @KyranF: You're right that I was not aware fo this as this is acutally my first project including more than one LED.
Here is a first try to visualize the solution.
Does this setup with the mentioned LEDs and a MOSFET sense? Do you think 14 LEDs of this kind would be enough in order to brighten up a whole room?
This is my current set-up, which seems to be wrong as well. I'm not getting the IR LEDs to lighten up.
Important hint: I'm using 33 ohm resistors for the LEDs as the LEDs I've finally bought are using 50mA instead of 100mA as the ones listed before. Here is the new Datasheet
My Python code looks like this:
import RPi.GPIO as GPIO ## Import GPIO library import time ## Import 'time' library. Allows us to use 'sleep' GPIO.setmode(GPIO.BOARD) ## Use board pin numbering GPIO.setup(7, GPIO.OUT) ## Setup GPIO 4 Pin 7 to OUT GPIO.output(7,True) ## Turn on GPIO 4 pin 7 time.sleep(5)## Wait GPIO.output(7,False)## Switch off pin 7
The wiring looks like this:
Here is an overview of the GPIO setup: