I'm not sure if this question belongs here or in your "Ask an Engineer" section but since it is somewhat related to this device I'm going to post it here.
I've built two or three Arduino-based gadgets that emit IR remote control signals but I've never really been confident that my driver circuit was giving me optimal results. I know nothing about circuit design except a rudimentary understanding of Ohm's law with almost no experience knowing how to apply the damn thing :-)
What I'm saying is I'm a total noob. My background is programming not electronics.
I've tried googling websites for transistor circuit design, LED driver circuit design, and a variety of other things and they are all over my head even though they seem to be pretty simple. One website directs me to the design page of the TV B-Gone gadget here http://www.ladyada.net/make/tvbgone/design.html
I think I burned up the transistor the first time I tried that single transistor driver circuit. Even an idiot like me should have realized the TV b-gone runs off of 3 V and I'm using 5 V. Then again I could've hooked it up wrong on the breadboard. This schematic for the single transistor version says use a 120 ohm resistor. I picked a bigger value (400 or 500 or so I forget). The gadget works but the range and directional angle seems to be limited.
What I thought I would try to do was emulate the more advanced version of TV B-Gone that uses multiple LEDs and transistors. Ultimately here is what I would like… I want two IR LEDs. One of them to be the wide-angle, the other to be the narrow angle. I went essentially half of what the latest TV B-Gone has. I've got a pack of PN2222 NPN transistors that I bought from here. I think I bought my IR LED RadioShack number 276-143 or I might of purchase one from here. I have no idea if it's the narrow angle or wide-angle version. You guys say that the IR LEDs that you sell are the ones that you use in this kit and that they are the 20° angle versions. But you don't appear to sell the other version that the TV B-Gone kit uses. I don't know what they angle is on the RadioShack version.
So finally I get the point of my message here…
1) If I'm using the single transistor driver circuit on a 5 V system like Arduino, what value should the resistor be between the pin of the Arduino and the transistor?
2) If I decide to use two transistors to drive two IR LEDs, can a single output pin from an Arduino drive two transistors and what value should the resistors be?
3) if an Arduino cannot drive two transistors and I decide to add a PNP driver to the drivers (sort of a one half TV b-gone circuit) is the value for R1 which you show as 1.0 K still correct even though I'm only driving two NPN transistors instead of four? And more important keep in mind I'm working on 5 V instead of 3 V. And do I need the optional R2 10K resistor under this circumstance? If so what should its value be in a 5 V circuit?
4) Just a comment… Why don't you sell both types of IR LEDs the wide-angle and the narrow angle?
I know the questions I'm asking are somewhat above and beyond the call of duty for a support forum. It's not you guys job to design my secrets for me. But this seems to be the kind of thing someone around here would know off the top of their head or can spend 30 seconds doing some math and could answer for me.