DIY infrared transmitter (Arduino Uno Programming Basics)

DIY infrared transmitter (Arduino Uno Programming Basics)
In this Video I show you how to drive a 100mA infrared diode using an Arduino Uno R3.
I am using a transistor amplifier circuit and explain every component selection in detail.
I also show you how you can use multiple resistors to match a desired value.
In the end I use the setup to control both ONKYO AV Receiver and BENQ Beamer with the Arduino using the IRremote library in the Arduino IDE
00:00 Introduction
00:12 electronics
08:35 software
12:38 exercise
16:34 field test

[@jimg9294]

Excellent! Thank you.

[@bob_mosavo]

Thanks 👍
I'd put a 1Meg pull down resistor from the base to ground 😉

[@playduino]

It wouldn’t hurt for sure but will it help?
When using mosfets you will need this resistor to keep the gate from floating when Arduino is in a high impedance state. The NPN needs a base current to become conducting, so the additional resistor should not be required.

[@bob_mosavo]

@@playduino Even a BJT is a voltage controlled device. If you don't believe me, just read The Art of Electronics and/or the Ebers-Moll equations. It's much easier to use the calculation approximations for current with BJTs, which is why almost everyone thinks BJTs are current controlled.
Also, why didn't you choose to go with an emitter follower circuit? I think the calculations could have been much easier, and I believe you would not have to use specific items from a BJT data sheet. Anyway, that's just my two cents 😉

[@playduino]

thank you for sharing your thoughts but I am not convinced, yet 😅
I looked into Art of Electronics Third Edition. On page 76 you find the circuit that I used to drive an LED.

[@bob_mosavo]

@@playduino Please take a look at the video titled "BJTs are VOLTAGE-Controlled Current Sources!" on the channel "Lantertronics - Aaron Lanterman"
I think that may help convince you 😉

[@playduino]

Thank you for sharing the video 🙂
It's an interesting approach to think about the BJT as a voltage controlled device. And it seems accurate. However even if there was a high source impedance voltage on the base that is high enough, it would immediately break down due to the "leakage" current of the transistor into the base. So I still do not see why this resistor should be required. 😅