iRobot Roomba virtual wall DIY

by saint187 Sep 16, 2018
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Hi Tumppi77
I did some research and I think that the problem is, that the (Sparkfun) Pro Micro does the output on pin 5:

// Define which timer to use
// Uncomment the timer you wish to use on your board.
// If you are using another library which uses timer2, you have options to
// switch IRremote to use a different timer.

// Sparkfun Pro Micro


//#define IR_USE_TIMER1     // tx = pin 9
#define IR_USE_TIMER3       // tx = pin 5
//#define IR_USE_TIMER4_HS  // tx = pin 5

Have a look at the site above - I think this should help.

Hello. I can't make it work. It just doesn't send any signal. The program upload goes without any problems. Wiring is correct, components are intact. I am using Pro Micro Atmega32u4 board, can it be a problem?
I checked with the oscilloscope and there is no signal on pin3.

I already ade one, works very well, great work! I will post a "make" later.

Hi there... says you added the code.... I can`t see it?

Hi stainless,
the file is an arduino IDE file. It is included in the download files (iRobot_virtual_Wall.ino). You will also need the "IRremote" library to get it to work. The LED is connected to pin 3 of the arduino.

Hello, great design ! How do you calculate the good resistor value for the IR led please ?
I found this on AliExpress for the IR led : https://fr.aliexpress.com/item/10Pcs-5mm-940nm-IR-infrared-LED-Lamp/32649212948.html
Thank you for your answer.


I think you should use a more powerful irLED. I am using a 100 mA irLED and a 47 Ohm resistor and my virtual wall is nearly 4 to 5 m long. If you use the irLED mentioned in your post, expect 1.5 to 2 meters...

Thank you for your help :)

Hello MoogyFR the correct resistance for this LED would be 270 Ohm. The LED works with a forward current of 20-30mA and the voltage from the Arduino is 5V. You can calculate the resistance like this: R=U/I -> 5V/0,02A = 250 Ohm. The next resistance in E24 would be 270 Ohm. Ihope this can help.

Thank you for your answer !