iRobot Roomba 521 bumper sensors

[Risen91]

Hey all!
I'm trying to connect an Arduino up to the right/left bumper sensors on an iRobot Roomba 521 so I can detect when it collides with an object, but I'm pretty new to electronics and programming.

I have disassembled the roomba and found the wires leading from the bumpers (images below) but I could use some advice on how I would connect these up to be read by an Arduino.

Left Bumper:



Right Bumper:



Connector:


If anyone needs more images or information just let me know . I imagine that the bumper is initially on a low signal and when it's pressed (hits an object) the signal goes high? Would I just be able to splice a wire onto one of these cables and put it straight into the Arduino and read the data?

Apologies for the lack of electronic knowledge, I see some people on here doing crazy advanced things with Roombas I'm trying to learn a bit via this project. If anyone can point me in the right direction or give me some advice I would be very grateful!

Thanks in Advance!

[vic7767]

Here is a link to a post provided by Gordon that may help you in your efforts.

http://www.robotreviews.com/chat/viewto ... 36&p=82057

[Risen91]

Here is a link to a post provided by Gordon that may help you in your efforts.

http://www.robotreviews.com/chat/viewto ... 36&p=82057

Hey vic7767 thanks for the reply! Gordon's post now has me a little worried as most of what he said is a little beyond my knowledge. In my mind I thought it would be a little more simple such as just soldering on a couple of wires to the sensor and inputting that straight into the Arduino to read the sensor state. I see there is 4 wires coming from the bumper sensor but I'm not entirely sure what each of these wires does. Apologies for my lack of understanding here, I'm still pretty new to electronics.

[vic7767]

Give me a day or two & I'll have some info and pics to help you along.

[Risen91]

Hey! so I think I have finally made some progress!

I came across this information:
https://www.schneordesign.com/diy/diy-i ... mba/9beep/
and also:
https://www.robotshop.com/community/blo ... sor-boards

Now I understand that the bumper sensor is a IR Tx/Rx with the "bumper" blocking the IR light from passing when pressed (Roomba hit an object).
Image of the bumper:


I can see the traces at the bottom of the PCB leading to the emitter which is according to the guide furthest away from the soldered points and the top two traces being the Rx, closest to the soldered points.


So now I just need to understand how to connect the phototransistor to the Arduino and read the data, possibly using the IR library. Since the Arduino will be in the area of the Roomba where the brushes used to be (removing all the cleaning capability for now) I was looking at the best way to path the wires to that area from the bumper sensors. Since the Roomba main PCB has a couple mm gap under it I was thinking of just running it under there and making a hole in the plastic right into the compartment.
Images below shows where I was thinking of running the wires (red) and making the hole (green):


I doubt I will commit to doing this today so if there is any advice on my plan so far just let me know maybe better wire/hole placement or an easy way for the Arduino to read the data.

I never owned a Roomba or did much electronic stuff before this project so it's a pretty steep learning curve. I'm amazed how modular and well thought out the iRobot Roomba is and how simple it is to take apart and assemble.

Thanks again!

[vic7767]

OK here are the testing results for the Bump sensor.

The image below has 4 pins that are numbered from 1 through 4 starting on the left.

When the bump sensor bumps an object, pin 3 goes from low - 0 volts to high - 5 volts