Roomba 550 / 5xx Cliff Sensor Disable

If you're like me, an owner of a Roomba 550 / 5xx and have a dark carpet or dark tile on the floor, you'll have noticed that the Roomba doesn't like cleaning them, in fact it can cause a lot of problems that it can't recover from.  After doing some research I found that the Roomba has a problem with dark colors, it causes the cliff sensors to be confused making it think that it is about to fall off a cliff.   The  Roomba will try to back up and get away, but that is not always the desired effect, especially if you  want it to clean a dark carpent.  Well, as long as you are sure that there are no stairs or cliffs in the rooms you're cleaning, there are some ways to disable the cliff sensors.

The first method is the paper and tape method.  I used this for a while, and it seemed to work OK.  But getting the paper in exactly the right location, making sure the sensor are clean was a bit of a pain.  What even made this worse is that the paper would get dirty or damaged over time and stop the fix from working.

The second method is a change in the hardware that will disable the sensors.  This is the method I was moving toward when I discovered a slightly easier solution that doesn't require changes to the hardware.  There were no directions on the net to show step by step how to do this, but I'm an Engineer and like to tinker and can typically get myself out of a jam if I'm mucking with something like this, soI was more then willing to try it.  But this knowledge also lead me to the fix below.

First a quick description of how things work and the change.  The Roomba 5xx cliff sensors work by transmitting an IR signal and bouncing it off the floor.  If the signal bounces off and returns, everything is OK.  But if the edge of the Roomba is over a stair, it will not reflect and the Roomba will stop, and backup.  The change I describe is to take the transmitting component and the receiving component and put them together so that they ALWAYS receive the signal.  Simple.  The hardware fix listed above will cut the wires to these sensors and connect 1000 ohm between them to do the same thing, but this way, you don't need the resistors, you don't need to cut anything, and you don't need to know  how to solder.  Without further delay, here are the 42 easy steps to follow.

1.Place the Roomba top down on a solid work surface.

2.Remove the four screws holding the bottom in place.

3.Remove the screw from the rotating brush, then with a slight tug, pop off the rotating brush itself.

4.Lift off the bottom.

5.Take out the battery, there are no screws here, just lift it out.

6.Take out the 10 screws on the bottom of the bumper.

7.Lift off the base of the bumper now that the screws are removed.  Place it to the side.

8.Turn Roomba over and slowly lift off the front bumper.  Be careful, there is still a wire connected to the bumper. 

9.Gently turn the bumper over, and unscrew the base station sensor.  Note the other half of the sensor on the top will fall off, that's fine. Now you can remove the front bumper completely.

10.Lift up on the gray decorative cover until the tabs prevent you from lifting further, press on them with a screwdriver slightly to release them.  Work from the front toward the back. 

11.Lift the handle and slide the cover all the way off.

12.Remove the 11 top screws.

13.Now gently pull on the outside of the case with your fingers while pressing the  center (near the buttons) with your thumbs.  This will release the case cover.  Lift straight up and remove the cover.

14.Lift off the silver decorative ring around the buttons; followed by the button cover plastic and finally the flexible plastic inset. 

15.Remove the four buttons holding the button component in place.

16.Lift the button component and the clear plastic off the motherboard.

17.Unplug the four connectors at the back of the motherboard.

18.Unscrew the five screws that hold the motherboard down.

19.Now lift the motherboard and the front sensor bar up slightly and shift it back just a little.

20.Locate the four clear sensors; you are going to have to repeat the following steps for each of the sensors.  Steps 21 to 26.

21.With a flathead screwdriver press along the edge of the sensor (gently), where the arrows are pointing, and pry up the sensor top (the black part, not the clear).

22.You can now lift the sensor casing all the way out of the clear plastic of the sensor.

23.Gently pry apart the sensor casing, it should pop apart leaving two black plastic parts, one with wires.

24.Remove the transmitter and receiver from the sensor casing.

25.Tape the receiver and the transmitters together so that the two ends are right next to each other.  The type of tape doesn’t matter, the wires are all covered and they don’t get hot.

26.Place the taped bundle back into the clear plastic of where you removed the sensor casing from – do not reinstall the black sensor casing.

---- I am not posting images from here, they are just the disassembly instructions in reverse ----

27.Replace the motherboard and the front sensor bar back to their original position, and secure with the five motherboard screws.

28.Reconnect the four connectors at the back of the motherboard.

29.Replace the protective clear plastic.  Make sure it is aligned correctly otherwise the buttons won't be able to be screwed down.

30.Place the button unit where it should be, lining up the screw holes and then screw it down.

31.Put the flexiable plastic covering , the smoky gray plastic and finally the silver outer ring over the buttons.

32.Set the top cover back in place, making sure that the front sensor's wires are set correctly.

33.Secure the top cover with the 11 screws.

34.Lift the handle, and replace the decorative cover back in place.  Pressing down along the edges to secure it.

35.With the front bumper upside-down reconnect the front sensor and secure with the two screws.

36.Flip the front bumper back over and set it in place.

37.Flip Roomba over.

38.Place the front bumper edge back in place, making sure it is aligned correctly.  Then secure with the 10 screws, working from the middle to the outside.

39.Replace battery, Roomba will make the wakeup sound.

40.Secure bottom cover with the four screws.

41.Reconnect the spinning brush with the single screw.

42.You will need to set the time and your schedule of your Roomba.

You're done, Roomba will now always be happy on dark flooring.  It won't be so happy if it discovers stairs; so make sure you don't let it!

Good luck, and have fun!