Roomba: cleaning the cliff sensors

So, I have a Roomba. When I learned about it, I got one mostly because it is a ROBOT, and secondly because it might be useful. And all during the first year of ownership, I tried to be a responsible adult and not jump and open it up for no reason. I waited until Roomba stopped working complaining of the edge after bumping into a darker pattern on my carpet. Closer inspection revealed that cliff sensors were dirty from inside.
An excellent excuse for a nerd to open up a Robot. The first time I did procedure a year ago, following the directions I found on the internet. It was success, Roomba’s cliff sensors were cleaned, and it continued to work nicely for almost a year.
The trouble is, I live in a desert, meaning dust is everywhere. So cliff sensors got dirty again. This time, I could not find the directions on the internet( who knows what happened to the original page) So, I decided to document my cleaning and make a reference page for the next year, because, I’ll need it.
And here they are, directions how to clean the cliff sensors on Roomba.

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This is my Roomba. Yeah, I have pets, a dog, and two cats. If you have Roomba from the same family, it might have a handle. Mine does not, probably because it makes it a bit more resistant to the pets.
Anyway, turn it upside down and remove the long yellow brush.

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This step is recommended for periodic cleaning as well because pet hair gets tangled below the yellow part. (And to be honest, my own hair too). Sometimes in such amounts that brush gets stuck.
Next step is removing the plastic cover.

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You can use the same size Phillips screwdriver as for yellow brush. The screws at the cover are captive, meaning, you cannot remove them from their holes, so do not try. Plastic breaks, you know.

I took a photo before dusting the surface. Dust is everywhere at the surface that is usually bottom. Meaning, that dust had to work hard against gravity to end up there. You can imagine how much dust there was on the cover I removed.

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Next step is to take out the battery. You do not have to worry about memorizing the correct way to put it back in, it benefits from idiot proof design.
Mine was completely empty because I left Roomba sitting outside its port for days waiting for a slot in my schedule. I do not recommend that, because, trust me, when you put it back together first thing you will wish to do is check does it work. Difficult to do with a dead battery. So charge the little Robot before you clean it.

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Next step, removing the bumper.

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You’ll need smaller Philips screwdriver for that task. At this point, I recommend you to prepare small containers for screws you took out. There will be around 4 difIMG_0812ferent groups of screws, and you do not wish to mix them up. I used tiny dipping bowls, simply because I was cleaning it in the kitchen and those were handy.

Next step is the most nerve-wracking for me. Removing the plastic cover. I was afraid I will break the blasted thing. It is always tricky to find a correct amount of force to make those hooks release their hold but remained whole in the process. Especially today, when a quality of products deteriorated (due to budget cuts) and products are simply not meant to last for years.
Start by flipping Roomba right side up. The wheels are springy so the robot will react to pressure applied on top of it.
Remove the trash container, as usual. And then try to pry the plastic cover off.

Carefully.

It is held by small plastic hooks around an outer edge of it, so you have to pry carefully those open.
I have to repeat how much I hate this part, just because I know that breaking one of those little hooks would ruin the whole thing.
Photo shows one of those hooks. Inner edge has no hooks, but it sticks because it has an a hanging edge that lays in a groove. When you free outer edge, just pull up. Nothing will break.

Next step is removing the bottom plastic cover. You can see on my robot, that there is a groove where the handle on other models rests. I do not have a handle, so in this step, I have to deal just with 2 sizes of screws.
If you have a handle the screws just next to the handle will be a different size as well. For me, I just had to take care of one smaller screw, the one closest to the buttons marked with schedule and clock.

Be careful how you remove the cover. The wires that connect motherboard with the infrared sensor on the bumper pass through a small notch. So do not tug, but carefully remove wires from the notch.

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Next step is easy, remove the central part. There are 3 parts that are not held by any screws.

The last part is held by 4 screws. (And yep, that’s motherboard you can see below central part.)

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Next step is to remove the plastic cover that protects the motherboard. Or I would say, it should protect the motherboard, but does not do a good job. There was dust under it, as well.

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And finally, removing the motherboard.Yep, to clean cliff sensors you have to remove the motherboard. I could bitch how the placement of sensors is badly engineered, but I have to admit, I use this ‘engineering solution’ to check up on Robot’s insides. 😀

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When you remove the screws that hold motherboard (5 of them), do not tug it upward. There is just too many wires connecting sensors to it, a thin, flimsy ones. Carefully remove connectors from the motherboard. Do not fret, those are idiot proof too, each one is different and can fit only in proper hole. Do not use wires to pull the connector out. Yeah, it is tempting, but do not, you’ll loosen the contact. If you cannot grab the little white holder by your fingers, use tool, a small metal spatula like tool will do.
Then carefully lift the motherboard up. There are more wires connected on the bottom side.

Remove those connectors as well. I used my fingers, an advantage of owning small female hands.
The coil of copper wire you see in the photo was full of my pet’s hair. So although this is a pet series Roomba, it is still open enough for animal hair to sneak in.
On the right is the picture of one of the hairs stuck in the coil. I removed the other ones before remembering to take the photo. :-/
That particular hair belongs to my dog.
Anyway, now we’re getting close to cliff sensors. Turn Roomba upside down (wheels up), and start working on removing the sensors. I used a cutlery knife as help with this step. There is a plastic hook that holds each of 4 sensors in place. To free sensor from the hook, put the top of the night (or any other flat metallic tool) between sensors transparent cover and body of Roomba. And push sensor away from the body of the Roomba. At the same time gently start pushing downwards with your finger. Eventually, the sensor will get loose. (You can see loose sensor at the left side of the photo.)

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Front two sensors, near the spring that makes bumper bouncy have an additional issue. Bumper spring wraps around the same plastic element that holds sensor, so you’ll have first to unwrap the end of the spring and then pull the front sensors out. IMG_0802.jpg

The spring will easily snap back in the place after you remove the sensor.
Now, cleaning the sensors itself. My guess is that they should be quite well sealed. From 4 cliff sensors on my Roomba, only two had dirt inside the transparent cover.

Those ones I opened up, removing the  cover and blowing an air inside to clean them up. I recommend using air, simply to avoid potential damage to the sensitive sensors. For those ones who do not know, there are pressurized cans of air that you can use for this purpose if you do not have an air compressor handy.

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That’s it. Now, the biggest challenge is to put everything back together. With the second time in a row, I managed to accomplish that, simply backtracking through the previous steps.
And happily, I did not end up with any spare parts. 😀
As I said, the battery was empty because I left Roomba for 3 weeks outside its dock, so I had to wait 24 hours to test the quality of my messing with robots.
Here is the video of my little robot happily working. No dark patches on the carpet could stop it now.

 

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