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 Post subject: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 9:50 am 
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Location: Baguio City, Philippines
I've been using a robot vacuum for more than a year to clean and mop my floors. It was one of those "I don't really need this" appliances that turned out to be surprisingly useful. Every day it would zip around and clean the floors. All I had to do was empty it every now and then and fill up the water tank. Until that is, it started having problems.

This is what it is supposed to do:
Attachment:
robot1.png
robot1.png [ 184.94 KiB | Viewed 549 times ]


But now it was doing things like this:
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robot2.png
robot2.png [ 191.18 KiB | Viewed 549 times ]


and this:
Attachment:
robot3.png
robot3.png [ 195.55 KiB | Viewed 549 times ]


On some days it would simply stop in the middle of the room with the battery dead. This isn't supposed to happen. When the battery gets low, it is supposed to return to the dock and recharge, then go back where it left off to finish cleaning. I got a new battery and everything started working right, but only for a couple of weeks. The new battery is now dead.

My guess is that the power supply inside the vacuum has failed. I decided to disassemble it and look at the capacitors for signs of swelling. If si, I could look for someone to do a board-level repair on it. Alternatives would be to buy a new board and swap them (about $80) or buy a salvaged board for around $35.

I've decided to give up. After three weeks I still haven't gotten the thing apart. Five screws took the bottom cover off. Nine screws took the bumper assembly off. There there are 13 recessed screws to get to the circuit board and motor assemblies. I have managed to get eight of them out. I have a large set of precision screwdriver bits, but when they're in the handle they're about 1/16" too short. My toolset says it's a #1 Phillips screw. I keep ordering different screwdrivers but nothing fits. I'll admit defeat. I decided to just order a new one, but if I wait until next week it will be cheaper. I haven't decided if I'll tackle it again, but probably not.


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 10:13 am 
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Check the closet and make sure it isn't replicating itself when you are not looking.... rise of the machines and all


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 11:05 am 
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Location: Fernandina Beach, FL 32034
Alan, I feel your frustration. I usually work on vacuum tube amplifiers and am relatively successful. But as the "new" stuff gets more and more complicated, I am usually "A Lost Ball In The Tall Weeds". For instance, I have a Denon surround sound receiver that came with this house. It's about 15 years old. It had to be turned up more and more as time went on. I did some online research and it said that the microprocessor was probably corrupt and to do a reset.

I did a reset, now no sound. I tried to do an auto setup; no sound. Yesterday, I just bought a new receiver and it will be here this weekend. It looks as though "Boat Anchors" have come back into style. Frustrating... for sure.

Sorry for the hijack, just know that we are in this together.

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 1:24 pm 
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Joined: Mar Thu 12, 2009 1:20 am
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Location: Dayton, OH
I agree, they are surprisingly useful...

Any possibility of a bad replacement battery? -- particularly if its a battery from a 3rd party manufacturer.

I would of guessed that -- based on the problem diagram -- the robot was having problems "seeing". Does it have a laser on it? -- Our "NeatO" brand one has one somewhere. Since I can't see it, I presume its IR. But my point being, the laser, or its protective cover, could be dusty/dirty.

Can't help you with the screwdriver problem tho.. :)

David


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 1:53 pm 
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Location: Baguio City, Philippines
Navigate ii on is through gyroscope sensor. It maps the room every time it runs. That's also why the walls in the map are ragged. It stopped running right on the original battery and with the new one it corrected itself for several days, then got erratic and quit.

The dock voltage is good; tty he contacts are clean. I suppose it could be two bad batteries, but I suspect the charging circuit is defective. I was expecting this to be a fairly easy project, but buying tools isn't that easy here.


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 2:06 pm 
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Location: Fernandina Beach, FL 32034
I just remembered that my daughter's Robot Vacuum was very flaky on the charger. A quick scrape with my fingernail removed a waxy substance on all contacts and all was well. But I suspect you probably already checked that?

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 2:13 pm 
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Location: Baguio City, Philippines
There contacts are clean and shiny. That was my first thought.


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 2:32 pm 
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My mother has a Shark RV750N robot sweeper, but it doesn't mop the floor. Actually, it just sweeps. Anyways, it would be a rare event for that robot sweeper to dock on the battery charger when it's low on charge. Actually, it just stops period. In fact, my mother actually places the charging dock out of the way since the robot tends to get tangled in the electrical cord of the charging dock
In addition, things tend to be moved around while the robot sweeper is running so that would put everything out of whack. Of course, if the robot sweeper tends to get hung up in some tight locations, and/or wrestles with electrical cords strung around on the floor, that would also throw everything out of whack. No, this particular robot sweeper does not automatically finish sweeping the floor after it's fully charged.

Yes, if everything is ideal, the Shark RV750N robot sweeper would return to the dock for charging.

As for the battery on the Shark RV750N robot sweeper, it's depleted after the robot sweeps the living room carpet for an hour. What one has to do then is to pick the robot sweeper up, and manually place it on the charging dock.

Check that charging unit to verify that it's actually charging the battery (regardless of the onboard indicators). With my mother's Shark RV750N robot sweeper, the recharging time is around 4 hours. You know, that Shark RV750N robot sweeper has been on the job for several years, and the battery has never been replaced.

Those robot sweepers aren't exactly rocket science so to speak. Actually, I have done all the repairs for the Shark RV750N robot sweeper including replacing the left wheel assembly, cleaning the commutators, and splicing in a wiring harness for the right wheel assembly. Regarding the Shark RV750N robot sweeper's circuit board, I never had to touch it.

As for the disassembly of your robot sweeper, check a youtube video for guidance.

Oh yes, before I forget, some 'conventional tools' may not remove all of those screws so you might have to improvise. Actually, a small flat blade screwdriver might just do the trick. In fact, that was exactly what I had to use in removing some torx screws on my mother's Shark RV750N robot sweeper.

In the photo, one can see the circuit board of the Shark RV750N robot sweeper, and it isn't what I would describe as being necessarily complex. Actually, I had to expose the circuit board at one time in order to splice in a wire harness for the right wheel assembly. As seen on the right side of the photo, the little blue handle flat blade screwdriver was what I had to use to remove some of the (poor quality) torx screws for the Shark RV750N robot sweeper.

Hope this helps!


Attachments:
Shark RV750N Circuit Board.jpg
Shark RV750N Circuit Board.jpg [ 496.4 KiB | Viewed 467 times ]


Last edited by Blustar1 on Aug Sat 06, 2022 1:59 am, edited 2 times in total.
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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 4:12 pm 
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Joined: Sep Thu 30, 2021 6:57 pm
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Location: Keene, NH USA
Alan Voorhees wrote:
The dock voltage is good; tty he contacts are clean. I suppose it could be two bad batteries, but I suspect the charging circuit is defective. I was expecting this to be a fairly easy project, but buying tools isn't that easy here.

All of the Lithium-Ion batteries I have had the occasion to take apart had the BMS (battery management system) built into the battery itself. Most recent was an e-bike battery that wouldn't charge because it thought it was fully charged. In that case, the charger had some simple circuitry in it but not much.


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 5:17 pm 
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Maybe this is the problem??


Attachments:
rosieroomba.jpg
rosieroomba.jpg [ 142.65 KiB | Viewed 438 times ]

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Fri 05, 2022 11:21 pm 
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To keep your tool tips from bottoming out, put a little pebble in the handle's socket as a spacer.

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 2:01 am 
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Sometimes a 1/4" nut driver will work with a hex bit. But there won't be enough clearance if its a typical design.
I have the long shaft Phillips #1 bought for VCR repairs. Don't use it, but I've got it, Be happy to mail it to you.

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 4:40 am 
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Posts: 10083
Location: Baguio City, Philippines
I used Ed's trick and stuffed the shaft with a piece of dense foam rubber and got the last screws out. I had hoped to see signs of a bad cap, but no.
Attachment:
robot_main_board.png
robot_main_board.png [ 840.49 KiB | Viewed 357 times ]


Do I buy another board and hope that's the issue? Or spend the extra $100 and get a new one that I know will work and has a warranty?


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 5:25 am 
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I suspect it's more likely something mechanical to fail?

The second picture is interesting, it thinks it has travelled further north/south than the room actually is?

How much do you know about how it does reckoning? Surely some encoder in the wheels to count distance actually travelled vs requested?

They steer like a tank, right? So any small problem with either drive wheel (in actually turning, or feedback for recognizing it has turned) will completely mangle positioning, i would guess.

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 6:26 am 
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Location: Baguio City, Philippines
The vacuum I have is a Xiaomi G1 "Essential" Robot Vacuum. It is essentially blind, as it has no LiDAR or camera sensors in it, but uses gyroscopes instead. It is interesting to watch it work, as sometimes it just bumps into things; other times it stops just a hare before a collision, then turns away. When it is finished, it will return to the dock to recharge. It doesn't always take what would seem to be the shortest route, so it apparently is referencing the room map it built during cleaning. I would guess there are sensors for measuring in the wheel assemblies, but haven't tried to take them apart. Each wheel has six wires that connect to the main circuit board.


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 11:41 am 
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Alan Voorhees wrote:
...Do I buy another board and hope that's the issue? Or spend the extra $100 and get a new one that I know will work and has a warranty?
I know that $100 is a chunk of change. But I would be inclined to just buy another one and go forward. I don't know if you are inclined to hold on to the old one for parts (or have room for "stuff").

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 1:10 pm 
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Alan Voorhees wrote:
I used Ed's trick and stuffed the shaft with a piece of dense foam rubber and got the last screws out. I had hoped to see signs of a bad cap, but no.
Attachment:
robot_main_board.png


Do I buy another board and hope that's the issue? Or spend the extra $100 and get a new one that I know will work and has a warranty?



No Alan, you do not buy another board unless you know for a fact that it's defective. Anytime that one assumes that something is defective, it costs.

By the way, since you have the circuit board out, it wouldn't hurt to check those larger jacks for cold solder joints, and those smaller plugs for broken wires.


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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sat 06, 2022 3:35 pm 
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Alan Voorhees wrote:
Navigate ii on is through gyroscope sensor. It maps the room every time it runs. That's also why the walls in the map are ragged. It stopped running right on the original battery and with the new one it corrected itself for several days, then got erratic and quit.

The dock voltage is good; tty he contacts are clean. I suppose it could be two bad batteries, but I suspect the charging circuit is defective. I was expecting this to be a fairly easy project, but buying tools isn't that easy here.



What was the actual voltage of the battery immediately after recharging? Could you have attached a couple of small wires to the battery, and monitor the voltage of the battery while it was being recharged?

If the charging circuit on the board itself was indeed defective, there may be an unorthodox way of fixing the problem. Assuming that what you have is a +12VDC battery, this simple trickle charging circuit "might" work, but be sure you isolate this trickle charging circuit from the board. Actually, it might take somewhat longer for that battery to recharge, but what the heck?


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Trickle Charger For +12 VDC Battery.JPG
Trickle Charger For +12 VDC Battery.JPG [ 92.41 KiB | Viewed 295 times ]
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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sun 07, 2022 1:57 am 
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I advise against Lithium recharging that way. Charging regulator boards with CC, CV automatic switchover are very available.
Such as:
"JacobsParts LM2596 36V 5A DC Buck Step Down Voltage Converter Constant Current Power Module"
Search for it on Amazon
They come in many "brand" names, look at the similar listings, too.

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 Post subject: Re: Fixing a Robot Vacuum
PostPosted: Aug Sun 07, 2022 2:08 am 
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My roomba 380t moppy.. batteries lasted about a year from new until they need to be charged all the time and shorten run cycle.

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