EEVblog #980 - RoboMaid Automated Vacuum Cleaner Teardown

[EEVblog]

Teardown of the RoboMaid RM-770 Automated Robot Vacuum Cleaner

[Brumby]

Ah......   Wrong link

Fixed!

[WattSekunde]

We use the LG VR64701LVMP working in our rooms. Very good basic every day cleaning! And the LG is relatively silent if you are at home until he works.
They do not replace but reduces the need of manual cleaning!
In our neighborhood there are around 10 dry and wet cleaning bots in use. All from different manufacturers. Nobody want's to miss them any more ;-)

PS: I wish you would power up, measure and analyze more of the parts until the teardowns. That's why I love the always fascinating video #284 on the electrical toothbrush.

[Zbig]

Those main wheels drive motors don't look like steppers to me at all. Just ordinary brushed DC jobs. I don't think they'd be using optical feedback on top of stepper motors in such a cost-conscious device. That's the reason for the worm-gear reduction as well - you wouldn't need that with steppers. Those belts also look toothed, aren't they?

[EEVblog]

PS: I wish you would power up, measure and analyze more of the parts until the teardowns. That's why I love the always fascinating video #284 on the electrical toothbrush.

It's not always possible or worth the time and effort to do so.

[W9GFO]

I don't think the led towers provide any position information beyond a zone to avoid. The robot drives randomly around the room bumping off stuff and staying away from the led towers. When the battery gets low it knows to keep a lookout for the charge base, but it has no idea where it is located. Only when it gets close to it will it see it, then the two leds on the base will guide it in to dock.

[rrinker]

 Whatever you do, don't hook the motor up backwards. Wouldn't want it to go from suck to blow.

[cgroen]

Maybe a coincidence, or not, but seems to be "8 bits" on both LED's....

[TheRevva]

I had a 'robo-maid' type device a couple of decades ago, so perhaps I was a 'trend-setter'? (But I seriously doubt it).
It had some kind of weird artificial intelligence that I never quite understood despite numerous attempts at probing it.
I must admit that it really did SUCK!!!, but It had an annoyingly nasal audible system!
I tried to flash it, but the noise persisted - seemingly getting much worse for about 1/4 of each month?  (I initially suspected some form of lunar linkage)
I ended up completely throwing it out once I became aware that similarly functioning units were available for hire without the negative feedback inherent in my unit.

If my memory serves me right, the make / model was wife-1.0

[mtdoc]

Nice teardown video Dave.

We love our Roomba.

There's an excellent video lecture/teardown by one of the developers of the original Roomba.  He goes into some of the design decisions they grappled with.

[Windfall]

Whatever you do, don't hook the motor up backwards. Wouldn't want it to go from suck to blow.

Only Mega Maid does that. Hail Skroob !



(Okay, I admit it, I watched that movie too many times).

[Windfall]

I have had a Roomba for a few years now. It can't entirely replace the vacuum cleaner, but almost.

What surprised me (as a software engineer) is that it, apparently, doesn't actually know where it is, and essentially follows a random pattern, with a bit of ad-hoc intelligence thrown in here and there. Some other brand (I forget which) does know where it is, maps the area, and tries not to visit the same place twice. Before I bought one, I thought all vacuuming robots did that ! But not Roomba. Also, I think the Roomba's homing is based on radio rather than infrared (but I stand to be corrected).

[Zbig]

I have had a Roomba for a few years now. It can't entirely replace the vacuum cleaner, but almost.

What surprised me (as a software engineer) is that it, apparently, doesn't actually know where it is, and essentially follows a random pattern, with a bit of ad-hoc intelligence thrown in here and there. Some other brand (I forget which) does know where it is, maps the area, and tries not to visit the same place twice. Before I bought one, I thought all vacuuming robots did that ! But not Roomba. Also, I think the Roomba's homing is based on radio rather than infrared (but I stand to be corrected).

Neato uses lidar to map the rooms. Some others (Samsung?) use video cameras to navigate using the view of the ceiling.

[ErikTheNorwegian]

I got two Roomba 615, excelent machinery. Im disabeld, so vacuming is a tonn easier having these robots, they dive under beds and furniture and  do a excelent job. Only need a torrow cleaning with the vacum once every 14 days. Parts, like brushes etc are cheap from E Bay, china sellers.

[ajm8127]

I agree with an above poster that the infrared LEDs are emitting an 8 bit code using pulse length encoding

I wonder how the robot distinguishes the codes from each other in the room where there must be interference between the emitters. I doubt it's as sophisticated as CDMA such as is used in mobile phone air links. I suppose the byte could be arranged such that certain bits are not reused between two emitters so it would know that a particular bit being a 1 or 0 means it must be receiving a unique signal.

For instance if it received 11111100 it would know that it must be seeing both emitters. 11110100 or 11111000 would mean only one emitter it visible.

I guess it uses the different carriers to distinguish between the dock and the "wall". Does it use separate receivers on the bot?

It might be interesting to analyze the circuit a bit more which receives the signals on the robot and see how it connects to the NXP micro. Is it a digital setup that just relies on the threshold between high and low state for the cutoff. Or is it a more sophisticated analog circuit that is sampled by an ADC and then processed on the ARM?

I am guessing this is as simple as possible.

 

[james_s]

I have a couple of 400 series Roombas, they've served me well and I've rebuilt them more times than I can count. The real weak spot on these is the brush deck drive motor gearbox as well as the brush deck itself. The motor area gets full of lint and the motor overheats and melts the gearbox. Other times the gears strip out and iRobot has never offered just the gears or even the whole gearbox as a replacement part. The next issue is that the drive sockets that engage the beater bar and main brush are far too shallow and strip out easily, especially when cat hair gets wound around the end of the brush.

Other failures I've had, the mosfet that controls the brush deck motor burns out, this happens particularly when the motor wears and starts drawing too much current but it can happen on thick carpet as well. I finally got some protected mosfets I'll try the next time this happens. The wires to the front wheel that detect rotation break from the suspension action flexing them. Several times I've had IR LEDs in the drive wheel tachometers get weak, same happened once to one of the cliff sensor LEDs. Brush deck and vacuum motor bearing failure, clay based kitty litter is especially hard on these, I found suitable replacement motors from Jameco IIRC. Speakers have failed on both of mine, I replaced them with small paper cone speakers, they sound better too, not that it matters. Side brush gearbox gets hair wound around the shaft and eventually has to be taken apart for cleaning.

In a nutshell, I'd have a hard time recommending one to someone who was not technical because they are maintenance intensive, unless you have so much money that you can buy a new one when it breaks, in which case you should just hire a human maid. Personally I'd much rather tinker with robots than vacuum the house though, and the Roombas significantly reduce the frequency I have to do a proper manual vacuuming.

[HwAoRrDk]

(Okay, I admit it, I watched that movie too many times).

Don't let Dave catch on to it, he might start getting some funny ideas about EEVblog merchandising.

"EEVblog the T-shirt! EEVblog the colouring book! EEVblog the lunch box! EEVblog the breakfast cereal! EEVblog the flame thrower! Last but not least, EEVblog the doll - me, Dave Jones. <pulls string> 'I'm innnn like Flynn'"

[mtdoc]

have a hard time recommending one to someone who was not technical because they are maintenance intensive

We've had exactly the opposite experience with our Roomba 595.  I was skeptical about these but my sister in law raved about theirs (and she and my brother have no mechanical skills) so I got one several years ago and it has been great. We have a large dog with long fur and despite this, we have not needed to do any maintenance other than cleaning out the rollers, etc. It just keeps trucking along. We have it set to run automatically 3x a week and then use it manually probably once a week as well. It's been going for about 3-4 years like that with no issues. I keep expecting to need to get a new battery but so far it's still doing fine.

[james_s]

Perhaps they've made improvements. My mom has a 500 series and it has been marginally more reliable than my 400s but even so I've had to replace the complete brush deck once. I also had to disable the cliff sensors by removing the sensors and relocating them inside because it kept getting confused on the bamboo hardwood flooring and thinking it was going over an edge. She has a single floor house so they're not necessary anyway. I also am at a bit of a loss as to why the computer portion in the 500 is so powerful, it's a big ARM chip IIRC, even plays verbal messages, seems overly complex for what it does and the things are obscenely expensive given the plastic gears and toy-like construction.

None of the competing robotic vacuums are nearly as good despite the flaws though.

[Zbig]

None of the competing robotic vacuums are nearly as good despite the flaws though.

Have you tried Neato?

[madires]

Maybe a coincidence, or not, but seems to be "8 bits" on both LED's....

The virtual wall has the same protocol. My guess is that the first two pulses are the start bits, the short pulses are 0 and the long pulses are 1 (about 4 times the short pulse). Nothing fancy.

[rrinker]

(Okay, I admit it, I watched that movie too many times).

Don't let Dave catch on to it, he might start getting some funny ideas about EEVblog merchandising.

"EEVblog the T-shirt! EEVblog the colouring book! EEVblog the lunch box! EEVblog the breakfast cereal! EEVblog the flame thrower! Last but not least, EEVblog the doll - me, Dave Jones. <pulls string> 'I'm innnn like Flynn'"

 
We're not doing this for the money. We're doing it for a shitload of money!

The sad thing is, if there really were a Dave doll that said some of Dave's catchphrases, I'd probably buy it. The modified See 'n Say was too damn funny.

[james_s]

I'd consider buying the EEVblog flamethrower.

[rrinker]

 If you think Dave has problems shipping multimeters around the world.... 

[ErikTheNorwegian]

What?
A  EEVBlog branded  scope?   

 

[Windfall]

"EEVBlog : the oscilloscope !" 

[Brumby]

What?
A  EEVBlog branded  scope?   

You don't remember last year's Scope Month, do you?

[Brumby]

Dave's announcement of the 2016 Scopemonth promotion - (LAST year's)

https://www.youtube.com/watch?v=6xaSYi_n6fw#t=2m17s

I do love that dumpster ... !

[Brumby]

Here's a shot of the front panel, showing the power on splash screen...

[james_s]

Does it make snarky remarks if you try to do something it doesn't like?

[Brumby]

Not that I know of.

It just has Dave's trademark graphic to do that.

[Windfall]

Not that I know of.

It just has Dave's trademark graphic to do that.

It's a rather unfortunate logo isn't it. It looks like Dave trying to warn you against using this scope !

[Twoflower]

The downlooking IR-sender/receiver combo is to prevent to fall down stairs. At least the Rooma has some trouble with it there are reports that they not work 100% (dust?) and it also prevents to use them on very dark tiles/carpets (cover with white paper solves this, but it makes the Roomba blind for stairs).

The UV is probably meant to desinfect the floor. How useful it is? I don't know. Probably marketing.

For the Roomba the base station sends two different beams for left and right to identify the alignment between base-station and vacuum. The Top-signal is (again for Roomba) used to prevent the Roomba hitting the base-station.

I think the piezos are only used as impact detector. If dirt is detected it changes the cleaning mode.

Below is a picture of a Roomba in action with a old** NightVision (no IR filter) capable Sony video cam. In IR it makes a nice light-show.

** Yes it uses tape, and the good old PAL resolution

[Brumby]

Not that I know of.

It just has Dave's trademark graphic to do that.

It's a rather unfortunate logo isn't it. It looks like Dave trying to warn you against using this scope !

Not against using the scope - just the reaction you'd get when about to clip the ground lead of the probe to somewhere you shouldn't.

Maybe that's why they put that graphic down near the input sockets.....

[Alexei.Polkhanov]

Cold cathode UV lamp to kill bacteria in dust collector?

[thm_w]

Cold cathode UV lamp to kill bacteria in dust collector?

https://en.wikipedia.org/wiki/Ultraviolet_germicidal_irradiation

Yes to kill bacteria, no not in the dust collector as it was pointing down towards the floor.
The cover is likely plastic as well (best case glass) which will block a decent percentage of that UVC. As others have stated, its essentially a gimmick.

[james_s]

I doubt it would spend enough time over any given area to kill a significant amount of bacteria, and if it did, it would fade the carpet.

[bitwelder]

Generally how long would it take for a UV lamp to kill bacteria? I guess more than a few seconds.
Considering the location of the lamp on the RoboMaid it would 'disinfect' the floor one poststamp-sized tile at a time. It doesn't look much practical to me.

[Paul Moir]

It depends on the exposure strength mostly.  It's pretty much a linear relationship with most microbes.  The other thing is how many microbes you want to kill.  1 second might get you 1 log reduction, then 2 seconds gets you 2, etc, so a log relationship on that.
And of course it depends on the microbe:  some are pretty hardy while others are wimps.  That all said, I can't imagine this would work very well on carpet where I expect most the microbes would be hiding down inside and well protected from the UV.
EDIT:  I don't think that really answers you question.  Lets just say that to kill almost all of a fairly average nasty you'll need exposure from a 253nm UV source to the point where you're you're going to get skin irritation.  This little bulb may actually kill the occasional bug but it's not going be sterilizing anything.

[SeanB]

There to find the nose candy you dropped, so you can grab it out of the dust collector. Will also work to annoy any bacteria on the carpet.

[Domagoj T]

What's the deal with the wheel drive? It's a rather complicated system, having stepper motors and drivers, optical encoders, logic for both and then the belt and worm gear.

While, generally speaking, I like stepper motors and their simple control logic, once you introduce optical encoders you can easily use regular DC motors which are cheaper, produce less noise, require simpler electronics and are more energy efficient (something that is usually an interesting aspect in a battery operated device).

Now I'm thinking of going to flea markets and salvage some Roombas for their motors.

[Zbig]

What's the deal with the wheel drive? It's a rather complicated system, having stepper motors and drivers, optical encoders, logic for both and then the belt and worm gear.

While, generally speaking, I like stepper motors and their simple control logic, once you introduce optical encoders you can easily use regular DC motors which are cheaper, produce less noise, require simpler electronics and are more energy efficient (something that is usually an interesting aspect in a battery operated device).

Now I'm thinking of going to flea markets and salvage some Roombas for their motors.

Do you read threads also or only reply? I commented on that in the 4th or so post. Dave's not that big on (electro)mechanics and sometimes makes mistakes like that.

[Domagoj T]

Do you read threads also or only reply? I commented on that in the 4th or so post. Dave's not that big on (electro)mechanics and sometimes makes mistakes like that.

My bad. Not sure if it's an excuse, explanation or an even bigger hole I'm digging for myself, but I did read you comment a few days ago, it's just that I occasionally take my time to jump in the conversation.
In any case, I've rewatched the segment with the motor and it really is just a regular DC thingy. A PCB on the motor and a bunch of wires leading to it, combined with Dave's mistake contributed to my own perception that it is a stepper, so I didn't give your post the credit it deserved. My apologies.

Also, for the last couple of weeks I've been working on several different stepper applications of my own, so I'm starting to see them everywhere.

[Zbig]

No need to apologize, my comment was a bit too harsh Peace!

[ErikTheNorwegian]

From:

"http://tothotornot.com/2013/08/hot-robomaid-robot-vacuum-cleaner/

An unexpected feature that I discovered when I first turned on the Robomaid was a little blue light and ‘UV’ on the display screen. Turns out that the machine includes an in-built UV light which apparently kills bacteria, germs, dustmites and microscopic insects as it vacuums. I have no scientific data to back up whether this in fact occurs but I figure it can’t hurt, especially as Tim suffers from hayfever and my nose is pretty sensitive to dust."

The UV light seems to killed the company to..

http://www.commerce.wa.gov.au/announcements/consumer-advice-buyers-robomaid-vacuum-cleaners

"Consumer Protection has issued advice to WA consumers who have ordered a Robomaid automatic vacuum cleaner and are yet to receive it, to claim a chargeback from their credit card provider or PayPal.

Robomaid Australia, the company which has been importing the product from China, has ceased to trade but has not yet appointed a receiver or liquidator."

[Nobody2]

The downlooking IR-sender/receiver combo is to prevent to fall down stairs.

Oh that would make sense. When I first saw them I thought they might be motion detectors (working like a simple mouse sensors), but a stairs detector sounds much more likely.

[james_s]

The downlooking IR-sender/receiver combo is to prevent to fall down stairs.

Oh that would make sense. When I first saw them I thought they might be motion detectors (working like a simple mouse sensors), but a stairs detector sounds much more likely.

The proper term is "cliff sensors", that is precisely what they're used for. When the Roomba approaches an edge, it immediately stops, backs up and turns.

[Zbig]

Oh that would make sense. When I first saw them I thought they might be motion detectors (working like a simple mouse sensors), but a stairs detector sounds much more likely.

Don't get mislead by their (mouse sensors, that is) low price and ubiquity - there's nothing simple about them. What they really are is tiny integrated machine vision systems with video cameras taking detailed high-FPS footage of the surface and DSPs comparing each subsequent frame to the previous one and calculating the speed and offset in real-time. Compared to that, simple reflective IR sensor that either sees a floor below it or doesn't is a walk in the park.

[Domagoj T]

(mouse sensors, that is) low price and ubiquity - there's nothing simple about them. What they really are is tiny integrated machine vision systems with video cameras taking detailed high-FPS footage of the surface and DSPs comparing each subsequent frame to the previous one and calculating the speed and offset in real-time. Compared to that, simple reflective IR sensor that either sees a floor below it or doesn't is a walk in the park.

They really are marvelous things, and to think that you can get one shipped from China to your doorstep for less than $2.

*Some microswitches, optical sensors on scrollwheel and a few feet of cable included.
** Optional wireless connectivity for minimal additional cost (batteries not included).

Mind-boggling.

[brucehoult]

I bought one of the first Romba back in I guess 2006 or 2007. They're pretty awesome. You think you've done a good job of vacuuming until you see how much crap the Roomba picks up after! And possibly the other way around too .. they're somewhat complementary devices.

Navigationally they're very stupid. It's mostly a drunk walk around your house, just with a few different behavioural patterns that it follows for a more or less random time (a few seconds up to maybe 30 seconds) each e.g. "follow walls on the right side", "make 80 degree (or 100 degree) left turns when you hit something", "make right turns when you hit something","make a nearly 180 degree turn displaced by one Roomba-width when you hit something after a long (~5m?) straight run without hitting anything". It ends up over the course of an hour or so being pretty effective at discovering every room and covering every spot in at least a 50 - 80 m^2 level of a house or apartment.

Sadly, that machine is back in NZ and I've been cleaning manually in Moscow. Sadly the air here is very dusty and you need to clean hard floors every day, or two at the most, to avoid a gritty feeling underfoot and black soles of your feet when you go to put your shoes and socks on.

I guess this thread inspired me to notice a Roomba in the window of an icover.ru store as I was walking around near (but not tooo near) the protests yesterday and I picked up a Romba 681. The 616 was a bit cheaper (19900 rubles, AU$450, NZ$500) but for an extra AU$135/NZ$145 the 861 comes with a higher capacity LiOn battery instead of NiMH, and a few included accessories such as a virtual wall and spare filter and side-brush. Other than the battery those things are pretty cheap as spare parts anyway.

The thing is overall very much the same as my original model, but you can see small improvements everywhere. The most immediately noticeable difference is it now somehow slows down a lot about 10 cm before crashing into walls and furniture. The original just crashed into things at full speed. The new one gives a very gentle almost inaudible nudge. I don't know what sensor they're using for that. I'm guessing ultrasonic, but I haven't spotted a transducer. It's not sensitive enough to notice thin chair legs or the ends of panels on flat pack desks, and still hits those at full speed.

There's now a 900 series of Roombas for about twice the price with WIFI and remote and smartphone apps and apparently real mapping of your house using a camera and proper planning of efficient cleaning patterns. Meh. The cheap one works fine.

[bitwelder]

There's now a 900 series of Roombas for about twice the price with WIFI and remote and smartphone apps and apparently real mapping of your house using a camera and proper planning of efficient cleaning patterns. Meh. The cheap one works fine.

Burglars with a cyber streak cannot wait for anything better. 

[james_s]

Yeah I don't see any real reason for that. I've run one of the old Roombas in a room that had carpet where it left a visible track of where it had run, and by the time it finished you could see that it had crisscrossed everywhere and not missed anything. Where they have trouble is when someone keeps interfering with it trying to get it to go to a specific area, just let it run, it will cover the whole room.