Tiny black brush under i7/i7+?

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Tiny black brush under i7/i7+?

Postby bytemaster0 » October 15th, 2018, 3:52 pm

Hello all,

I'm trying to figure out what the teeny tiny black brush is on the underside of the i7/i7+. It's located near one of the cliff sensors, and right next to one of the screws. Photo here (or attached): https://photos.app.goo.gl/cdUyBaXq9RL7ZjB4A

A couple of thoughts:
1. It's a pile height sensor - it gets "tickled" by higher carpet, causing some sort of change in navigation, power, or something else. Wondering if there's a strain gauge or something else behind it. Note that taking the cover off the bottom doesn't expose it!
2. A static discharge method. Seems unlikely.

I yanked on it pretty hard earlier by accident, thinking it was some caught hair. It's not. If it's a sensitive sensor, I'm worried that I might have caused damage. Roomba support has no idea what it is, and one rep even dismissed it as cosmetic. This is a mass-manufactured robot. Nothing is cosmetic, and no sensor or other part would be added just for kicks. Any ideas? I don't feel like dismantling the thing completely.
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Last edited by bytemaster0 on October 15th, 2018, 8:49 pm, edited 1 time in total.
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Re: Tiny black brush under i7/i7+?

Postby Dfm1011 » October 15th, 2018, 4:25 pm

There are so many weird things about the i7 that I don't understand!

1) Where is the fricken exhaust vent?! It's not like the air just disappears! It must come out somewhere. I'm suspecting the air is protruding from the rims of the grey faceplate of the robot.

2) (See the attached photograph) What the heck is that large bump? It's on every single Roomba. Perhaps it's meant to raise the carpet fibers to make them look "groomed".

3) Like you pointed out, what the heck does that brush do?
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Re: Tiny black brush under i7/i7+?

Postby ps0001 » October 15th, 2018, 10:46 pm

I've been wondering what that brush is for too. Vic has taken his i7 apart already, maybe he can shed some light on it.
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Re: Tiny black brush under i7/i7+?

Postby bytemaster0 » October 16th, 2018, 12:32 am

Yes, I hope so! Not enough time on the schedule for a full teardown for me. Can anyone who has done a teardown figure out if there are any wires coming out from that piece? Or, more specifically, more than ONE wire? One wire might point to a grounding system. More than one means it's a sensor of some kind.
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Re: Tiny black brush under i7/i7+?

Postby vic7767 » October 16th, 2018, 9:41 am

ps0001 wrote:I've been wondering what that brush is for too. Vic has taken his i7 apart already, maybe he can shed some light on it.


I do remember seeing that mini brush during disassembly. Problem being other interests about CPU power and part numbers took priority. Of course the i7 is now back together but will get taken apart soon in search of an answer to this small device.

The main difficulty now is there does not seem to be any on board diagnostics or ascii output port that would possibly identify the brush style sensor.
Roomba and Neato Mods, come visit: http://www.vic7767.com/
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Re: Tiny black brush under i7/i7+?

Postby bytemaster0 » October 16th, 2018, 3:55 pm

Vic, thanks for your reply! If you do find it, I'd love to know what it is! I noticed in another pic that it is indeed connected by one big red wire. I wonder if it's measuring the accumulation of electrostatic charge to assess pile height or something like that. It can't be a full-fledged sensor though, as that would require power/ground/data, or at least power/ground or rx/ground wires. As it's a big honking red wire, I wouldn't attribute it to a simple ground wire, though I guess they could have ignored color convention. However, I now that I know it only has one wire, I guess I probably didn't really damage anything. Still super curious about its structure and what it's supposed to do. Roomba support is supposed to call me back about it in a few days, including about a frankenmap that my i7+ is creating. Thanks for your reply!
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Re: Tiny black brush under i7/i7+?

Postby bytemaster0 » October 17th, 2018, 12:41 pm

Guys, I received an answer directly from iRobot. Per their reply:

"That brush is there to help the robot dissipate static charge that may build up on the robot on certain types of flooring or environmental conditions. It does not exactly play a huge role in Roomba's cleaning performance but it does help with various floor types."

So, mystery solved! Looks like it was indeed one of the two original hypotheses. Thanks all for your participation!
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Re: Tiny black brush under i7/i7+?

Postby ps0001 » October 17th, 2018, 2:11 pm

bytemaster0 wrote:Guys, I received an answer directly from iRobot. Per their reply:

"That brush is there to help the robot dissipate static charge that may build up on the robot on certain types of flooring or environmental conditions. It does not exactly play a huge role in Roomba's cleaning performance but it does help with various floor types."

So, mystery solved! Looks like it was indeed one of the two original hypotheses. Thanks all for your participation!

Good job! Considering you found there's only one wire, that explanation makes a lot of sense.
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Re: Tiny black brush under i7/i7+?

Postby vic7767 » October 17th, 2018, 2:29 pm

bytemaster0 wrote: mystery solved! Looks like it was indeed one of the two original hypotheses. Thanks all for your participation!
:cheers:
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