Saturday, April 26, 2008

Roomba 570 scratch protection

I wish iRobot would build the sides of their robots with more scratch resistance plastic or rubber. The plastic they use may be cheaper but a robot that runs into furniture to find its way around the room really needs better protection.

I protect my iPod and digital camera with plastic film sold by bestskinsever, invisibleshield and others. The film is basically the same as 3M Scotchguard. It is less than 1mm thick and is highly resistant to scratches. It is aparently the same film used to protect helecopter blades from damage. I haven't read about anyone else using these for protecting roombas but I think it's an ideal solution. The protective film is cheap, thin (does not change the appearance of the roomba), slightly soft (protects furniture from bumps) and easy to install (only requires soapy water to activate the stickiness). The film is highly adhesive (does not come off by itself) but is actually easy to peel off and leaves no visible marks or residue behind.

I bought some A4 sheets from bestskinsever and cut them to the right shape to protect all around the sides of the roomba and around edges on the underside of the roomba. The flim performs perfectly. After 3 weeks of use, the roomba still looks brand new with no visible scratches on the sides and all my furniture remains undamaged.

Manually cutting the plastic film to shape is time consuming but installing the film is much easier to install on the roomba then an iPod LCD because you don't need to be overly careful with dust particles and optical clarity.

Here's some pictures of the protected roomba 3 weeks after the protective film was installed:

A shot of the front right of the roomba. There's two strips of film in this photo. One over the right hand sensor bar and one over the plastic under the sensor bar. Cutting the strips for the sensor bar was the most difficult because of the round edge at one end of the sensor bar (far left in the photo).

A close shot of the end of the roomba's left sensor bar. You can see that the sensor bar and the plastic surrounding it are covered with seperate strips of plastic film. The protective film gives reflections a slight "orange peel" looking effect.

It's a bit difficult to see but there are panels of plastic film protecting the back of the roomba too.

Here's a close up of a couple of plastic film panels protecting the side of the roomba.

Here's a close up shot of the front center of the roomba showing the two protected sensor bars.

Wednesday, April 16, 2008

Adding metal bearings to the Roomba 500/Roomba 570 Gear Box

Before buying my Roomba 570, I was aware that the Roomba 500 series had a design flaw that causes the gear box to fill with dust and hear which would eventually cause it to malfunction. This video on YouTube by another Roomba owner details the problem.

I was hoping that iRobot would have already resolved the issue by the time I got my Roomba. After running my Roomba for a week, I opened the gear box casing to find it full of fluff and cat hair. The dust and hair enters through rather large gaps between the roller/brush driver cogs and the hole in the gear box casing they protude out of.

I found this post by vic7767 from RoombaReview. vic7767 uses ball bearings to allow the driver cogs to protude from the gear box casing whilst keeping the gear box casing sealed (no gaps around the edges).

The sizings of the ball bearings are pretty standard and I found a local supplier of bearings that had all three sizes necessary in stock. The sizes (Dxdxw) are 23x17x4mm, 10x15x4mm and 6x10x3mm.

Here's some pictures of my mods:

Medium sized driver cog with the bearing mounted. The cog had to be filed down a bit to fit the bearing.

The large driver. This had to be filed down several millimetres too.

The large driver cog and the bearing next to it.

The smaller driver cog in place. The hole in the cog assembly had to be widened with a file.

The opening on the left is what things are like without bearings. Even with the driver cog inserted, the opening left plenty of room for dust and hair to get pulled in.

Both driver cogs with bearings fitted.

The cogs fitted in the cog assembly with the bearings. No more gaps for dust to get in. Nice.

The smallest driver cog (mates with the motor shaft) along with its matching bearing.

The smaller cog fitted onto the cog assembly. Slow and careful filing gave the cog a nice tight fit.

The cog assembly from the inside with all cogs fitted.

The fitted cogs and bearings again.

Roomba on his back with the back cover off.

The driver cogs with the brush and beater fitted.

Friday, April 11, 2008

Fixing/Converting Roomba adapter from 110V to 240V for New Zealand

I recently bought a Roomba 570 robotic vacuum from ebay. The robot came with a 110V/120V adapter. Since I'm pretty used to seeing adapters that support 110V-240V, I didn't bother checking the ratings and was greeted by an alarming bang and puff of yellow smoke when the adapter was plugged into our New Zealand 240V mains.

Fixing & Converting the switch-mode adapter from 110V to 240V is relatively easy but you shouldn't attempt it unless you know what you're doing. It can be very dangerous whenever working with high-voltage devices.

Opening the white adapter casing up was relatively easy (the screws are underneath the rubber feet). The yellow smoke came from a blown 200V 47uF capacitor.

To convert the adapter to 240V, you need to replace the 47uF capacitor with a higher voltage capacitor but similar capacity capacitor. I was able to get a 450V 47uF capacitor from jarcar for under $8. I would have preferred to get a capacitor with a lower voltage rating but couldn't find any local suppliers. Because of its high voltage rating, the 450V capacitor was a bit too large to mount vertically so I had to mount it sideways. I secured the capacitor from contact with other components using some blobs of hot glue. Electrolytic capacitors are polarised so make sure you make a note of which way round the original capacitor was mounted when you mount the new one.

The only other component you need to change is the varistor which is the blue disk-like component. The varistor protects the circuit from high voltage spikes. I used this one from jarcar which was under $2.

When you've finished putting the adapter back together again, plug it in and carefully measure the DC output from the circular plug (the one that goes into the docking station). The adapter should be outputting 22.5V. You shouldn't plug the adapter into the Roomba docking station until you are sure that the adapter is properly outputting 22.5V otherwise you could damage the docking station and the Roomba if it's docked.

Now for the pictures:

The adapter after it has been opened. The capacitor (top) and varistor (bottom left) have been circled. Notice how the capacitor has burst.

The replacement components. A 47F 450V electrolytic capacitor and a 275V varistor.

The original capacitor (left) and the replacement capacitor (right).

The adapter with new capacitor and varistor in place.

The adapter lid would not close because the 450V capacitor was too large. Here, the capacitor is mounted sideways.

The Roomba, happily charging from his newly converted 240V adapter.