My wife got a Roomba 650 for Christmas, and one of its first tasks was to vacuum the dining room. In our dining room is a small carpet in front of the door (little brother to the bigger ones in our living room and foyer), with a wonderful variety of geometric patterns on it. Patterns that caused the poor little 'bot to totally spaz.
Looking around on the Interwebs, I found this forum, and this thread (huzzah! Love this forum!!) And while the concept espoused here made perfect sense to me in general terms, the engineer in me was not satisfied with the solution as it was presented. So I set out to craft, what I think, is a better solution.
But first, why it didn't make sense to me. The cliff sensors each are made up of a pair of infrared (IR) transmitters (phototransistor) and receivers (photodiode), and that pair is separated by an opaque plastic "wall" between the 2 of them; look closely at your 'bot and you can see it running right down the middle, and extending just a tad (technical term) above the transparent window. Putting a piece of paper or aluminum foil over the window would do nothing
to channel the IR light between the 2 sides; in fact, it would be more
prone to block it. I'll speculate that the aluminum foil that worked for folks was loose and crinkly, with lots of little channels between the 2 sides. The calls for "high quality white paper" leads me to think that people were using thicker fiber stock, that gave the IR light plenty of room to channel through
the paper, between the 2 sides of the sensor's chambers.
So, let's take a look at the IR light. My wife's phone just happens to have an IR mode, so here is the light being emitted from the transmitter:
What I figured we'd need was a "channel" of some sort, that would funnel the light from the transmitter's side to the receiver's side. So I tried a couple different pieces of straw to see which reflected the light best, and settled on this one:
What is it? It's the hard plastic straw from a water bottle. This particular one's made by CamelBak, and you can buy spare straws at various sporting good stores (I've bought mine at Dick's and Mountain High).
And it turns out, after trimming one to fit my bottle, I had just enough left over to be used for this task!
I cut this piece into 2 pieces, each about an inch long.
Then, I proceeded to cut them in half. After cutting off the tip of my left index finger by using a Really Sharp kitchen knife
(I'll spare you the picture of blood all over the kitchen), I then got out my metal shears and cut them down one side:
then used the Really Sharp knife
to cut the other side:
I now had 4 pieces of "IR channel" to apply to the 'bot's sensors.
I put a piece of scotch tape on each, with about ½" of overhang on one side, and ¾" on the other. The shorter piece went on the inside of the sensor, the longer side went on the outside.
Et voilá, the final result…
- Make sure the tape is secure; I've already had one IR channel fall off because I didn't firmly press the tape down, and have a second about to come off too.
- If you use a different material, find a camera that will help you determine if the material is reflective in the infrared. Just because a material is opaque to your eye does not mean it won't be transparent to IR.
- Be careful using sharp knives. No, really!
I'm toying with the idea of supergluing these pieces in place; since they're open-ended channels, I can easily use a can of air to blow out any accumulated dust within.
Hope my adventure helps someone! Even if it's just to remind people to be safe when playing with knives!