Let's Make Robots!

Robot with Tracks

Hello, just a question to all who made a robot with the tamiya track set: did you implemented any kind of track tensioner? or just calculated the size and "stretch" it over the sprokets&wheels ?

Arduino and I2C LCD

(cross posting with arduino forum.. no answers there :(( )

Problems with i2c (and an LCD display)

So, i just wasted an evening trying to make an LCD with i2c work with my picaxe.

I connected the SCL and SDA of the board to the other end on the LCD. (of course not crossing them :P)  BTW on the picaxe the pins are: Digital input 3 = SCL; Digital input 4 = SDA, am i right ?

If so, other question is: do i need the two pullup resistors ? i've read somewhere that they're already there on the board. But if so, the pin should be high most of the time, shouldn't it ? testing with my voltmeter reads 0V. 

PS i have the picaxe 28x1. 

DIY laser cutter

Reading about all those lucky people that have access to a laser cutter, i was wondering: can we make one? I mean, build a custom (cheap) laser cutter?

I think it should be something like a plotter, so with a couple of fine-grained steppers and a frame structure (maybe some old scanner) that should be ok.

The problem is the cutting :P where can one find a good laser? i thought about CD-Writer but they have about 100 mW.. I don't know, maybe it's enought for a small dark acrylic sheet.. But i think the optical stuff won't fit :)

Questions about Sparkfun shipping

Hello, i'd like to buy some stuff from sparkfun.. The question is: do they ship to Italy? I searched the site but they don't tell which countries are supported and which not. Also, what shipping method should i use? There's a cheap $20 or such but i guess it's only for US (right?) or a quite expensive (about $60) fedex shipping.

Also, how does the prices get converted to euro? Are there some extra costs?

Battery chargers

Hello,  just to know what kind of battery chargers do you use ? any advice on what to buy ?

Encoders, what are they ?

So what is the difference between a motor with an encoder and one without?

i think it kinds of read how much the motor is rotating, but can't i see that from how much current i'm giving? what are the uses for these encoders?

The infamous Kalman Filter :)

So maybe any of you heard about it, but is there anyone who have made a working implementation?

Or eventually a nice site with a human readable explanation :) ?

Useful robots

Hello :)

I have this question: has any of you ever built a useful robot, that is, a robot with some real task that helps you, instead of just making it for fun ?

The other day a friend of mine was complaining about the time it costs him to cut the grass, and told me jokingly he could use a nice autonomous robotic lawn mower. I thougth that it could be a task within our building abilities.

What other useful robot could be realistically done?

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What about changing that default Drupal favicon to something custom ? :)