Let's Make Robots!

mintvelt's blog

I2C IO expander/servo controller using a picaxe 20x2

20x2 picaxeI needed analog ports and servo control for the RPi in my R2D2 project that can be controlled with I2C. Because I have a few spare Picaxe ICs I decided to make one using a Picaxe 20X2. Currently I only need a single servo and a single analog input, but I don’t want to reprogram the Picaxe every time I add another sensor so I wrote the attached code to turn the 20X2 into a general purpose IO expander. 

R2D2 Third Leg

Started to work on the third leg today. Inside the body four aluminium pipes guide the platform where the third leg will be attached to. The platform needs more stability going up and down, so extra gliding holes will be placed somewhat higher around each pipe in order to make sure the platform stays horizontal when moved.

R2D2 feet

just a quick update on my mini R2D2 project.

I am making some progress, but slowly, very slowly. There a just so many choices to make that sometimes I can go for weeks just thinking up solutions for all the bits and pieces of this robot without actually building anything. Thats why I started trying a few ideas to get R2D2 moving.

Mind the Raspberry Pi power usage

The RaspberryPi is a powerfull little gadget that can add a lot of good features to your robot. For under $60, including cables, dongle and SD-card, you get a lot of processing power, data storage, wifi and audio. So I ordered a RaspberryPi to be used as the brain for my R2D2 project.

Electric IMP : Easy Wifi

The Card

I was looking for a simple way to add Wifi to a robot project, when someone pointed me to Electric IMP. After reading a little about it, i decided to just order one and try it out. A few evenings of toying and I have to conclude that the IMP is a whole new type of component.

R2D2 Body

This part of my mini R2D2 project. i'll post all the updates on the main body in this blog page.

This is the first bit of frame with some extra bits. Those pieces are for two doors: one large one that covers allmost the whole back and a small one in the front.

R2D2 Legs

This page is part of my mini r2d2 project and this is where I keep track of my progress on it's Legs.

I only just got started on them and allready I realise there will be lots and lots of sanding to be done. The legs are very thick so I need to glue several pieces together.

R2D2 dome

This is part of my mini-R2D2 project. I intend to keep blog pages for the different parts of the building process. 

The dome is made out of a clear plastic sphere. I found 2 globes 16cm in diameter and 2 smaller ones 4cm across.

First step. Dremel off the bit that is sticking out and sand the whole thing. 

Arms for Edward

After lots of thinking about what my next robot should look like, I couldn't resist the temptation of trying to improve Edward. I never really made a good program for him and everybody who sees him ask me to switch him on and let him run around. When they do, i shrug and tell them "the batteries are dead" or "I'm still working on the programming".

PicAxe 20X2 mainboard

This is the second board I received from sparkfun / batchPCB. The other one, a motor driver, is tested and done.

08M motordriver and power supply board


After a few weeks of waiting, my PCBs have arrived. I just soldered the components on the first one and it works like a charm. I had to drill out the holes for the resistors a bit and then solder the resistors on both sides of the board to get a good connection, but hey: this was also my first shot at having a PCB made and it works. Next time I'll be more careful checking out the dimensions in diptrace.

Edwards circuit board

I got some questions from Adobi123 on the design of the board I built for Edward. I dont have any schematics cause it was done on the fly by laying the components on the board and trying out which locations would fit best. Anyway; I made a description of the components I used and I'll link some of them to relevant pages with documentation.

The board


This will eventually become a robot project, but because my progress is so very slow, I decided to post the bits and pieces I have as a blog. That way you guys can start commenting and I get to show my pretty pictures.

The bot I'm working on will combine some of the things I allready posted as walkthroughs. Mainly it will feature the mintvelt object tracker and inter-picaxe serial communication.

Smooth Object Tracking (has been moved)

I was looking for a way to have a robots head follow something or someone around. I've seen some robots that have a servo with an IR-sensor on top that finds either the left or the right edge of anything you put in front of it. I toyed around with that, but I got frustrated with a few things.

If you follow the left edge of an object, the robot allways seem to look slightly left past the object instead of in the middle. Also:When the edge is detected, the servo goes from left to right and back between detecting the object and looking past it.