Let's Make Robots!

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. 

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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 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 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. 

How do I connect a 5V sensor to a 3.3V input

Hi

I am using a IR sensor (photo transistor) that was ripped out of a ball mouse and I am running it at 5V, but I need to connect it to a Raspberry Pi which runs at 3.3V (at least the IO-pins are). 

I can place a 3.3V regulator before the sensor and adjust the pull down resistors, or use a zener diode to limit the output, but I was wondering wheter my currecnt setup will be safe to use.

Sorry for the poor quality drawing by the way.

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.

Relay vs H-bridge question

most of the time I use an L298D motor driver IC for controling motors. However i find that the 1+ voltage drop is anoying. Some motors just dont go fast enough. 

Using a 7.2V power supply, leaves about 6V going to the motors and, as I understand it, the L298D is not designed to take in higher voltages. Although I think it can handle quite a bit if you cool it properly.