Playwithmyled.com

Marvin build with Makeblock, run with a Raspberry Pi that drives an Arduino. Remotely controller by iPhone over WiFi with TouchOSC.

Unboxing Makeblock Configurable 4WD Robot Kit

I can now use TouchOsc on my iPhone to trigger something on my Raspberry Pi. I use the Python library pyOSC to do it. It works practically out of the box. The difficulty was to install the Python library. I’m not so familiar with installing things on linux. For now,  I can send from my iPhone, but today I plan to get it working both ways. I invite you to follow Playwithmyled.com on Twitter to get posted about my progress.

I’m testing the first program for the claw. EDgar can now grab a Lego. The claw sensor is not yet used, but it will be in the next program version. With the sensor, it will spot closing the claw when it will detect an object.

Adding a claw gripper to the robot EDgar.

Replacing EDgar’s wheels. Bigger ones mean faster robot. I stripped the old one. That is the first reason to replace them.

Last week, my son told me he wanted a robot. I took out this old robot from the storage. I never get further than having the motor and a home made H-Bridge fixed to a piece of wood. Back in time, buying a microcontroller was not conceivable.

Too much on a hurry when I choose my Raspberry Pi password, and I wrongly noted it. There is a way to reset the pi user password.

1. Insert the card in your Mac SD card reader (must work on Window too);
2. Edit the file “cmdline.txt” and append “init=/bin/sh” (thanks Joe Schmoe). The Rpi will boot in single user mode;
3. Insert the card in the RPi again and boot up;
4. When prompt available, enter “su” to log as root (with no password);
5. Type “passwd pi” and enter a new password;
6. Remember the new password;
7. Remove the appended string in the “cmdfile.txt” file. Voila!

If you need a password for the root and you don’t have it either, edit the “/etc/shadow” file and replace the root password with a asterisk. Then it will be no password for the root user. (not tested yet).

I finally manage to find a way to make actuators that are enough powerful, small and the most important, noiseless. Since this robot will move all day long, it is essential not to hear it. I tried three types of motors: servos, DCs and steppers. It is not a secret for everyone, theses servos are terribly noisy. The gearbox of miniature DC motor I tried next is too noisy too. At last, I ordered a small stepper with a gearbox and it will be the one selected for the task. So I will replace the three servo motors with these steppers connected to a threaded rod that will move the swash plate.

I’ll have to 3D print some parts to fit all this together, but the essence is there. Now I have to learn to CAD.

There are the two motors, the stepper and the small geared DC one

Testing the small step motor