Monthly Archives: October 2012

Change Raspberry Pi lost password

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).

Noiseless actuators

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

Small step motor and miniature geared DC motor

Testing the small step motor

Testing the small geared step motor