Showing posts from August, 2010

Shrediquette with IMU 6DOF Razor - Ultra-Thin IMU

Sven - a friend of mine - built his Shrediquette using the cheap IMU 6DOF Razor - Ultra-Thin IMU. Some modifications have to be done, because the gyros and accelerometers on this IMU work with 3.3V instead of 5V:

You will also need to modify the source code, because the arduino needs an external 3.3V reference for the ADC. Modify this line to change from AVCC to AREF:

Config Adc = Single , Prescaler = Auto , Reference = Aref   'reference is changed from AVCC to external reference AREF

The source code for an external reference:

Here is a video of Sven's Shrediquette. I also had the opportunity to test it in flight, and it flies really good.

The only drawback is the IMU's sensitivity to vibration, so you really have to make sure that vibrations are generally low. This is how Sven tried to dampen the IMU:
If you have questions regarding this mod, please contact Sven (email is in the pictures above).

Firmware improvements

Gyro offset measurement changed. Right after the startup, the copter tries to measure the gyro offset. If the copter is moved during this period, it won't continue with the start-up. Instead, it will flash the LED in the middle until the copter is placed on the ground. Only then it will initialize.Servo control improved: The servo pulse generation is now synchronized to reading out the receiver. Additionally, it is not possible anymore that an interrupt makes the servo jitter (thx to Lutz Meyer). All servos should work much better now.

FPV videos, firmware tweak, user builds

Some days ago, I added two FPV videos to the video-section:

There are also some more details on the FPV setup that I use in the FPV section. Additionally, there is a new section showing some Shrediquette user builds. Please keep on sending me details about your own build.
Soon (next days) I will release a firmware update, that seems to reduce servo jitter, especially when using fast digital servos. Lutz Meyer tweaked some lines of the source code (thanks! :-D ). Lastly, for all people from northern germany, I would like to point your attention to a quadrocopter meeting that will take place on Aug. 21. in Bremen.