Hi, I am designing an automated control of an observatory dome and I need a component to show observing door heading. I bought an electronic gyro + accelerometer, but had an epiphany that it was not what I needed. A magnetometer is more suited to my system, maybe a combination of all is the best, dont really know how to utilize them all though.
Now, I have searched and there seems to be several ones to choose from, so I ask the forum for tips on which one to buy. I need it to have little periodical error (maybe the accelerometer will help with that), and have an accuracy of 1 degree at least.
HMC6352, HMC 5883L, LSM303, MPU-9250 are some of the options, but I am happy to get other recommendations, of any price class too!
Many thanks in advance
Regards, Runar from Norway
Assuming that the observatory is actually stationary, I would guess an encoder makes more sense than a compass - or some servo perhaps fed with the same azimuth data as the telescope.
The arduino is going to comunicate with a computer that recieves a new coordinate from a telescope mount, programmed with ASCOM standard.
A target is chosen on the telescope or a computer program like skymap, and the AZ position is sent to the arduino master unit, which receives an actual heading of the opening from a slave unit via bluetooth. The slave unit is going to be used for remote control of the opening anyways, so I thought this would be the easier, and more reliable implementation if done right.
Observatory is stationary yes, but the system I am installing is an expansion of the manual electrical control already installed.
RunarSJ:
Observatory is stationary yes, but the system I am installing is an expansion of the manual electrical control already installed.
Then you are screwed if you want minimum deviation. ALL electrical current produces a magnetic field around the conductors and will affect your compass.
Paul
I know this, been fed this information with a silver spoon for over 8 years now. It's a matter of how strong the currents are, the compass is not close to the biggest component in the system. I just want tips on which compass I should use.
i've had nice experiences with MPU9250, low deviation and almost no drift... but i can't know if it is the best solution for your application
Do you have any measure on drift? Would it drift considerably after, say an hour?
The latest crop of magnetometers have very similar characteristics. If properly calibrated in their final environment, you can expect at best about +/- 1 degree accuracy, used as a compass.
The main issues with stability will be variations in temperature (a surprisingly large effect) and of course, in the surrounding magnetic field.
A comprehensive overview on the best currently available calibration methods can be found at Tutorial: How to calibrate a compass (and accelerometer) with Arduino | Underwater Arduino Data Loggers.