the electronics boards strapped to the outside of the model, maybe only
protected by heatshrink, or similar.
When you use high precision measurements for GPS, IMU and air pressure, I
think you will suffer very badly from temperature and temp gradient
effects on those boards.
We got caught with this in evaluating a GPS board. We put the bare
board on a bench out in the open, and logged the position and velocity.
Both drifted badly, about 20 times worse than the published data, and
lead us to a long argument with the manufacturer until we ( somewhat by
accident ) shielded the board from air drifts. The drift dropped
immediately to an acceptable level. Yes I know GPS is all 'digital',
but in fact there is a very critical component, the TXCO oscillator,
which must remain exquisitely stable for the system to work, and temp
drifts over a few seconds were badly upsetting it.
Precision analog components like gyros, accelerometers and pressure
sensors will also suffer from these effects. Think about what happens
as you fly a model through air currents, thermals, etc, all at different
temperatures.
It would not surprise me if some of the bad GPS and IMU data I see
reported are due to the same problems, especially on those bare boards.
My recommendation would be to put all boards in an aluminum box ( even
foil would help ), and then put that in an insulating container or foam
wrap. This would cut down the rate of temperature change, and probably more
important, the temperature gradient, across those sensitive components.
You need to be a member of diydrones to add comments!
Replies
My stuff is exposed right now, but I also am just doing initial testing.
For the final unit I have a nice thick plastic enclosure lined up with EMI shielding paint. Gyros and Accelerometers are usually temperature compensated and the way the DCM drift-correction algorithms are setup that kind of offset is generally slowly corrected for.
Most people's "alpha build .01" is unshielded out in the open, but I don't think a lot of people post photos after that point.
As Ken mentioned, the external shrink-wrapped component is the ESC, as well as systems using the XY and Z sensors, which must mount externally.
On this site you will see people flying through inclement weather, sometimes at amazing speed ranges, who do not seem to suffer from your perceived equipt vulnerabilities.
Again, most of the problem reports you mentioned can be traced to bad soldering or assembly errors.
I am sure we can assume that was the case with your project, but thanks for the suggestions anyway.
the electronics boards strapped to the outside of the model, maybe only
protected by heatshrink, or similar."
Many models? Really? I doubt that. Aside from Marcy, can you provide links to these GPSes and IMUs in heat shrink (or not) on the outside of the airframe?
If one is using the DIYdrones recommended platform, the autopilot electronics are inside the foam cockpit, the servos are exposed. The thermopiles, if used, need to be exterior to function. ESC's, often but depending on loading, need airflow for cooling so some people stick them outside. They are often wrapped in heat shrink. Are these what you are referring to?
I think if you read carefully, the majority of people having GPS and IMU issues haven't yet gotten off the assembly bench.