Some forms of prototyping predominantly focus on proof of concept, after which the design undergoes refactoring for the production system.
Is this going to be such an approach, or is the focus going to be trying to select production system components the first go-around to the extent practicable?
If the latter, what environmental conditions should we be shooting for?
Min temperature is something not likely to play in significantly unless the robot will be left in field year round, but +65°C is a reasonable max component temperature target with an assumed +55°C ambient in field max. Near the solar panel, a +85°C rating can be warranted if parts are enclosed with little to no airflow between them and the panel.
Gusts up to 60mph are real (rare) in California, though up to 45mph is more common, typically once every 2 years. 20mph winds are common during spring and fall, with gusts of 35mph very common.
It is possible for rain to ingress in at 45° angles during a storm, but washdown rating should be planned for since a user will likely just spray clean the robot. This also provides submersion rating up to 3ft.
Yes we’ve had our fair share of wind in California and the prototype solar panel hold downs weren’t quite sufficient during some of the storms. (V2 has them very secure as we want to be able to transport them in a road trailer)
The next version of the system is designed for small volume production with an intent to survive outdoors in adverse conditions. We plan to sell V2 units as “functional prototypes” so they need to be able to survive without a bunch of maintenance. We will then iterate and replace parts in the design as we improve things.
As far as weather sealing we have a few subsystems that are of most concern:
I do not have specific parameters for min/max temperature etc. All our vehicles will just live outside in the rain, get washdown as needed, etc, and as we see failures we will improve things. I did work as a software engineer on a hardware reliability testing team at Google, so I’ve seen how a well funded team does reliability testing. As we grow beyond functional prototypes, we will want to start doing more intensive reliability tests. I have some basic test stands we’ve built here, but they need more work.
Operating temperatures are certainly a major consideration, though so are storage temperatures. These will likely be stored in unconditioned, uninsulated tool sheds or the like during non-working seasons. The temperatures seen by the Plains States all the way down to Texas recently should be an indication of what we should look for in min non-operating temperatures. Would the end product be targeted to Minnesota, Wisconsin, Michigan, Iowa, Montana, the Dakotas, and/or Nebraska?
The JetsonAGS Xavier has an operating temperature limit of 80C. I have not yet found a minimum temperature.
That’s a reasonable question, the minimum storage temperature. For most electronics it’s -35°C or lower. Epoxies used after board assembly may have higher minimums, and some electronics have -135°C or lower storage and operating. Generally the limit is based on the thermal expansion matching of the encapsulation material over the die and also the ability of the encapsulation material to survive.
From the Raspberry Pi FAQ:
“The Raspberry Pi is built from commercial chips which are qualified to different temperature ranges; the LAN9514 (LAN9512 on older models with 2 USB ports) is specified by the manufacturers as being qualified from 0°C to 70°C, while the SoC is qualified from -40°C to 85°C. You may well find that the board will work outside those temperatures, but we’re not qualifying the board itself to these extremes”
From the LAN9514 datasheet;