Quick recommendation for embedded system - Page 1
Forum section: electronics / general

author: calexanian
author_rank: Super Contributor
timestamp: February 14, 2018, 05:07:07 pm
content: Need a quick recommendation for an embedded computerThe application is an in field industrial/agricultural environment. so wide temp range durable things that will be available or easy to replace with then modern bits many years from now.Currently working with Raspberry pi compute 3, but worried about future availability of the form factor and looking at alternatives. Very minimal memory requirements. Stripped down linux and a web app with local UI and I/O. Considering just jumping up to a micro ATX board, lots of cost and overhead, but molecularity for future iterations. Could just go to whatever the next RbPi for beagle bone, etc, but every 18 month or so would have to make a minor re design, or pray they don't change that much. Also would need to re test and re qualify for any funky I/O ness on those boards with every new version. Looking at possibly just using the sbc as a brain then everything real world sending out to a pic for all peripheral handeling, accept display so only data is sent back to the sbc side stepping any GPIO possible fussyness.Thoughts?

author: Ampera
author_rank: Super Contributor
timestamp: February 14, 2018, 06:54:16 pm
content: I'm gonna make one suggestion. USB.USB is a standard introduced in the mid-late 1990's, and is incredibly ubiquitous to this day. If you can, in any way, get something to function over USB, even if it's just using an RS-232 serial emulator, which are also incredibly ubiquitous (Heck, even RS-232 might not be a bad idea) use it.There exist few computers on the market without USB support, and I imagine it's going to be around long enough to make future replacements of any peripherals or main systems a lot easier.As for the basis of what machine to use, use x86. It's been around in the IBM PC compatible basis since 1981, and will NEVER be hard to come by until decades after it's death. If you are looking for a robust route to go, with ease of finding replacement parts in the future, x86, and USB. Those two will not die for a long time.

author: VK3DRB
author_rank: Super Contributor
timestamp: February 16, 2018, 02:04:50 pm
content: You want something robust? Forget the Raspberry Pi. It lacks input protection and is subject to ESD damage amongst other issues. In short, it is designed for the hobby market at a hobbyist price; not for robust industrial applications like agriculture.I would suggest an industrial SBC (Single Board Computer). There are many available from numerous vendors that have term product roadmaps. For example, you can buy the same boards 10 years after their first release. For low cost and excellent support, consider VIA Technologies micro ATX. I have used them in an industrial design. You can run QNX, Linux, or if your really have to the crappy Windows. SBCs are generally of a robust hardware design. Not great performers compared to fast PCs for gamers, but very robust, small and functional.If the product you are designing is high volume, consider the OMAP TI like the AM3352 Sitara processors running Linux (Beaglebone), and embed it on your own PCBA.

author: calexanian
author_rank: Super Contributor
timestamp: February 17, 2018, 06:46:07 pm
content: I had looked at the VIA boards. They do not offer the temp range we require. It would have been an ideal solution. Industrial temp range pc motherboards are too expensive for this application. Looked at the Sitara processors but we don’t want to design our own board for them. Unless we had a ready toDrop in layout we could never design one in house to meet EMC testing. We have no experience in things that zippy. I suppose we could farm it out, but we are small and do not have the resources of a large company.

author: VK3DRB
author_rank: Super Contributor
timestamp: February 18, 2018, 10:07:27 am
content: Have you considered temperature mitigation for a VIA (or any other) motherboard? Most VIA boards come with fans. I don't know what your environment will be (very hot, very cold or very dirty). You could use Peltier devices to cool or heat the enclosure. They are easy to use, but generally draw quite a bit of current and you might need to heatsink them, and at least have a simple current switching control mechanism. In my previous job, I used Peltier devices to very accurately control the temperature in SHG lasers; to maintain a temperature typically within 0.1 deg C. Worked a treat, and very reliable. Peltiers work well too in high IP rated enclosures; ie: water and dust ingress protection, where you don't want to use a fan with a filter to the outside world.

author: nali
author_rank: Frequent Contributor
timestamp: February 18, 2018, 10:18:18 am
content: What budget? Generally speaking at one end of the spectrum you get the cheapie RPi etc, the other is the fixed BoM guaranteed lifespan product - for which you pay $$$You could consider a system-on-module approach; you can then design the host board with whatever IO etc you need. If a module is EOL'd or modified the worst you would have to do is respin the board.

author: Halcyon
author_rank: Unknown
timestamp: February 19, 2018, 05:32:31 am
content: Quote from: TwoOfFive on February 14, 2018, 06:54:16 pmI agree in a sense however I'd be very careful about relying on USB for I/O in industrial applications. I've worked on vehicle-mounted computers which used all kinds of peripherals and USB was a pain in the ass at times, mainly due to the physical connection itself. It's not designed for use in applications where there is constant movement, vibration, knocks/bumps etc... We found that a lot of the connectors wiggled their way loose or just didn't make proper contact 100% of the time (for example, driving over speed humps).You can getindustrial USB connectorswhich feature proper seals and locking mechanisms, if you are going to use USB, I'd be going with something like that.

author: calexanian
author_rank: Super Contributor
timestamp: February 19, 2018, 06:29:35 am
content: Normal USB connections are out of the question. This is an agricultural application in direct sunlight in an IP 67 enclosure. I have found it to be nearly the worst possible environment for electronics. Corrosive chemicals in the way of fertilizers and chlorine are used, along with caustics as well. solar loading in excess of 70 degrees occur in summer months. The most damaging element though is human. Somebody simply forgetting to shut the door for months on end is the most common failure mode. Would you set your PC in a dirty field and expect it to last long? If they just keep the darn thing closed and reasonably clean there is no reason they cannot get 20 years out of our current products. I have seen them come in as soon as a few months with the solder mask peeling off and green copper oxide all over because they left the box open and the pesticide, or organic fertilizer truck came by and sprayed the pcb.

author: nctnico
author_rank: Super Contributor
timestamp: February 19, 2018, 11:52:23 pm
content: Quote from: nali on February 18, 2018, 10:18:18 amSystem on module could be a reasonable approach if the volume is small (say 100 to 200 units). Otherwise going full custom is cheaper in the long run. Developing the software will be a big task anyway because even though system on modules comes with a board support package this often isn't production grade software.