Hello fellow genmon enthusiasts!
I had noted a few other "this is my implementation/execution" type issue posts here so I thought it might help someone to see how I did it. Plus it's fun to brag. 馃檪
First off, many, many thanks to JGY for his incredible accomplishment, and for the super support he brings to the community, which is clearly evident when perusing the issues section of this project.
I would have jumped on this bandwagon two years ago when it all started, but I only just became aware of the project, quite by accident, on my Google news feed just a few weeks ago.
It seemed clear that this was a project perfect for the Pi Zero platform. I would have gone full hardwire PoE but there is zero room left in the wire conduits to my generator, a 2011 vintage Generac 17KW unit running on propane. Needing WiFi, I quickly found that Pi Zero W's were currently unobtanium. Even Zero 2 W's were hard to find, but I did get one for the standard price of $15. And I was happy to see that the Nexus provides 5V, so no worries about fussing with power supplies. All things considered, this is actually a simpler and much less expensive approach than pulling another cable from my switch and integrating a PoE hat.
I wanted the smallest footprint easily possible. By easy that meant minimal mechanical fabrication and obtainable from Amazon (Prime, free shipping, free returns if I hated it, all that sort of thing). I found this very nice, highly rated RS232-TTL level translator board which would easily nest within the outline of the Pi Zero: https://www.amazon.com/dp/B07BJJ3TZR
Using that board I could probably have fit the darn thing in a large pill bottle. I seriously considered just putting the two boards back to back and dunking it in Plasti Dip. But ultimately I decided I wanted something a bit more repairable, just in case. I found this very small, IP68 rated, junction box on Amazon that seemed perfect: https://www.amazon.com/dp/B07TFSLLBY Having built many systems in my career that meet MIL-STD-810, the nice gasketing and molded in cable glands were a big draw. It was plastic, so no worries about the on-board WiFi antenna on the Zero. No shielding was a slight worry, but it did not turn out to be a problem. The extra cable gland would be perfect to captivate an external WiFi antenna if required. As already noted it was not necessary. My nearest WAP is quite near, and signal levels are right around -60dBm in both directions per the Pi and the WAP. The extra gland was sealed up by the simple expedient of putting a large brass bolt into it and tightening the gland down.
Of course I also used the cable assembly recommended on the genmon wiki, as it was cheaper and easier to get it from Amazon than ordering the parts from Digikey or Mouser: https://www.amazon.com/dp/B000M802RG Their shipping always kills you, and adding pigtails of the right wire gauge was not any harder than crimpling contacts, if somewhat less elegant. I did think about getting some jacketed cable that would work better with the cable gland, but sometimes perfection is the enemy of good enough.
I had originally thought I would attach the level translator board back to back with the Pi using some high-bond, double-sided tape, then screw down the Pi into the case. But that would disturb the watertight integrity of the case, and it turned out that the two boards fit perfectly onto the case lid. By using two layers of tape, the boards stand proud of the lip on the lid thereby providing easy access, without any further disassembly, to the SD card and other ports should future maintenance be necessary.
If the boards look a little weird, that's because they are mostly covered in a urethane conformal coating: https://www.amazon.com/gp/product/B008OA7AWE This will protect the covered areas from any condensing humidity, and there will be plenty of that in an outdoor application like this. IP68 does not mean hermetically sealed. I did not add a drain (weep) hole to the box, and we'll see how that goes. The level translator board is slathered front and back, as is the back of the Pi, but it's not possible to do that on the front of the Pi without damaging the connectors and ports.. The front of the Pi is carefully coated to avoid those areas. Urethane doesn't look as pretty as acrylic conformal coat, and doesn't flow out as well, but it's easier to apply with no masking or back-potting of connectors. I did mask the WiFi antenna footprint with a bit of Kapton tape, just in case I want to add that in the future, but so far it appears unnecessary.
Waxing a bit more poetic about conformal coating, I've had two throttle stepper motor failures in this generator. Both times it was corrosion of the poorly made, completely uncoated, solder joints on the junction PCB inside the stepper motor. When the spare failed I cracked them both open, found the problem, re-soldered both, and urethane coated the boards. I haven't had a lick of trouble since then.
Installation isn't fancy. I plugged it in and rested the box on an existing wire harness. This seems more than secure enough. Simple, and out of the weather. The little junction box is very light, and by doing it this way it avoids any vibration the box would be subject to if it were rigidly mounted to the generator structure. Again, my nearest WAP is only about 20 feet away and signal strength has not been a problem. EMI has also not proven to be a problem, perhaps because of the very short cable length. However, the Pi certainly is as snug as a bug, showing a CPU temperature rise of approx. 50掳F degrees above ambient on a cloudy day (e.g. running 90 on a 40 deg. day). It will be interesting to see how that pans out on a 95掳F summer day with the generator running. Some cooling modifications may prove necessary. 馃敟**If anyone has any tips/hints on how to maybe slow the processor down in order to lower its temperature they would be most welcome.**馃敟
Total expenditure was only $39: $15 for the Pi, $8 for the level translator, $7 for the cable assembly, and $9 for the junction box. Got to love free Amazon shipping! Everything else I already had: wire, tie wraps, shrink tubing, solder, flux, coating, etc.
I'll wrap this up with a schematic. I was quite fussy about paying attention to serial signal paths. I never trust "TXD" and "RXD" labels.
Cheers and Happy New Year to all!
Hello fellow genmon enthusiasts!
I had noted a few other "this is my implementation/execution" type issue posts here so I thought it might help someone to see how I did it. Plus it's fun to brag. 馃檪
First off, many, many thanks to JGY for his incredible accomplishment, and for the super support he brings to the community, which is clearly evident when perusing the issues section of this project.
I would have jumped on this bandwagon two years ago when it all started, but I only just became aware of the project, quite by accident, on my Google news feed just a few weeks ago.
It seemed clear that this was a project perfect for the Pi Zero platform. I would have gone full hardwire PoE but there is zero room left in the wire conduits to my generator, a 2011 vintage Generac 17KW unit running on propane. Needing WiFi, I quickly found that Pi Zero W's were currently unobtanium. Even Zero 2 W's were hard to find, but I did get one for the standard price of $15. And I was happy to see that the Nexus provides 5V, so no worries about fussing with power supplies. All things considered, this is actually a simpler and much less expensive approach than pulling another cable from my switch and integrating a PoE hat.
I wanted the smallest footprint easily possible. By easy that meant minimal mechanical fabrication and obtainable from Amazon (Prime, free shipping, free returns if I hated it, all that sort of thing). I found this very nice, highly rated RS232-TTL level translator board which would easily nest within the outline of the Pi Zero: https://www.amazon.com/dp/B07BJJ3TZR
Using that board I could probably have fit the darn thing in a large pill bottle. I seriously considered just putting the two boards back to back and dunking it in Plasti Dip. But ultimately I decided I wanted something a bit more repairable, just in case. I found this very small, IP68 rated, junction box on Amazon that seemed perfect: https://www.amazon.com/dp/B07TFSLLBY Having built many systems in my career that meet MIL-STD-810, the nice gasketing and molded in cable glands were a big draw. It was plastic, so no worries about the on-board WiFi antenna on the Zero. No shielding was a slight worry, but it did not turn out to be a problem. The extra cable gland would be perfect to captivate an external WiFi antenna if required. As already noted it was not necessary. My nearest WAP is quite near, and signal levels are right around -60dBm in both directions per the Pi and the WAP. The extra gland was sealed up by the simple expedient of putting a large brass bolt into it and tightening the gland down.
Of course I also used the cable assembly recommended on the genmon wiki, as it was cheaper and easier to get it from Amazon than ordering the parts from Digikey or Mouser: https://www.amazon.com/dp/B000M802RG Their shipping always kills you, and adding pigtails of the right wire gauge was not any harder than crimpling contacts, if somewhat less elegant. I did think about getting some jacketed cable that would work better with the cable gland, but sometimes perfection is the enemy of good enough.
I had originally thought I would attach the level translator board back to back with the Pi using some high-bond, double-sided tape, then screw down the Pi into the case. But that would disturb the watertight integrity of the case, and it turned out that the two boards fit perfectly onto the case lid. By using two layers of tape, the boards stand proud of the lip on the lid thereby providing easy access, without any further disassembly, to the SD card and other ports should future maintenance be necessary.
If the boards look a little weird, that's because they are mostly covered in a urethane conformal coating: https://www.amazon.com/gp/product/B008OA7AWE This will protect the covered areas from any condensing humidity, and there will be plenty of that in an outdoor application like this. IP68 does not mean hermetically sealed. I did not add a drain (weep) hole to the box, and we'll see how that goes. The level translator board is slathered front and back, as is the back of the Pi, but it's not possible to do that on the front of the Pi without damaging the connectors and ports.. The front of the Pi is carefully coated to avoid those areas. Urethane doesn't look as pretty as acrylic conformal coat, and doesn't flow out as well, but it's easier to apply with no masking or back-potting of connectors. I did mask the WiFi antenna footprint with a bit of Kapton tape, just in case I want to add that in the future, but so far it appears unnecessary.
Waxing a bit more poetic about conformal coating, I've had two throttle stepper motor failures in this generator. Both times it was corrosion of the poorly made, completely uncoated, solder joints on the junction PCB inside the stepper motor. When the spare failed I cracked them both open, found the problem, re-soldered both, and urethane coated the boards. I haven't had a lick of trouble since then.
Installation isn't fancy. I plugged it in and rested the box on an existing wire harness. This seems more than secure enough. Simple, and out of the weather. The little junction box is very light, and by doing it this way it avoids any vibration the box would be subject to if it were rigidly mounted to the generator structure. Again, my nearest WAP is only about 20 feet away and signal strength has not been a problem. EMI has also not proven to be a problem, perhaps because of the very short cable length. However, the Pi certainly is as snug as a bug, showing a CPU temperature rise of approx. 50掳F degrees above ambient on a cloudy day (e.g. running 90 on a 40 deg. day). It will be interesting to see how that pans out on a 95掳F summer day with the generator running. Some cooling modifications may prove necessary. 馃敟**If anyone has any tips/hints on how to maybe slow the processor down in order to lower its temperature they would be most welcome.**馃敟
Total expenditure was only $39: $15 for the Pi, $8 for the level translator, $7 for the cable assembly, and $9 for the junction box. Got to love free Amazon shipping! Everything else I already had: wire, tie wraps, shrink tubing, solder, flux, coating, etc.
I'll wrap this up with a schematic. I was quite fussy about paying attention to serial signal paths. I never trust "TXD" and "RXD" labels.
Cheers and Happy New Year to all!