Meshtastic ABM Rugged RAK 4631/19007

ABM: Absolute Bare Minimum node. 

A compact Meshtastic node based on the RAK 4631 and the venerable Parametric Rugged Box by Whity. 

This enclosure is designed to support a wide variety of Meshtastic features and be compact enough to secure to the back side of any cheap “Security Camera” solar panel. Designed to leverage the solar panel's built in mounting hardware this node can hide almost anywhere. 

This is designed to be as bare bones as it can get and include more advanced features if you wish. 

It has been tested in the extreme wetness of the temperate rainforest of Vancouver Island, Canada and has held up to the elements while maintaining a dry interior for the electronics. Humidity has not exceeded 25% over 4 rainy west coast winter months. This is still an experimental design so use at your own risk. 

1 year update: This design is tested and proven. It has been out in the elements of a temperate rainforest for over a year and while the humidity has steadily gone up I have opened it several times and not replaced the desiccant at all. I am confident this is the most waterproof 3D printed Meshtastic enclosure available.

The 1 year of data speaks for itself. You can see where I opened the enclosure for maintenance by observing the humidity jumps. Its still well within the safe range at 70% humidity after 1 year. 

Bare bones this is a basic Meshtastic project. 

Including all the extras is an advanced Meshtastic project and you will have to do your own research into how to use these components if you are not familiar with them. It is very much worth it to include all the bells and whistles. 

Do not attempt this project if you are not comfortable with soldering, measuring voltages, circuit analysis, and other basic electronics skills. 

Recommended battery is a single 21700 cell but an 18650 will fit just fine as well. You can also use a single LiPo 3000mAh pouch cell and forgo the advanced components and the battery carrier. Secure the pouch cell with double sided tape. 

Bare Minimum Parts Required:

1. RAK Wisblock 4631

2. Solar Panel

3. Battery

4. Battery Holder

5. SMA to IPEX Antenna connector

6. RAK battery and Solar panel connectors 

7. 6x 35mm M3 Stainless Bolts. Do not use the black ones they will rust. 

8. RTV Black Gasket Maker

9. Desiccant Packets

10. Various Metric screws and bolts. M3 bolts, M2.3, M2.6 wood screws.

11. 90 degree bending sleeve dipole antenna for your region's frequency. Make sure its properly tuned. 

Optional Addons:

1. Voltaic Enclosures PCM module (Highly recommended unless you live somewhere very sunny)

2. SD05CRMA solar battery charge controller

3. RAK 1901 Temperature/Humidity Sensor (Highly recommended for every installation)

4. RAK 12002 Real Time Clock Module (Recommended for very remote installations)

5. Airtag for tracking if stolen

6. JST-PH connectors male and female. CHECK YOUR POLARITY BEFORE CONNECTING. 

7. JST XH 4 pin connector, Crimping Tool and Terminals. Or use DuPont if you hate yourself. Dupont will have trouble fitting due to connector size. Or just solder directly. 

Printing Tips:

1. Print the box halves and latches out of PETG or ASA. I used PETG for superior layer adhesion and painted for UV Protection.

2. To ensure water tight printing set your extrusion multiplier to 1.10 and set your top/bottom/wall settings to print the box nearly solid. This will ensure good overlap of the extrusions and lead to a water tight box.

3. If you do not follow these instructions it will leak. 100% guaranteed. 

4. Print the node and battery carrier units out of whatever. I just used PLA. 

Assembly Tips: 

This is all from memory so there will be some figuring it out as you go. This is for the full monty. Just ignore the parts about the parts you choose not to use. 

1. Print all the parts required. If you are not using the PCM Module, INA219, or SD05CRMA you can forgo the battery carrier unit and just tape/glue your battery and holder to the inside of the lid. You may be able to squeeze in 2x18650 this way. 

2. Using RTV Gasket Maker with the included nozzle and toothpicks jam as much RTV into the gasket groove on the box as possible. You do not want any voids in there. Level it with a putty knife. DO NOT CLOSE THE TWO HALVES TOGETHER

3. Leave the RTV to cure for 24 hours. 

4. Assemble the box as per the Rugged Box instructions

5. Either solder your battery holder to the SD05CRMA charger and then solder the BAT connector for the Voltaic PCM to the battery holder or make yourself a pigtail with 1 end soldered to the charge controller, 1 end soldered to the battery holder,  and 1 end with JST-PH Female connector with the correct polarity for the Voltaic Enclosures PCM. Leave slack on the positive wire if you are using the INA219. 

6. The key here is that the charge controller, PCM module, and battery are all wired in parallel. This way the charge controller will charge the battery no matter what and the PCM will cut off power to the node if the voltage is too low. 

7. Slide the SD05CRMA into the little slot shaped like it on the battery carrier.

8. Use M3 bolts to screw the Voltaic Enclosures PCM to the battery carrier. 

9. Solder the JST-XH and screw terminals onto your INA219 unit. Or just solder the wires right on, whatever works for you. 

10. Use M2.6 self tapping screws to secure the INA219 to its location on the battery carrier

11. Glue or tape or screw your battery holder to the battery carrier

12. If using the INA219 snip the positive wire to the battery, strip back 1/8" of insulation and tin the tips of the wires. Install them in the VIN+ and VIN- terminals of the INA219. VIN- goes to the battery.

13. Solder your JST-XH connector on to the RAK's I2C, VCC and GND Pins. 

14. Cut your wire for the INA219 to RAK I2C cable, crimp and insert. You want to keep this short but have enough room to open the box. 

15. Install any extra Wisblock Daughter Boards you wish. I highly recommend at least the RAK 1901 temp/humidity sensor to monitor for leaks. This is a 3D printed box after all and it may not be perfectly sealed.

16. Use the RAK provided mounting screws to screw the RAK board to the RAK Carrier. 

17. Use a ¼" drill bit to round out the hole for the SMA connector. Its designed to print too small and requires drilling out to make it round and give a good seal. 

18. Before going any further fully assemble your carriers outside of the box. Make sure everything works properly. Test it for a day or two if needed. Once it goes in it can't all come out easily. Especially the battery carrier.  

19. Insert the RAK carrier with the RAK on it into the bottom of the box. The carrier should fit nice and snug and not need any fasteners. However holes for M3 fasteners have been included if you need them. 

20. Slather the base of your SMA connector with RTV. This is needed to seal it. Push it though the SMA hole and use a 5/16" deep socket to screw on the nut and washers. Make sure you seat the SMA base correctly in the printed hexagonal socket. The RTV should ooze out nicely and give you a good seal. Clean up any excess RTV.

21. Insert the battery carrier. into the lid. Screws optional. 

22. Cut the USB connector off of your solar panel. Make sure to leave lots of slack. 

23. Measure your cable thickness and use an appropriate size drill bit to enlarge the cable hole in the lid as needed. Do not drill it out too much. You want a very snug fit for water tightness. 

24. Insert your solar panel cable into the hole. Solder on your RAK solar panel connector if going right to the RAK or solder to the SD05CRMA  charging board. 

25. Slather tons of RTV around the solar cable where it enters the box. Pull it into the box a little more to pull some RTV into the hole for extra sealing. Clean up any excess. 

26. Connect your antenna to the SMA connector, connect your RAK Bluetooth antenna to the RAK and use its adhesive backing to secure it to the inside of the case. 

27. You should have everything fully assembled in the box. Close it up and check for fitment issues. if there are any defects or voids in your gasket around the box edges fix them with more RTV and let it cure. 

28. Use double sided gorilla tape (highly recommended), JB Weld, whatever to affix the box to the back of the solar panel. Pay attention to which way the box opens to avoid interference issues. Switch which side your latches attach to if needed. 

29. Before you close it up make sure to put in as many desiccant bags as you can. Fill that sucker up. Carefully microwave the desiccant bags for short 45 second bursts to super dry them. Be careful you can light them on fire or melt them in the microwave. Paper bags are recommended, not plastic. 

30. I put an airtag in mine to track if it gets stolen. Totally optional. 

31. Put it outside and leak test the hell out of it. I mean spray it with a hose, leave it in the rain for a month, whatever. You want to make sure the printed box is doing its job at being waterproof.  

32. Paint it for UV protection. I was putting this one in a tree so I used camouflage paint. Beautitone Camo Coat is a good brand and transparent to radio waves. 

33. Now that you've validated it won't leak in the rain go forth and screw it to a tree, fence post, whatever. Make sure you have permission if not installing on your own property. 

34. After mounting the panel mount base orient the panel for maximum solar exposure under your worst case conditions. EG: Winter. If you live somewhere that's cloudy all winter, aim the panel more at the sky than the direction of the winter sun. This will get you more indirect light off the clouds. If you live somewhere with short but clear winter days orient the panel so it is perpendicular to the sun at mid day on the winter solstice. Use the INA219 output metrics to figure out the best orientation for your panel in your average conditions. Don't orient it for optimal angle to the sun if you live somewhere its cloudy all the time. Orient it in the direction you get the most current under your worst conditions. This can be counter intuitive but the INA219 will help you figure it out. 

35. Once you figure out the panel orientation orient your antenna so it is straight up and down. Use some self amalgamating tape to secure it so it does not rotate horizontal in the wind. 

36. Congrats, you're basically done with this very long tutorial. 

Happy Meshing!