Meshtastic Absolute Bare Minimum Node Smoker's Section

The evolution of the ABM -- Absolute Bare Minimum Node. 

This node uses a waterproof cigarette case/lighter as its enclosure with printed node sled and case holster. Glue the completed unit on the back of any "security camera" solar panel and get a super reliable and stealthy node that can go almost anywhere. 

BOM: 

1. Waterproof Cigarette Case: https://www.aliexpress.com/item/1005006005718935.html

2. CDSNET Blade style antenna. Beware of similar looking antenas. This brand usually comes well tuned: https://www.aliexpress.com/item/1005003292986302.html

3. RAK 19007/19003 with 4631 board. I think it will fit a RAK 3400 1 watt but you will need a longer SMA pigtail

4. 10cm SMA pigtail, with the skinny cable

5. Power wires for the RAK battery and solar. CHECK YOUR POLARITY BEFORE APPLYING POWER. 

6. Cheap battery PCM module as insurance(for unprotected cells) https://www.aliexpress.com/item/32674039738.html

7. 21700 5Ah battery

8. 8mm nickel battery welding strip

9. Security Camera 5 volt solar panel. Check you panel open circuit voltage in full sun. The RAK can only take up to 6.5 volts safely. Instructions included for if you get a 7.5 volt panel. 

Optional Components:

1. Adjustable Buck Converter (If you happen to have a panel over 6.5 volts open circuit) Any cheap buck converter will do but an adjustable one lets you get the most current by setting it to 6.5 volts: https://www.aliexpress.com/item/1005006351165221.html

2. INA219 Voltage/Current Sensor. Monitor your power in/out: https://www.aliexpress.com/item/1005007533576335.html

3. RAK 1903 Temperature/Humidity Monitor or BME680 sensor to monitor for moisture. A must if you live in a moist area. 

4. SD05CRMA MPPT solar charge controller. Increase your charging efficiency: https://www.aliexpress.com/item/1005007549860340.html 

5. Voltaic Enclosures PCM board. Not strictly needed any more but nice insurance in cloudy locations: Li-ion Battery Protection Modules (PCM) and Cables - 2.9v (3v) Over Discharge Cutoff - for Lithium Ion Cell - Etsy Canada

6. GORE knock off vent. M5x0.8-7: https://www.aliexpress.com/item/1005006370919409.html

Instructions

Instructions are for the bare bones setup. There are sleds included for protected 20750 battery and the "full meal deal" with mounting locations for all the optional components. 

Node Carrier Sled

1. Print the Panel Back Case. No supports needed standard 0.4mm nozzle 0.2mm layer height. Slow the print down to avoid VFAs if you care. 

2. Print the Node Carrier sled of your choice

3. Assemble and test your RAK board and sensors

4. snip off the protruding legs of the battery and solar connectors on the underside of the board.

5. Using a hobby knife clean up the 2 slits at either end of the battery holder portion. They may print cleanly but even on a Bambu P1S I needed to clean them out a little to get the nickel strips through

6. Cut 2 sections of nickel strip, about 1 inch long. You will trim these to fit later.

7. Using a thin screw driver as a jig bend the nickel strips into a u shape

8. Carefully push the nickel U strips from the inside through the slits on either end of the battery carrier. 

9. Fold the ends over and trim to leave enough room for soldering

10. Solder short wires on to to the B+ and B- pads on your PCM board so that it can sit on the side of the battery holder. Pay attention to the polarity. The inside of the battery case has + and - printed in it. + is at the bottom of the sled; opposite the RAK USB Port.

11. Screw your RAK down using the provided RAK screws or better yet some M2.6 6mm wood screws. 

12. Measure and trim your RAK battery cable so that it can exit one end of the PCM board. Solder the B- wire to the - side nickel strip. Leave the positive wire unsoldered

13. Slip some heat shrink over the PCM board and shrink it down. 

14. Solder the B+ wire of the PCM to the + nickel strip

15. Check the polarity with your multimeter! Double check the wires are in the right side of the PH 2.0 connector. Swap the wires if needed. 

16. Insert your solar charging cable into the solar port. CHECK THE POLARITY. 

17. Insert the battery making sure the polarity is correct. Battery + opposite the USB port. Its a tight fit and you need to place the battery flat on a table and gently push the carrier straight down on to it. 

18. Connect your solar port wires to an appropriate power supply and check it is charging the battery. 

Supplemental on Panels

If you find you get a panel that provides more than 6.5 volts across the bare wires in full sun you need to step the voltage down for the RAK or use a SD05CRMA charger board. For a buck converter solder the solar port wires to the appropriate terminals and use double sided gorilla tape to tape the buck converter board to the sled below the RAK. 

Final Assembly

1. Take your cigarette case and remove the lighter part in the lid. 

2. Carefully make a mark on the lid, opposite side of the latch. 5mm exactly from the ridge. 

3. Use a 1/16" drill bit to make your pilot hole for the SMA connector here. 

4. Keep drilling the hole slowly with increasing size drill bits until you are at a 1/4" hole. Go slow this is soft plastic. 

5. If using a vent drill a hole in the front  of the lid, about 15mm from the top. Same deal as before, start with 1/16" drill bit and work your way to 7/32". If you have a M5x1 tap you can use it to tap thread holes for the vent but this is only for the extremely pedantic mesher. 

6. Insert your SMA pigtail most of the way into the 1/4" hole. Stop. 

7. You need to make sure the cable wont be stressed when the node is installed. Slide your node carrier in to the case with the battery side opposite the hinge. 

8. Figure out the best rotation of the SMA connector to have the least stress on the IPEX connector. You want the IPEX connector and cable to make a nice U shape towards the bottom of the case when you close the lid.

9. Slather glue or epoxy around the base of the SMA connector on the inside. I like clear Gorilla Glue for this as it is somewhat flexible.

10. Push the SMA connector all the way through. Put some more glue/epoxy around the base of the connector on the outside. Be careful to not get any on the top of the connector. 

11. Grip the inside hex nut with needle nose pliars and install the locking nut hardware on the outside of the SMA connector. Use a 5/8 deep socket on a screw driver to screw down the not while using the needle nose pliers to make sure you keep the right rotation of the SMA connector. This is crucial to getting good results. 

12. Install your vent with the same glue/epoxy you used for the SMA connector. 

13. Set the case aside to dry/cure.

14. When the SMA and Vent glue/epoxy are good and cured proceed

15. Take the Panel Back Case and epoxy it to the back of your solar panel. Use epoxy not glue for this. I like clear JB Weld.

16. Be sure to leave enough spacing your antenna will clear the side. Don't worry if your panel back is curved, the epoxy will take care of everything if you use enough of it.

17. Lightly clamp the panel and Back Case together. If you don't the case will move and go off kilter. 

18.  Leave it all to cure. 

19. Once cured you can insert your cigarette case node into the Panel Back Case. 

20. Now is when you have to trim and install your power wire from the panel. 

21. Snip off that USB-C connector. You wont need it any more. 

22. You want to leave a lot of slack on the wire so you can open the case still.

23. Above the latch side of the case drill a 1/16" pilot hole. 

24. Keep drilling with increasing size and frequently test fit your wire in the hole. You want a hole that is the tightest fit for the wire possible. Wire size varies across panels so check frequently. 

25. Once you have an appropriate size hole force your solar panel wire through

26. Figure out how much slack you need on the wire so you can easily open the lid without stressing the point the wire enters the case lid. 

27. Trim the wire inside the lid leaving enough slack for you to strip back the outer insulation and strip enough off the + and - wire to solder your solar port connector to or solder to the buck converter. 

28. STOP

29. Using your multimeter double check the solar panel polarity. Don't assume Red means +. Some of these cheap panels are wired backwards. 

30. Once you confirm polarity out of the solar panel solder the wires to the solar charger connector or buck converter. 

31. Congrats, you are done. Screw in the panel mount the panel came with and mount your node.  

Or you can paint it camo like I did for the ultimate stealth tree node. 

Make sure to microwave some desiccant packs and stick them inside to keep it dry. And use printer grease around the lid/seal to give some extra waterproofing. 

Happy Meshing!