Harbor Breeze Solar T114 Meshtastic Node

While looking at designs for solar powered Meshtastic nodes, I came across a few builds using the Harbor Breeze 60LM Solar Flood Light. Since I didn’t need to keep the light, and wanted more flexible mounting options, I designed a replacement back cover, retaining the built in 18650 battery holder and power switch, adding mounting points for a Heltec Mesh Node T114, knock-outs for an SMT antenna, and holes for M6 heat-set inserts.

Parts/Bill of Materials

• Harbor Breeze 60LM Solar Flood Light (Item #2483282, Model #SL1832) - $10
• Heltec T114 (no screen) - $25-40 
• Antenna with SMA Pigtail) - $5-10
• Optional M6 (1/4-20) Heat-Set Insert(s)

Printing

While this model should normally be printed using PETG, I have used PLA with success for locations without constant sun exposure. When printing the back cover in PETG, supports should normally be used for the fluted sides and the screw holes. The 3MF file has individual components blocking the antenna holes, allowing you to remove one and print with a hole already in place. Otherwise remember to drill out the desired antenna hole before mounting components inside. In addition to the back cover, a weather-sealing plug for the USB-C port is also included, which should be printed using TPU.

Warnings

• Before disassembling your Harbor Breeze Flood Light, confirm it powers up (and the battery is good) by clicking the button on the rear of the case. You will need to do this at night or in a dark room, as any significant light on the panel will prevent the LED from turning on.
• Do not apply power to a T114 board before connecting the SMA pigtail and an antenna. Powering the board without an antenna attached could damage the LoRa radio.
• Do not finish assembly until you have loaded Meshtastic firmware onto the T114. The factory firmware normally requires use of the hardware buttons to upload firmware, but this will no longer be required once Meshtastic firmware has been loaded.

Assembly

1. Un-screw the lens cap from the Harbor Breeze light, remove LED/reflector, and clip the 2 wires attached.
2. Remove/save the 4 small screws holding the rear panel in place.
3. Remove the rear panel, clear glue/caulk around LED wires and pull them thru the hinge.
4. Remove the 18650 battery, and use pliers to remove the metal contacts from the battery holder
5. Unscrew the charger/button board, saving the screws and button/gasket.
6. Desolder the solar panel leads from the charger/button board.
7. Solder one of the JST 1.25 pigtails (included with the T114) to the wires from the solar panel. Following the symbols on the back of the panel, connect red to positive, black to negative. Use heat shrink tubing to insulate the connections.
8. Desolder the LED and battery wires from the charger/button board.
9. Solder the black battery contact wire to the black wire on the second JST 1.25 pigtail, using heat-shrink tubing to insulate.
10. Using pliers and a soldering icon, remove most if not all of the components from charger board, except for the button.
11. Using a multi-meter, find 2 contacts on the back of former charger/button board that are connected only when the button has been clicked, showing no resistance in either state. (See photos for two traces/contacts that worked for my builds)
12. Solder the red battery contact wire to one of the contacts you identified on the button board.
13. Solder the red wire from the 2nd JST 1.25 pigtail to the second contact on the button board.
14. If not already present, drill out the desired antenna hole on the new rear enclosure. Insert the SMA pigtail connector and secure with the included nut. The rear of the connector should pressure-fit into the enclosure wall.
15. Insert the battery contacts into the slots on the new rear enclosure, placing the black (spring) contact on the opposite side from the button ole. Use pliers, and bend slightly if the contacts do not seat firmly
16. Reinstall the button board with the gasket into new rear enclosure, using the saved screws to secure.
17. Connect the JST 1.25 pigtails to the solar (JP2/Vsolar) and battery (JP1/Vbat) connectors on the rear of the T114 board
18. Insert the T114 into the enclosure. Press the USB-C connector into the exterior hole and maneuver into the rear clips. Ensure the power cables are routed appropriately (solar to the wall, battery to the button). You can optionally use a small zip-tie to secure the T114 using the loop underneath.
19. Connect the SMA pigtail to the rear of the T114, then attach an antenna to the SMA connector.
20. Connect your computer to the T114 using a USB-C cable, and upload initial firmware following the instructions on the Meshtastic web site.
21. Disconnect the USB-C cable, insert the 18650 battery into the holder, and test the repurposed power button. The LEDs on the T114 will show if it has power or not. If the board does not power on, or the button does not power it off, re-check your connections with a multi meter.
22. Place the new rear enclosure onto the back of the solar panel, taking care to route the solar panel wires to not get pinched. You want the top lip of the enclosure to contact the rubber gasket on the rear of the solar panel. Secure with the 4 screws saved earlier.
23. Power on the node using the power button, and ensure you can connect to it using Bluetooth.
24. Insert the TPU plug into the USB-C port.

Additions

• You can place M6 or 1/4-20 heat set inserts into the holes on the rear of the enclosure. Use a soldering iron or other tool to heat the inserts until they soften the plastic push them into the hole.
• You can add a GPS/GNSS module by attaching the wiring harness to the rear of the T114 before inserting into the case. A small piece of double-sided foam tape can be used to secure the GNSS module to the back of the enclosure.
• If you are not using a GPS/GNSS module, an AirTag can be inserted into the ring next to the T114 holder. Be sure to activate/pair before installing and face the metal side up (allowing for battery changes). A small piece of double-sided foam tape can help keep the AirTag in place. 
• A temperature/humidity sensor can be added by soldering a right angle header or wires to pins 2/3/4/5 to the left of the USB connector (3v3, GND, P.13, P.16). Route the wires to an appropriate location and connect to your sensor board, ensuring the pins are connected properly.

Usage

• Mount/place the node in a location where it should receive sunlight to operate and charge during the day.
• Orient the antenna to have line-of-sight if at all possible to other nodes, and to keep the element vertical. Note that antennas with hinges (like the one pictured) will some amount of reception if bent.
• The button on the back of the enclosure operates as a battery disconnect. With the battery disconnected, the node can be powered from USB or from the solar panel if enough light is shining it. The battery will not charge from the solar panel if disconnected.
• Fully charged, the 1500 mAh 18650 battery included with my lights will last for 2-4 days without sunlight, depending on the amount of wireless traffic in the area.
• While water resistant, this unit is not perfectly sealed from the elements. That being said, I have not had any reliability issues due to moisture intrusion. A desiccant pouch could always be added inside the enclosure if moisture was a concern.