Revisiting the Harbor Breeze Build
The meshtastic website has a tutorial to repurpose a Harbor Breeze Solar Light into a meshtastic radio, written by Tavis Gustafson. The guide is great, but in my attempt to build this, I found there are a few additions and tweaks that aren’t listed in the original article but are quite useful. This post is an attempt to capture my notes in a single place for others to reference.
The goal is not to rewrite the guide and the assumption is that you’ve read the original tutorial.
I by no means claim this is the best way to do this. I’m just documenting my own iterations on the original post.
Equipment
In my build, I used the following equipment:
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The original light - $10 from Lowe’s
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Gorilla Waterproof caulk & seal - $8 at your local hardware store
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Drill with 1/4" drill bit [optional]
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Soldering Iron
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RAK Wireless RAK1901 Temperature and Humidity Sensor $9 from Rokland [optional]
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Generic JST PH 2.0 connectors - $10 [optional] note black and red polarity is swapped here
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E-Z LOK Threaded Insert for Plastic Tapered Single Vane Brass Thread Inserts 1/4-20 Pack of 50 - $10 [optional] for use if you want to use a game camera or any other 1/4-20 mount with a 3d print (either drill a hole or remix a print).
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Trail Camera Mounting Bracket，Hunting Pro Gear Acccessery, Wildlife Cam Holder Deer Monitor Stand Hunter Camera Kit -$22 [optional]
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CoolFilm looks really interesting and apparently it is used in Austin mesh, but I don’t know where to buy it: https://www.heatinverse.com/coolfilm
Cool 3d prints
The Rak Mount was already linked to in the original article, but plugging it here. A photo of the mount in use:
Also here is a dovetail that can screw into things
N Connector Prints:
I’ve tried my hand at modifying this second one to add a heat inset. It is available here - I tried to edit it with some open source tools and bambu studio had to repair it. This version is the repaired version. This works with the heat insets I linked to above.
Using the Button
Buried in the photos of one of the remixes is a reference about how you can modify some resistors to use the battery protection feature. There’s also a screenshot from discord included.
Further Research
Before doing more, I wanted to understand what was happening.
A close-up of the solar board IC shows it is a YX8183. It’s a solar powered LED charger integrated circuit and I found a translation of the spec sheet here.
Of note, it looks like it can go up to 300mA on the LED circuit. I bet this could power a raspberry pi 0.
The Q1 transistor looks like its label is A1SHB. It’s a p-channel MOSFET. Data sheet here - it performs like a light switch and turns the LED on and off based on the value it reads from the IC.
R3, R8, and R4 (103) are 10k ohm resistors.
R2 (R560) is a 0.56 ohm resistor.
R1 (3R3) is a 3.3 ohm resistor.
Make the changes
Based on reading the spec sheet, it is correct that removing R6 will disable the on/off feature in the IC and keep the LED in the “on” state. This resistor feeds power from the solar panel back to the IC. When the sun is out, it shows voltage and turns off the light. When it is removed, there is no power so it thinks it is night.
From here, I think you could just solder directly into the LED +/- to your board. However, I couldn’t account for the impact of R1 here so I wired directly into the mosfet output for my + and onto the board for my LED -.
Take note that my JST connector colors are reversed, so my red goes to negative (-) and my black goes to positive (+).
See photos for view of how my board looked:
Cooling Concerns
I put the temperature sensor on my board and monitored how hot it got. In my tests, I had one build with no cooling attempts, and tried various other techniques, such as passive cooling with aluminum foil, copper foil, with small vents through flexible straws, and even a smal 20mm x 20mm fan wired to the solar panel. In my comparisons in upper 90* (F) in direct sunlight, the highest reading I had was 138, but the cooling attempts did not make any difference in temperature in my builds.
I also discussed with some folks in the Austin mesh who said they have had no fires or issues in the Texas heat with the solar lights, so I am less worried about the heat.
I did find that panel orientation matters, and nodes perpendicular to the horizon got the least hot, while parallel with the horizon got the most hot.
I also tried the variant with the IAQ monitor and some venting via flexible straws, but even with the 20mm fans, I would get very high readings even on clear days with great air quality. These builds are not ideal for air quality monitoring.
Game Camera Mount
Using the 3d print I referenced earlier and the heat inset screws I linked in the resources, I put this together so I could use compatible screw mounts like those that are used with game cameras or other camera tripods.
Dead trees can be useful mounts for meshtastic radios. Straps can choke the tree, so if the tree is dead that is not a concern. There won’t be foilage to block sunlight.
An example of my test builds below:
Other Build Photos
Future Work
I’d like to investigate the feasibility of using this build with a bigger battery, a raspberry pi 0, and a small camera replacing the LED. Some early tests suggest the pi 0 W 2 can run over wifi with ssh active and camera streaming over SSH and use under 200mah in power (closer to 100mah in idle).
The panels provide at least 400mah in direct sunlight, so it’s possible the pi could run on a 5000mah battery and still top off in direct sunlight.
Some possible use cases:
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relay between two frequency offsets
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wilderness monitor that can send alerts on bluetooth beacons, wifi beacons, movement on camera, or sound
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lightning sensor