I share here the pictures of a feeder I've been preparing on late days, maybe they can be useful as source of ideas for who plans to set a Rpi in a remote location without chances of human intervention. It is placed on top of a mountain, in a small shelter hosting other radio equipment, protected from rain or snow. The box is a standard outdoor electric box, waterproof but not submersible (IP55/IP56), dimensions in cm are 19x14x7. Pictures show also the cover. The holes are almost to avoid condensation. On spring or summer, the thermic excursion of the place may be noticeable. The power is supplied by a non-stabilized 13V 600mA power supply (not in pics). There are two 6V 1,3Ah acid lead batteries (series connection) as power backup. The voltage regulation from 12v to 5v is operated by a step-down module, very common in Arduino projects. The chosen model is based on LM2596 chip, output tension can be adjusted by a precision trimmer, max current is about 2,5-3A if heat sink is mounted, anyway I didn't set any. I made an aluminium support where to fix the regulator (lower right corner in the pics) by metallic spacers, it also serves as heat sink. 5V power is directly injected through the 40-pin GPIO header: -white wire=pin2=5v+ -black wire=pin39=ground The red and blue wires (pin 5 and 6) are connected to a push button. The button calls two actions depending on the Rpi status: - If the system is up and working, the button initiates a shutdown sequence (very useful if you don't have any net connection at moment, or simply you're lazy and haven't any will to ssh into Rpi). - If the system is down, it acts as a reset and reboots the Pi. for details about how to implement the functions, read the following link: https://www.stderr.nl/Blog/Hardware/RaspberryPi/PowerButton.html the shutdown button also allows to furtherly extend the functions, eg. remote controlling shutdown/boot by a wireless switch.
Thanks, I'm glad you liked it. It has been working without any trouble since the day it was set on place, actually I felt satisfied enough, so I made a second one. I plan to put the twin on service as soon as the antenna support is ready. Pics show details of the batteries cage and regulator. I've chosen a different model, same chip and performance but with a display, it allows to quickly check input and output tensions. Unfortunately I've found it pretty inaccurate (error is about 0.3V), so my advice is to check always vs an electronic multimeter. The good thing is the error is constant all along the tensions range.
Internet link hasn't been a problem at all, the place is full of TV repeaters and other radio stuff, most of them are monitored and controlled by network, thanks to courtesy of a friend of mine I've just hooked up an ethernet cable and a router in one of their panels. In order to keep in touch with my small box, I've successfully tested the software by https://www.remot3.it it is free and it works flawless with low impact as for memory footprint.
I've been working on a pi powered by solar and using a celluar usb dongle. It seems to pull just under 2000ma, so powering it is easy .. getting a big enough battery to last all night and still be able to charge when it's cloudy has been a challenge.
Nice project, but I guess it wasn't cheap. I would like to see pictures. Did you choose a Li-Po battery? I used gel lead batteries, they're heavy and big, performance hasn't anything to do with Lithium but the good thing is they are cheap and very tolerant as for recharge times and currents, that implies a quite simple recharge circuit also.
Only sealed lead acid batteries for now, the Li-Po are expensive for trying to keep it under a budget for the build. I'm looking for clearance telecom lithium, etc. It's pulling 2000 mA (2A) when you factor in step-down efficiency and a small margin of error. And with lead acid you really only get about 50% of claimed at good voltage, I need at least 24 ah battery for overnight/cloady days then seems solar people typically double it to make up for lead acid issues. That makes it 50 ah, add margin of safety 75-100 Ah and with pricing 100Ah seems the way to go. Also the lead acid needs to be a deep cycle else you will corrode the internals and destroy the battery very fast. $106 100w solar $20 charge controller with USB $100-150 sealed 75-100 ah battery $20 wiring and misc connectors Plus the cost of a PI, SDR, antenna, cell dongle, cell service, etc.
Very interesting experience as for balancing efficiency of the system and costs. What is the nominal voltage for batteries? and for the solar panel ? late switching step-down modules are generally very good as for efficiency but limiting energy losses and heat is a critic point in this kind of applications.
I'm using 12v battery and panel configuration for simplicity since 12 to 5v usb modules are inexpensive, and the cheap solar charge controller I have has 2 USB ports (even better). The controller will do 24V, so I could wire 2 panels with 12 v batteries in series at 24V (they might blow this controller since they put out 19V each at peak sun in Arizona) https://www.amazon.com/gp/product/B06XMY68L6/ I think 12V is pretty easy to work with at the current required by a feeder.
Panel voltage 18-19v peak. Charging at 14.4 - I should turn that down to 13.8 probably. Feeding custom port AZ-Pi-51209 using custom UDP since dongle is 64k but only $20 per year. UDP is required or TCP buffer fills up waiting to send. Antenna is PVC tube 26", not the FA one, range isn't better than 9" PVC one.
13,8V can be too low. Like in car, optimal charge voltage is between 14-14,2V (CV charging, charge current will be limited by voltage difference).
I'm going to check local places for batteries and if no deals then order online this week for 100ah solar. Not sure exactly, but thinking it's going to need to go in a large sealed case with a little venting. with batteries https://www.amazon.com/Seahorse-SE720-Protective-Case-Black/dp/B000OVHAV2/ external battery box https://www.amazon.com/Seahorse-Protective-Case-without-Yellow/dp/B001A1PT8G/ https://www.amazon.com/NOCO-HM300BKS-Snap-Top-Automotive-Batteries/dp/B004W5SFYW/ For the seahorse box, https://www.amazon.com/OdiySurveil-20MM-Aluminium-Diffusion-Cooling/dp/B00UVPT0CS/. Dan built one with a massive aluminum heatsink that handles AZ sun while hanging out the bottom of the box and some carriage bolts for legs so sink is always shaded.
Renology, HQST, $100 for 100W .. all these cheap china panels on amazon are the same https://www.amazon.com/Newpowa-Polycrystalline-Efficiency-Module-Marine/dp/B00L6LZRXM/ https://www.amazon.com/HQST-Watt-Polycrystalline-Solar-Panel/dp/ https://www.amazon.com/Renogy-Monocrystalline-Solar-Panel-Design/dp/B078J42WL7/ I'm going to check out the local solar stores, maybe I can get a dirt cheap array for my house. This seems like a good price. Charge controller and hardware for $150. https://www.amazon.com/dp/B00DCEKKQ0/
That's 0.40 per MB, in a busy airspace that's $400.00 per GB. 1 GB = 1000MB .... That's insane high prices for data. Even their $0.02 per GB is $20/mo. Plus fees. These prices aren't made for feeder units, they are made for devices checking in one an hour or once every 30 minutes with a 10 byte data packet that says "OK, I'm alive". Realistically without destroying your wallet. And unlimited cellular data plan would be less expensive. T-Mobile IoT 64k is $20/year an works well once you use UDP. IoT for companies might want more secure options, but for private feeders not doing anything top secret it is perfect. If you're US based. http://www.embeddedworks.net/wsim4827.html
