As a few of you are aware I have been working on a “green” satnogs station. By green I mean self-sustaining for energy. (Solar / Wind)
So far I have decided to think about this as sort of like a cubesat. As it has a power budget, max size (I am not making a huge thing), and thermal budget (Based on Battery thermal limits).
Firstly I looked at the current draw of my Raspberry Pi during observations and while idle. I found that it draws almost a full amp during observations sometimes more. I also found that just sitting doing nothing but checking in with the network it uses between 200mA and 400 mA. Based off these numbers I decided the based course of action would be to make a system to turn off the Pi when not needed. To keep track of observations and to show the Pi as online an ESP32 was programmed to check the job api and decide if the Pi needed to run.
Secondly I needed to find some form of energy storage. For this I looked online a different battery options. I found that LiFePO batteries were one of the more forgiving types of Lithium batteries. I selected 2 Headway 38120 batteries for my power storage. By connecting them in series with and using a 2S BMS board I will have a voltage supply that varies from 4.0v to about 7.2v with a capacity of 8Ah These batteries have a charging temperature range of -10C to 45C meaning during winter I will have to run a heater for them. It also has a dis-charge temperature of -20C to 65C.
Lastly I decided that I will have a separate arduino (ATmega328 chip on a custom board) running as my power management system. It will watch battery voltage and decide when to cut off the rest of the system and when to run the heaters / charge the battery. For example during winter it will disable charging if the temperature is to low but attempt to run the heater until some low voltage point were the whole system will just shutdown to protect itself with the power management system only waking up now and then to check if it can begin charging.
So far I have the ESP32 code finished and working. I also purchased the batteries and BMS board and also the arduino for the power management board.
I still have to figure out my power generation system and also the heaters. Additionally I still have to decide on the RF side of the whole system.
For power generation I was thinking of using a solar panel facing south and maybe using a vertical wind turbine under the system as part of its support structure.
Anyways I am open to suggestions and criticism.
That sound really nice !
I had the same idea but haven’t done anything yet, I’m really interested into your work, My futur project is to install a station on the top of a mountain, where there is no electricity at all !
I would be interested to know what is the $ budget for an installation like you describe and the life time that you are expecting (I mean even expensive Li-on battery haves a limited “cycles” life time)
Thanks for your informations !
I am also wondering about its life time based around how long it takes the batteries to degrade. Also I have the advantage of having a house with WiFi near by for the internet. If I was going to make this for out in the middle of no where some form of data connection would be needed. Like Cellular or satellite internet. Or maybe even one of the Ham Radio Mesh Networks that exist.
Right now I have spent maybe about $30 on batteries and the BMS. $35 for my existing Pi I am going to use. The ESP32 was I think like $5 and I got 4 ATmega328 for $7.60 from Mouser.
As for the rest I have no idea yet. Sort of just building this for fun. :
So I have good news a new SDR, Filter and LNA have arrived for this project. I also found that my BMS board seems to not be working. So I will have to figure that out.
I am going to start working on the full power system over the next few weeks. (College jsut started back up today for me.)
I will also be setting the SDR up sometime this week to start figuring out the required ppm offset it may need. (And to get my current station up with out using my good SDR that I use to keep in my laptop bag.)
I recently purchased a new BMS board for my batteries. https://www.batteryspace.com/PCM-with-Equilibrium-Function-for-2-cells-6.4V-LiFePO4-Battery-Pack-at-8A.aspx
I think it should work better then the cheap ones from china I was using. (Got like 4 for the price of that one and they didn’t balance the cells.)
Next week I will start to upload my code to gitlab so other can see it. (I will be removing my API key and also WiFi login information from it of course.)
Link to basic code: https://gist.github.com/wgaylord/cf30a021a3592b5e7072bc2374c0e6b9
I finally have the LiFePO4 batteries working correctly. Soon I will try running a station off them. I still need to figure out whats wrong with my antenna to do testing with.
What antenna are you testing with? What issues are you seeing?
Currently I am trying to use my homebrew turnstile. (Use to give good results until I had to move back to using a raspberry pi)
Mostly its just either low signal strength or high noise.
I have never had it working well while using a Pi. Worked very well when I had my x86-64 station working. But that died due to bios corruption on the old hp system. On this old station I did not use an LNA. On the raspberry pi one I have been trying to use on.
I also think maybe my LNA died or is not working right now.