solarpanel.lua

--[[
hi! i spent about four hours writing and
adjusting everything.
at first i thought this would be impossible,
then too easy, then it turned out really difficult.
oh well.

i spent this summer pretty mindlessly,
so this is the first time i put enough comments
into my code to help me think more about what
i'm doing.

cheers to desmos and wolframalpha.

pona tawa sina.
u/Bright-Historian-216
]]
local SAVEFILE = ".solarPanelDeg"
local CTR = "Create_RotationSpeedController_2"
local SWIVEL = "front" -- used for error correction

local c = peripheral.wrap(CTR)
c.setTargetSpeed(0)
local s = peripheral.wrap(SWIVEL)

local function optimalAngle(time)
    --[[
    return 0 at 6:00, 90 at 12:00 and 180 at 18:00.
    at a given time the sun is at
    x: cos(pi(n-6)/12)
    y: sin(pi(n-6)/12)

    using arccos or arcsin a position can be turned
    into an angle;
    arccos(cos(x)) = x
    thus i only need to convert pi(n-6)/12 to degrees
    pi(n-6)/12 * (180/pi) = (n-6)*15 = 15n-90.
    ]]
    return 15*time-90
end
local function saveDeg(d)
    local f = fs.open(SAVEFILE,"w")
    f.write(tostring(d))
    f.close()
end
local function loadDeg(d) -- nil or number
    local f = fs.open(SAVEFILE,"r")
    if f==nil then return nil end
    local n = tonumber(f.readAll())
    f.close()
    return n
end
local swivelError = loadDeg()
local function getActualDeg()
    return -s.getTargetAngle()-swivelError
end
local panelDeg = swivelError
local function moveTowards(angle)
    -- 200 rpm on control = 10 rpm on panel = 60 deg/s
    -- trialed and errored (and errored a lot)
    local rpm = 200
    local sleepTime = (angle-panelDeg)/60
    local degError=1

    if sleepTime<0 then
        sleepTime=-sleepTime
        rpm=-rpm
        degError=-degError
    end

    -- used in the past for predicting error; i wonder if it does anything now?
    local timeError = sleepTime%0.05

    if sleepTime>0.05 then
        c.setTargetSpeed(rpm)
        sleep(sleepTime-timeError)
        c.setTargetSpeed(0)

        panelDeg = getActualDeg()
        panelDeg=panelDeg%360
        saveDeg(swivelError)
    end
end

local function adjustRotation()
    local t = os.time()
    if t>18 or t<6 then return end
    local optimalDeg = optimalAngle(t)
    moveTowards(optimalDeg)
end

local args = {...}
if args[1] == "help" then
    print("solarpanel reset - manually reset known rotation")
    print("solarpanel debug <angle> - measure error")
    print("solarpanel install - set as startup")
    print("solarpanel invert - use if your panels are upside down for whatever reason")
    return
end
if args[1] == "debug" then
    if s==nil then
        print("Place swivel bearing ("..SWIVEL..") and try again")
        return
    end
    print("use reset subcommand after finishing debug")
    panelDeg = 0
    s.disassemble()
    moveTowards(args[2]+0)
    local actualDeg = -s.getTargetAngle()
    print(panelDeg,actualDeg)
    print("error: "..panelDeg-actualDeg.."; "..(actualDeg/panelDeg-1)*100 .."%")
    return
end
if args[1] == "install" then
    if args[2]~="force" and (fs.exists("startup") or fs.exists("startup.lua")) then
        print("You already have a startup script! Use install force to overwrite it.")
        return
    end
    fs.delete("startup")
    fs.delete("startup.lua")
    local f=fs.open("startup","w")
    f.write("print('Starting up solar panels...')\nshell.run('"..shell.resolve("solarpanel").."')")
    f.close()
    return
end
if args[1] == "invert" then
    saveDeg(panelDeg+180)
    return
end
if panelDeg==nil or args[1]=="reset" then
    c.setTargetSpeed(0)
    s.disassemble()

    print("disassemble panel bearing, then enter position number:")
    print("1. facing east (to sunrise)\n2. panel facing up\n3. facing west (to sunset)\n4. facing down")

    panelDeg = (read()-1)*90
    swivelError = -panelDeg
end

while true do
    adjustRotation()
    sleep(0.05)
end