Redstone Energy Cell Reader

-- use an "Energy Sensor Kit" to right click on a Redstone Energy Cell
-- put the card in a "Nuclear Information Reader"
-- use this program in a computer to read the energy level

-- the Nuclear Information Reader is on the left
m = peripheral.wrap("left")

local sleepTime = 20
local stopEnginePercent = 95
local startEnginePercent = 10

while (true) do
  local current = 0
  local capacity = 0
  local percent = 0
  a,b,c,info = m.get(1)

  -- find the current energy level and max capacity
  for system, status in pairs(info) do
    if system == "energyL" then
      current = status
    else
      if system == "maxStorageL" then
        capacity = status
      end
    end
  end

  if capacity > 0 then
    percent = 100 * current / capacity
    print(tostring(current) .. " / " .. tostring(capacity) .. " (" .. tostring(percent) .. " %)")
  else
    print "Failed to read energy level"
  end

  if percent < startEnginePercent then
    -- turn on the engines
    print("Engines are on")
    redstone.setOutput("right", false)
  else
    if percent > stopEnginePercent then
      -- turn off the engines
      print("Engines are off")
      redstone.setOutput("right", true)
    else
      -- not changing the current state of the engines
      print("Engines continuing in current state")
    end
  end

  sleep(sleepTime)
end