Plain Lua: switched PSU protection script

[zicht]

Hi,

All electronic skill persons know a switched psu needs a "cool" down to drain internal accumulated power BEFORE switching on again. Otherwise you risk to burn your electronics. (many psu like examples can be found)

This is a universal solution for that, its a replacement for commandArray for this device :

Code: Select all

-- ============================================================
--  Protection system (toggle‑protection for power supplies)
--  Stored in RAM‑drive: Z:\temp\protect_state.json
-- ============================================================
protect = {}   -- global so all scripts can use it
local PROTECT_DEFAULT = 10  -- seconds
local PROTECT_FILE = "Z:\\temp\\protect_state.json"
-- Load protection state from JSON
local function protect_load()
    local f = io.open(PROTECT_FILE, "r")
    if not f then return {} end
    local content = f:read("*a")
    f:close()
    if content == "" then return {} end
    return json.decode(content)
end
-- Save protection state to JSON
local function protect_save(tbl)
    local f = io.open(PROTECT_FILE, "w")
    if not f then return end
    f:write(json.encode(tbl))
    f:close()
end
-- Main function: safeSet(device, action, seconds)
function protect.safeSet(device, action, seconds)
    local now = os.time()
    local protect_time = seconds or PROTECT_DEFAULT
    local key = "protect_until_" .. device
    -- Load current state
    local st = protect_load()
    local protect_until = st[key] or 0
    -- OFF → always execute + start protection window
    if action == "Off" then
        st[key] = now + protect_time
        protect_save(st)
        commandArray[device] = "Off"
        print("safeSet: OFF executed, protection active for "..device)
        return
    end
    -- ON → block or execute
    if action == "On" then
        if now < protect_until then
            print("safeSet: ON blocked for "..device.." (protection active)")
            return
        end
        -- Protection expired → execute ON
        cArray[device] = "On"
        print("safeSet: ON executed for "..device)
        return
    end
    -- Any other action → pass through
    commandArray[device] = action
end

usage :

Code: Select all

protect.safeSet("Device", "Off", X)
protect.safeSet("Device", "On")

what it does :
At the off command it writes a json (can be a uservar if you prefer that = easy to change, but i noticed the json write to my rammdrive is much faster compaired to uservar setting) The json written contains a safety window starttimer (UNIX time)
When a script tries to switch the device on, it will check if its allready allowed to switch on. If not it ignores the command.

This can be a constrain --> it is no longer a switch on command and forget : you need to keep running protect.safeSet("Device", "On") untill its safetytimer has expired. So you need to think about this in your flow design in lua.

NOTICE : in order to make it work as expected all commandArray for this device should be replaced by protect.safeSet() !
Any commandArray="On" will completely overide the protection window and possible break your psu

Use at your own risk ! Electronics break easy : so think twice, do once --> Please test with a dummy device before putting in production...
My coding skills are very limited, so there can be errors inside ( for me it works at this moment)