diff --git a/constructor.lua b/constructor.lua
new file mode 100644
index 0000000..5509027
--- /dev/null
+++ b/constructor.lua
@@ -0,0 +1,138 @@
+function get_element_constructor_formspec()
+    local formspec = {
+        "size[8,9]",
+        "label[2,1;Orb]",
+        "list[context;fuel;2,2;1,1;]",
+        "label[3,1;Source]",
+        "list[context;src;3,2;1,1;]",
+        "label[5,1;Output]",
+        "list[context;dst;5,2;1,1;]",
+        "list[current_player;main;0,5;8,4;]",
+    }
+    return table.concat(formspec, "")
+end
+
+local function can_dig(pos, player)
+    local meta = minetest.get_meta(pos);
+    local inv = meta:get_inventory()
+    return inv:is_empty("fuel") and inv:is_empty("src") and inv:is_empty("dst")
+end
+
+local function on_timer(pos, elapsed)
+    local inv = minetest.get_meta(pos):get_inventory()
+    local update = true
+    while elapsed > 0 and update do
+        update = false
+        local fuel_stack = inv:get_stack("fuel", 1)
+        local src_stack = inv:get_stack("src", 1)
+        local dst_stack = inv:get_stack("dst", 1)
+
+        if not inv:is_empty("fuel") and not inv:is_empty("src") then
+            -- make sure the stack at dst is same as the src
+            if not inv:is_empty("dst") then
+                if not(src_stack:get_name() == dst_stack:get_name()) then
+                    break
+                end
+            end
+            -- make sure orb has enough charge
+            local orb_charge = fuel_stack:get_meta():get_int("stored_charge") or 0
+            -- TODO specific charge required depending on node
+            orb_charge = orb_charge - 1
+            if orb_charge < 0 then
+                break
+            end
+            -- give orb new charge value
+            fuel_stack:get_meta():set_int("stored_charge", orb_charge)
+            inv:set_stack("fuel", 1, fuel_stack)
+            -- "convert" charge into a node at dst
+            if dst_stack:is_empty() then
+                -- create a new stack
+                dst_stack = ItemStack(src_stack:get_name())
+            elseif dst_stack:get_count() >= 64 then
+                -- the max item count is limited to 64
+                break
+            else
+                -- add one node into stack
+                dst_stack:set_count(dst_stack:get_count() + 1)
+            end
+            inv:set_stack("dst", 1, dst_stack)
+            update = true
+        end
+    end
+    minetest.get_node_timer(pos):stop()
+    return false
+end
+
+local function on_construct(pos)
+    local meta = minetest.get_meta(pos)
+    local inv = meta:get_inventory()
+    inv:set_size("fuel", 1)
+    inv:set_size("src", 1)
+    inv:set_size("dst", 1)
+    meta:set_string("formspec", get_element_constructor_formspec())
+    meta:set_string("infotext", "Element Constructor")
+    on_timer(pos, 0)
+end
+
+local function allow_metadata_inventory_put(pos, listname, index, stack, player)
+    if minetest.is_protected(pos, player:get_player_name()) then
+        return 0
+    end
+    local meta = minetest.get_meta(pos)
+    local inv = meta:get_inventory()
+    if listname == "fuel" then
+        if stack:get_name() == "element_exchange:exchange_orb" then
+            return stack:get_count()
+        else
+            return 0
+        end
+    elseif listname == "src" or listname == "dst" then
+        return stack:get_count()
+    end
+end
+
+local function allow_metadata_inventory_move(pos, from_list, from_index, to_list, to_index, count, player)
+    local meta = minetest.get_meta(pos)
+    local inv = meta:get_inventory()
+    local stack = inv:get_stack(from_list, from_index)
+    return allow_metadata_inventory_put(pos, to_list, to_index, stack, player)
+end
+
+local function allow_metadata_inventory_take(pos, listname, index, stack, player)
+    if minetest.is_protected(pos, player:get_player_name()) then
+        return 0
+    end
+    return stack:get_count()
+end
+
+local function on_blast(pos)
+    local drops = {}
+    default.get_inventory_drops(pos, "fuel", drops)
+    default.get_inventory_drops(pos, "src", drops)
+    default.get_inventory_drops(pos, "dst", drops)
+    drops[#drops+1] = "element_exchange:element_constructor"
+    minetest.remove_node(pos)
+    return drops
+end
+
+minetest.register_node("element_exchange:element_constructor", {
+    description = "Element Constructor",
+    groups = {cracky = 2},
+    is_ground_content = false,
+    can_dig=can_dig,
+    on_timer = on_timer,
+    on_construct = on_construct,
+    on_metadata_inventory_move = function(pos)
+        minetest.get_node_timer(pos):start(1.0)
+    end,
+    on_metadata_inventory_put = function(pos)
+        minetest.get_node_timer(pos):start(1.0)
+    end,
+    on_metadata_inventory_take = function(pos)
+        minetest.get_node_timer(pos):start(1.0)
+    end,
+    on_blast = on_blast,
+    allow_metadata_inventory_put = allow_metadata_inventory_put,
+    allow_metadata_inventory_move = allow_metadata_inventory_move,
+    allow_metadata_inventory_take = allow_metadata_inventory_take,
+})
diff --git a/init.lua b/init.lua
index a167ce0..636ba71 100644
--- a/init.lua
+++ b/init.lua
@@ -1,4 +1,5 @@
 local default_path = minetest.get_modpath("element_exchange")
 
+dofile(default_path.."/constructor.lua")
 dofile(default_path.."/deconstructor.lua")
 dofile(default_path.."/orb.lua")