Object Detector, cleanup and different behaviour:

* Name to scan for can be specified by right-clicking it
* It can receive digiline signals that change the name to scan for
* A sign above it for the name doesn't work anymore (this features wasn't used often anyway)

mesecons_detector/init.lua

 -- Object detector
--- Detects all entities in a certain radius
+-- Detects players in a certain radius
 -- The radius can be specified in mesecons/settings.lua
 
+local object_detector_make_formspec = function (pos)
+	local meta = minetest.env:get_meta(pos)
+	meta:set_string("formspec", "size[9,2.5]" ..
+		"field[0.3,  0;9,2;scanname;Name of player to scan for (empty for any):;${scanname}]"..
+		"field[0.3,1.5;4,2;digiline_channel;Digiline Channel (optional):;${digiline_channel}]")
+end
+
+local object_detector_on_receive_fields = function (pos, formname, fields)
+	local meta = minetest.env:get_meta(pos)
+	meta:set_string("scanname", fields.scanname)
+	meta:set_string("digiline_channel", fields.digiline_channel)
+	object_detector_make_formspec(pos)
+end
+
+-- returns true if player was found, false if not
+local object_detector_scan = function (pos)
+	local objs = minetest.env:get_objects_inside_radius(pos, OBJECT_DETECTOR_RADIUS)
+	for k, obj in pairs(objs) do
+		local isname = obj:get_player_name() -- "" is returned if it is not a player; "" ~= nil!
+		local scanname = minetest.env:get_meta(pos):get_string("scanname")
+		if (isname == scanname and isname ~= "") or (isname  ~= "" and scanname == "") then -- player with scanname found or not scanname specified
+			return true
+		end
+	end
+	return false
+end
+
+-- set player name when receiving a digiline signal on a specific channel
+object_detector_digiline = {
+	effector = {
+		action = function (pos, node, channel, msg)
+			local meta = minetest.env:get_meta(pos)
+			local active_channel = meta:get_string("digiline_channel")
+			if channel == active_channel then
+				meta:set_string("scanname", msg)
+				object_detector_make_formspec(pos)
+			end
+		end,
+	}
+}
+
 minetest.register_node("mesecons_detector:object_detector_off", {
 	tiles = {"default_steel_block.png", "default_steel_block.png", "jeija_object_detector_off.png", "jeija_object_detector_off.png", "jeija_object_detector_off.png", "jeija_object_detector_off.png"},
 	paramtype = "light",
@@ -10,7 +51,10 @@ minetest.register_node("mesecons_detector:object_detector_off", {
 	description="Player Detector",
 	mesecons = {receptor = {
 		state = mesecon.state.off
-	}}
+	}},
+	on_construct = object_detector_make_formspec,
+	on_receive_fields = object_detector_on_receive_fields,
+	digiline = object_detector_digiline
 })
 
 minetest.register_node("mesecons_detector:object_detector_on", {
@@ -21,7 +65,10 @@ minetest.register_node("mesecons_detector:object_detector_on", {
 	drop = 'mesecons_detector:object_detector_off',
 	mesecons = {receptor = {
 		state = mesecon.state.on
-	}}
+	}},
+	on_construct = object_detector_make_formspec,
+	on_receive_fields = object_detector_on_receive_fields,
+	digiline = object_detector_digiline
 })
 
 minetest.register_craft({
@@ -37,19 +84,10 @@ minetest.register_abm(
 	{nodenames = {"mesecons_detector:object_detector_off"},
 	interval = 1.0,
 	chance = 1,
-	action = function(pos, node, active_object_count, active_object_count_wider)
-		local objs = minetest.env:get_objects_inside_radius(pos, OBJECT_DETECTOR_RADIUS)
-		for k, obj in pairs(objs) do
-			if obj:get_entity_name()~="mesecons_pistons:piston_pusher_sticky" and obj:get_entity_name()~="mesecons_pistons:piston_pusher_normal" and obj:get_player_name()~=nil then
-				if minetest.env:get_node({x=pos.x, y=pos.y-1, z=pos.z}).name=="default:sign_wall" then
-					if obj:get_player_name()~=minetest.env:get_meta({x=pos.x, y=pos.y-1, z=pos.z}):get_string("text") then
-						return
-					end
-				end
-				local objpos=obj:getpos()
-				minetest.env:add_node(pos, {name="mesecons_detector:object_detector_on"})
-				mesecon:receptor_on(pos)
-			end
+	action = function(pos)
+		if object_detector_scan(pos) then
+			mesecon:swap_node(pos, "mesecons_detector:object_detector_on")
+			mesecon:receptor_on(pos)
 		end
 	end,
 })
@@ -58,24 +96,9 @@ minetest.register_abm(
 	{nodenames = {"mesecons_detector:object_detector_on"},
 	interval = 1.0,
 	chance = 1,
-	action = function(pos, node, active_object_count, active_object_count_wider)
-		local objs = minetest.env:get_objects_inside_radius(pos, OBJECT_DETECTOR_RADIUS)
-		local objectfound=0
-		for k, obj in pairs(objs) do
-			if obj:get_entity_name()~="mesecons_pistons:piston_pusher_sticky" and obj:get_entity_name()~="mesecons_pistons:piston_pusher_normal" and obj~=nil 
-			and obj:get_player_name()~=nil then
-				if minetest.env:get_node({x=pos.x, y=pos.y-1, z=pos.z}).name=="default:sign_wall" then
-					if minetest.env:get_meta({x=pos.x, y=pos.y-1, z=pos.z}):get_string("text")== obj:get_player_name() then
-						objectfound=objectfound+1
-					end
-				else
--- Detected object is not piston pusher - will be changed if every entity has a type (like entity_type=mob)
-					objectfound=objectfound + 1
-				end
-			end
-		end
-		if objectfound==0 then
-			minetest.env:add_node(pos, {name="mesecons_detector:object_detector_off"})
+	action = function(pos)
+		if not object_detector_scan(pos) then
+			mesecon:swap_node(pos, "mesecons_detector:object_detector_off")
 			mesecon:receptor_off(pos)
 		end
 	end,