Always call update_use_power() instead of directly setting the use_power var.

- This will let us react to the change appropriately.
- While we're here, lets define some constants so we can stop using bare numbers.
- Always use those constants when calling update_use_power()

code/modules/power/singularity/particle_accelerator/particle_accelerator.dm

@@ -383,10 +383,10 @@ So, hopefully this is helpful if any more icons are to be added/changed/wonderin
 		if(src.construction_state < 3)//Was taken apart, update state
 			update_state()
 			if(use_power)
-				use_power = 0
+				update_use_power(USE_POWER_OFF)
 		src.construction_state = temp_state
 		if(src.construction_state >= 3)
-			use_power = 1
+			update_use_power(USE_POWER_IDLE)
 		update_icon()
 		return 1
 	return 0

code/modules/power/singularity/particle_accelerator/particle_control.dm

@@ -42,7 +42,7 @@
 
 /obj/machinery/particle_accelerator/control_box/update_state()
 	if(construction_state < 3)
-		update_use_power(0)
+		update_use_power(USE_POWER_OFF)
 		assembled = 0
 		active = 0
 		for(var/obj/structure/particle_accelerator/part in connected_parts)
@@ -52,7 +52,7 @@
 		connected_parts = list()
 		return
 	if(!part_scan())
-		update_use_power(1)
+		update_use_power(USE_POWER_IDLE)
 		active = 0
 		connected_parts = list()
 
@@ -138,9 +138,9 @@
 	..()
 	if(stat & NOPOWER)
 		active = 0
-		update_use_power(0)
+		update_use_power(USE_POWER_OFF)
 	else if(!stat && construction_state == 3)
-		update_use_power(1)
+		update_use_power(USE_POWER_IDLE)
 
 
 /obj/machinery/particle_accelerator/control_box/process()
@@ -212,13 +212,13 @@
 	message_admins("PA Control Computer turned [active ?"ON":"OFF"] by [key_name(usr, usr.client)](<A HREF='?_src_=holder;adminmoreinfo=\ref[usr]'>?</A>) in ([x],[y],[z] - <A HREF='?_src_=holder;adminplayerobservecoodjump=1;X=[x];Y=[y];Z=[z]'>JMP</a>)",0,1)
 	log_game("PACCEL([x],[y],[z]) [key_name(usr)] turned [active?"ON":"OFF"].")
 	if(active)
-		update_use_power(2)
+		update_use_power(USE_POWER_ACTIVE)
 		for(var/obj/structure/particle_accelerator/part in connected_parts)
 			part.strength = src.strength
 			part.powered = 1
 			part.update_icon()
 	else
-		update_use_power(1)
+		update_use_power(USE_POWER_IDLE)
 		for(var/obj/structure/particle_accelerator/part in connected_parts)
 			part.strength = null
 			part.powered = 0