…or what layout is shown in the upper right? I can't quite decode the positions at which the glowstones are placed relative to the spawner.
I have a working xp grinder based around a blaze spawner in Nether. Now I want to build a wither skeleton grinder, but two most convenient crossings are located practically out the door of the blaze grinder chamber. And of course spawning blazes will completely overwhelm the skeleton spawns.
I saw a video with a smart way of toggling the spawner through placing four dispensers with lava buckets on the roof. The four lava streams, when flowing through the spawn area keep it lit enough that no blazes can spawn. But the video glossed over the dispenser locations too, not giving any angles good enough to determine just where they should be. It's almost certainly the layout in the upper right pic, but I really need to be sure – this being survival, I'd rather avoid punching unnecessary holes in a blaze spawner room ceiling.
Best Answer
These pictures look a bit old - on previous versions the spawning area was 8x8x3 centered on the edge of the spawner.
In current versions it is 9x9x3 centered around the center of the spawner. Blazes need light level of 11 or less to be able to spawn. The idea in all of the above pictures is to maintain light level of 12 or more inside the spawning area. The light decreases by one with each block traveled. Glowstone (and lava) are light level 15, the adjacent blocks are light level 14 etc.
Armed with the above, we can now construct the following:
Lava dispensers are at the 4 marked locations and are facing down. The spawner is in the center. Lava will make a plus sign when flowing form a downward-facing dispenser, that is why there is a plus sign of light level 15 and then on the rest of the blocks light level decreases but is still above 11.