How to make 20 minutes (1 day) delay? [duplicate]

Solution 1:

You could accomplish this with 2 hopper clocks chained together.

In 20 minutes there are 24000 game ticks, and an item takes 8 game ticks to transfer from one hopper to another. This means that the wait you want is the same time that it would take 3000 items to transfer.

A single hopper clock only works with up to 320 items, but are able to chain multiple hopper clocks together to multiply the delay:

The second hopper clock can only transfer an item when the first hopper clock activates. If you put 10 items in the first hopper clock like this:

Then 300 items in the second hopper clock:

Then the first hopper clock needs to activate 300 times to activate the second hopper clock and get the output. 300 * 10 = 3000, so the second hopper clock should activate after 20 minutes.

This can all fit within 6*6:

You can stop the clock by keeping powered one hopper in both of the hopper clocks, you should probably turn it on after the dispensers have fired then back off after the trapdoors have opened. You should be able to get the output pulse (it'll be inverted) from the wire on the right.

Solution 2:

Or another option: a despawn clock. Items take exactly 5 minutes to despawn. So you can use 4 droppers and 4 wooden pressure plates as your timer (because 4*5=20, obviously). Each pressure plate is on a block with a redstone torch under it. When the dropper spits an item out, it turns off the torch for exactly 5 minutes, then turns it back on. You can use this to trigger the next dropper in the series. After this occurs 4 times, the last output is your clock output.