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I've got a basic chicken farm, which takes eggs from a bunch of seed chickens, and channels them down to a dispenser. The dispenser has a comparator coming out the back which checks whether it's full, then it starts a comparator clock, which fires the dispenser until it's empty. It works great, until the dispenser gets full, then it stops working for some reason. Any ideas on how I can modify this so it'll always work?

The pictures below should illustrate my setup. If you imagine the third picture is a still frame: all the eggs are in the dispenser and nothing is happening. The comparator isn't turning on or off.

enter image description here enter image description here enter image description here

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I didn't know comparators could work like that - last I checked, a comparator in "read inventory mode" couldn't also do subtractions or comparisons. Maybe it's changed. – immibis Jan 8 at 7:16
up vote 7 down vote accepted

When the dispenser is full, the comparator is getting a signal strength of 15 from the dispenser. The signal from the repeater that it leads into is giving at most a signal of power 12 to the side of the comparator:

enter image description here

As 15 > 12, the comparator remains on.

To fix this, you should have the repeater lead into a comparator clock, rather than using the same comparator to detect the items in the dispenser and act as a clock. E.G:

enter image description here

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Well, that clock certainly trumps the one I was going to suggest. For the longest time I've been using a hopper-powered clock, but this fires much faster (and probably causes less hopper-related lag)! If you'll excuse me I have a lot of redstone to reconfigure. – Trent Hawkins Jan 8 at 1:01
    
Thanks a lot! I'll try it out in the morning, and accept the answer when I get it working :). – Leo King Jan 8 at 1:08
    
My favorite clock method. Been using it for so long I forget. – ydobonebi Jan 8 at 1:10
    
@colorfusion he basically just combined the two comparators in your design into one but he didn't turn it to subtract mode. – ModDL Jan 8 at 2:34
    
I'm so very glad this was a helpful answer, but as a non-Minecraft person, this entire post reminded me of this: youtube.com/watch?v=xq0XNILIYTw – Kyle Hale Jan 8 at 4:01

This technique is based on a comparator clock. In your case you have not set the comparator to subtract mode. if you right click on the comparator the torch on the front will turn on and your clock will work.

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Switching the comparator mode alone doesn't quite solve the problem, it will fire once and then freeze again. The problem remains somewhat the same, as the comparator's A input (The dispenser when full - 15) is still higher than the side B input (12), and the circuit will just stay in the on position (flicking the switch would cause the cause the circuit to fire once). To get this method working you'd also need another repeater replacing the wire labeled "13" in colorfusion's answer. – Trent Hawkins Jan 8 at 3:28

You should set the both repeaters to 2 ticks and the comparator to subtracting mode. this is because the comparator cant keep up with your one tick repeaters because a comparator uses one tick for cauculating it's output

Just right click both repeaters one time as well as the comparator. this should fix the problem for 1.8.8. (i don't know if it works in the snapshot)

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