User:Munin295/Redstone FAQ

Circuit design
Common questions about designing a circuit.

How do I turn a button into a lever?

 * Use a T Flip-Flop.

A button turns on each time it is clicked, while a lever toggles its output each time it is clicked. A T flip-flop is a circuit which toggles its output each time its input turns on, so it can turn the signal from a button into the toggle output of a elver.

How do I turn a lever into a button?

 * Use a Dual Edge Detector.

A lever changes its output when clicked, while a button outputs a pulse when clicked. A dual edge detector is a circuit which outputs a pulse when its input changes (either from off to on, or on to off), so it can change the toggle output of a lever into the pulse of a button.

How do I detect if two or more inputs are on?

 * Use a U2A Decoder.

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Circuit problems
Common questions about diagnosing circuit problems.

Why won't my piston retract?

 * It's still being activated by something else.

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Why won't my circuit turn off?

 * There's a feedback loop somewhere.

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Why does my clock stop working?

 * A torch burnt out.

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 * It's being powered from somewhere.

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Why won't my command block comparator turn off?

 * It needs to be tested again.


 * Command blocks work more like switches than gates. When a command block is activated, it switches its output to reflect the success of its command (on if successful, off if not). So even if you pulse the command block, the output will either just switch or do nothing.


 * You can use a command block pulse limiter (schematics, right) to limit the command block's output to the same pulse length as the input.

What is a redstone comparator used for?
Comparators can take input signals from their back and from their sides, and output to their front (like a repeater). Depending on how they're configured, then can:


 * Maintain signal strength


 * A comparator with no side signals will output the same signal strength as its back input (unlike redstone dust which loses signal strength, or a repeater which always outputs signal strength 15).


 * Compare signal strength


 * If a comparator is in "comparison mode" (front torch down/off, right-click to change), then it will only output its back signal if it's stronger or equal to both side signals – if the back input is weaker, the output shuts off.


 * Subtract signal strength


 * If a comparator is in "subtraction mode" (front torch up/on, right-click to change), then the output will equal its back signal minus the strongest side signal (except the output can't drop below 0).


 * Measure containers


 * A comparator will output a signal strength in proportion to how full a container behind it is (and some other things).

Putting these things together in various ways allows you to make many different kinds of circuits (logic, pulse, clock, memory, etc.).

Comparators are probably most frequently used for their ability to measure containers. Hopper clocks use them to detect when items have finished moving in one direction, item sorters use them to detect when a new item has been filtered out, item elevators use them to detect when an item needs to be moved up, etc.

The other things a comparator can do (maintain, compare, and subtract signal strength) are mostly used in (somewhat advanced) "analog" circuits which perform calculations on signal strength.

How do I build a computer in Minecraft?

 * It's really really complicated.