Factorio: turn one chest count into a lamp condition
A circuit can begin with one visible question: does this chest contain fewer than a chosen number of plates? Connect a chest to a lamp and use the item signal directly. The small build teaches signal identity, comparison and observation before introducing combinators.
Original explanatory diagram. Read the full method and limitations below.
Choose one item and an illustrative threshold
Put a small amount of iron plate in a practice chest. Choose a threshold such as twenty for the exercise, making clear that it is a learning value rather than an optimal factory buffer. The question is whether the chest’s iron-plate count is below that number. Keep other connected signal sources out of the first build so you can identify where the count comes from without interpreting a larger circuit network.
Connect the entities with circuit wire
Use the circuit connection tool and your configured controls to link the chest and lamp. This connection carries signals; it is different from the electrical supply the lamp needs to operate. Inspect the link and signal information in the game rather than assuming that two nearby entities share data automatically. A powered lamp without the circuit link and a wired lamp without power fail for different reasons.
Configure the lamp’s item comparison
Select the iron-plate signal in the lamp condition and compare it with the chosen threshold. For the example question, use a less-than comparison. Check the symbol and item icon carefully; comparing copper plate or using greater-than would ask another question. You do not need a combinator merely to compare this direct chest count with a constant. Keep the first condition short enough to explain in one ordinary sentence.
Change the count across the boundary
In your own practice build, add or remove plates so the count falls below and then reaches the threshold. Inspect the lamp state and signal value at each point. The equality boundary matters: fewer than twenty differs from twenty or fewer. Record the count and expected condition before observing the lamp. This makes the exercise a clear reasoning task and avoids declaring success merely because the light happened to turn on once.
Illustrative worked example
Illustrative logic: With a condition iron plate less than twenty, a fictional count of nineteen satisfies the comparison, while twenty does not. The player should inspect the lamp’s actual condition and wiring in their own save to verify the behavior. The example supplies arithmetic and a build plan, not a claim of playtesting. A notebook can hold three rows: nineteen, twenty and twenty-one, each with the predicted true-or-false result.
Questions that come up
Does circuit wire power the lamp?
No. Circuit data and electrical power are separate connections in this exercise. The lamp needs an appropriate electrical supply as well as the configured signal condition.
Why does exactly twenty matter?
Because less than and less than or equal ask different questions. Boundary values reveal whether the comparison matches the buffer rule you intended.
References and scope
These sources support the factual background. Examples and exercises are original illustrative teaching material. References do not imply endorsement.
- Official Factorio Wiki: Circuit network — Wired item signals and entity conditions.
- Official Factorio Wiki: Electric system — Electric networks, pole connections and supply coverage.