Counters

Count events and act on the total. Where a timer triggers on elapsed time, a counter triggers on how many times something happened.

Counting events

A counter does for events what a timer does for time: it watches its input and counts each pulse. When the count reaches a preset value, it turns its output on. It’s how a control circuit acts on "how many" instead of "how long."

How it counts

A counter is edge-triggered — it adds one each time its input goes from off to on (a rising edge), not continuously while the input is held. So a part passing a sensor, a button press, or a machine cycle each adds exactly one to the count. Hold the input on and it still only counts once; it has to release and re-trigger to count again.

• Input: the thing being counted — a limit switch a part trips, a proximity sensor, a push button, or a contact from another part of the circuit.
• Preset: the target count. When the count reaches it, the output energizes.
• Reset: a separate input that clears the count back to zero so you can start again.

Where you use it

• Batching: count 12 parts onto a tray, then stop the conveyor and signal "tray full."
• Packaging: count items into a box, trigger the sealer at the target count.
• Maintenance: count machine cycles and flag service at a threshold.
• Quantity control: run a process exactly N times.

How it works in a circuit

Like a timer or coil, a counter gets a letter, and contacts with that letter follow its output — so when the count hits the preset, those contacts switch and drive the next action (stop the conveyor, light a "full" lamp, start the sealer). Wire something to its reset to clear it and go again.

What to take away

A counter counts rising edges of its input and energizes its letter when the count reaches the preset; a reset clears it. Use it when the trigger is a quantity of events rather than elapsed time. With timers and counters, your control circuits can react to time and count — the basis of real sequencing and batching.