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Device guide / Circuits
05

Timer relay circuits

Two common uses of a timer relay: a delayed start with on-delay, and a stair light with off-delay.

LNS11314KT1A1A2KT11518H1
On-delay: S1 controls the coil of KT1, and H1 comes on through contact 15–18 of KT1 after the delay.
LNKT1A1A2S11314S21314KT1 B1KT11518H1
Off-delay with a control input: the supply A1–A2 of KT1 is on all the time, and push-buttons S1 and S2 control the B1 input.

How it works

LNS1KT1KT1H11On-delay: S1 turned to I

The coil of KT1 is energised and the time starts running. H1 is still off.

LNS1KT1KT1H12Time elapsed

Contact 15–18 closes and H1 comes on.

LNKT1S1S2KT1 B1KT1H13Off-delay: S1 pressed

B1 is energised. Contact 15–18 closes at once and H1 comes on.

LNKT1S1S2KT1 B1KT1H14Button released

B1 loses its voltage and the delay starts. H1 stays on until the time has elapsed.

The contact of a timer relay changes state after a delay. The type of delay is chosen by whether something has to happen later or keep going for a while longer.

On-delay

When the coil is energised, the time starts running. When the time has elapsed, contact 15–18 closes and 15–16 opens. When the coil is de-energised, the contact returns at once. Typical uses are a delayed start, a start-up warning and the changeover time in star-delta starting.

Off-delay with a control input

The timer relay has a permanent supply on A1–A2 and is controlled from the B1 input. When B1 is energised, the contact changes over at once. When B1 loses its voltage, the time starts running, and the contact returns when the time has elapsed. Stair lights and fan run-on are done this way, for example.

Remember

  • An off-delay timer relay with a B1 control input needs a permanent supply. If the supply is lost, the contact returns at once.
  • On multifunction timer relays the function is selected with a switch. Check the function and the terminal numbers in the manufacturer's instructions.

Sources

  1. Finder: 80 series timer relays, function descriptions