THDB Series - Delay On Break Timer

Littelfuse Time Delay Relays
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The THDB Series combines accurate timing circuitry with high power, solid-state switching. It can switch motors, lamps, and heaters directly without a contactor. You can reduce labor, component cost, and increase reliability with these small, easy-to-use, THDB Series timers.

Operation (Delay-on-Break)
Input voltage must be applied before and during timing. Upon closure of the initiate switch, the output energizes. The time delay begins when the initiate switch is opened. The output remains energized during timing. At the end of the time delay, the output de-energizes. The output energizes if the initiate switch is closed when input voltage is applied.
Reset: Reclosing the initiate switch during timing resets the time delay. Loss of input voltage resets the time delay and output.

Access specifications, certifications, check availability and order parts below

Catalog #Input
Voltage (V)
Storage Temperature (F/C)Time Delay RangeSample CapableCompare
THDB421A120VACNO closed before and during timing-40° to 85°C (-40°F to 185°F)0.1 - 10s externally adjustableNo
THDB434C120VACNO closed before and during timing-40° to 85°C (-40°F to 185°F)1 - 100m onboard adjustableNo