THDB421A - THDB Series

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Littelfuse Time Delay Relays
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.

Property (Mouseover for details) Value
Input Voltage (V) 120VAC
Input Tolerance (%) ±20%
Input AC Line Frequency (Hz) 50/60Hz
Output Type Solid state
Output Form NO closed before and during timing
Output Load Rating (VA) 6A steady state 60A inrush
Minimum Output Load Current (A) 100mA
Output Voltage Drop (V) ≅2.5V @ rated current
Time Delay Range 0.1 - 10s externally adjustable
Time Delay Tolerance (%) ±1%
Reset Time (ms) ≤150ms
Initiate Time (ms) ≤20ms
Repeat Accuracy (%) ±0.5% or 20ms whichever is greater
Setpoint vs Ambient Temperature and Operating Voltage (%) ≤ ±2%
Open State Leakage Current (A) ≅5mA @ 230VAC
Insulation Resistance ≥100 MΩ
Dielectric Breakdown ≥2000V terminals to mounting surface
Circuitry Encapsulated
Power Consumption ≤2VA
Termination Type 0.25 in. (6.35mm) male quick connect terminals
Mounting Method Surface mount with one #10 (M5 x 0.8) screw
Operating Temperature -40° to 60°C (-40°F to 140°F)
Storage Temperature (F/C) -40° to 85°C (-40°F to 185°F)
Humidity 95% relative non-condensing
Dimensions 2.00 x 2.00 x 1.51 in. (50.8 x 50.8 x 38.4mm)
Weight (lbs/g) ≅3.9oz (111g)
Sample capable No