KRDB421 - KRDB Series

Series: KRDB
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Littelfuse products are not designed for, and shall not be used for, any purpose (including, without limitation, automotive, military, aerospace, medical, life-saving, life-sustaining or nuclear facility applications, devices intended for surgical implant into the body, or any other application in which the failure or lack of desired operation of the product may result in personal injury, death, or property damage) other than those expressly set forth in applicable Littelfuse product documentation. Warranties granted by Littelfuse shall be deemed void for products used for any purpose not expressly set forth in applicable Littelfuse documentation. Littelfuse shall not be liable for any claims or damages arising out of products used in applications not expressly intended by Littelfuse as set forth in applicable Littelfuse documentation. The sale and use of Littelfuse products is subject to Littelfuse Terms and Conditions of Sale, unless otherwise agreed by Littelfuse. "Littelfuse" includes Littelfuse, Inc., and all of its affiliate entities.

The KRDB Series is a compact time delay relay measuring only 2 in. (50.8 mm) square. Its microcontroller timing circuit provides excellent repeat accuracy and stability. Encapsulation protects against shock, vibration, and humidity. The KRDB Series is a cost effective approach for OEM applications that require small size, isolation, reliability, and long life.


Operation (Delay-on-Break)
Input voltage must be applied before and during timing. Upon closure of the initiate switch, the output relay 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 will energize 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.

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Product Literature

For Technical Questions

Call +1 800-832-3873 or email us at relays@littelfuse.com 

Property (Mouseover for details) Value
Input Voltage (V) 120 V ac
Input Tolerance (%) -20% - 10%
Input AC Line Frequency (Hz) 50/60
Output Type Isolated relay contacts
Output Form SPDT
Output Load Rating (VA) 10 A resistive @ 125 V ac; 5 A resistive @ 230 V ac and 28 V dc; 1/4 hp @ 125 V ac
Time Delay Type Microcontroller with watchdog circuitry
Time Delay Range 1 - 100 s onboard adjustable
Time Delay Tolerance (%) ±5%
Reset Time (ms) ≤150
Initiate Time (ms) ≤40
Repeat Accuracy (%) ±0.5% or 20 ms whichever is greater
Setpoint vs Ambient Temperature and Operating Voltage (%) ≤±5%
Switching Voltage Maximum (V) 250
Insulation Resistance ≥100
Circuitry Encapsulated
Life Electrical: 1 x 10⁵; Mechanical: 1 x 10⁷
Power Consumption ≤2 VA
Termination Type 0.25 in. (6.35 mm) male quick connect terminals
Mounting Method Surface mount with 1 #10 (M5 x 0.8) screw
Operating Temperature -40° to 60°C (-40° to 140°F)
Storage Temperature (F/C) -40° to 85°C (-40° to 185°F)
Humidity 95% relative : non-condensing
Dimensions 2 H x 2 W in. (50.8 x 50.8 mm)
Weight (lbs/g) 0 Kg
Dimensions 2 H x 2 W in. (50.8 x 50.8 mm)

To request product environmental information, please complete the Product Environmental Information Request Form.