HRDS321 - HRDS Series

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Littelfuse Single Shot Relays
The HRDS Series combines an electromechanical relay output with microcontroller timing circuitry. It offers 12 to 230V operation in five options and factory fixed, onboard or external adjustable time delays with a repeat accuracy of ±0.5%. The output contact rating allows for direct operation of heavy loads, such as compressors, pumps, blower motors, heaters, etc. This series is ideal for OEM applications where cost is a factor.


Operation (Single Shot)
Input voltage must be applied before and during timing. Upon momentary or maintained closure of the initiate switch, the output relay energizes for a measured interval of time. At the end of the delay, the output de-energizes. Opening or reclosing the initiate switch during timing has no affect on the time delay. The output will energize if the initiate switch is closed when input voltage is applied.
Reset: Reset occurs when the time delay is complete and the initiate switch is opened. Loss of input voltage resets the time delay and output.

Property (Mouseover for details) Value
Input Voltage (V) 24VDC
Input Tolerance (%) -15% - 20%
Output Type Electromechanical relay
Output Form Non-isolated SPDT
Output Load Rating (VA) General Purpose: SPDT-NO: 125/240VAC ≅ 30A; SPDT-NC≅15A; Resistive: SPDT-NO≅30A for 125/240VAC 20A for 28VDC; SPDT-NC≅15A for 125/240VAC 10A for 28VDC; Motor Load: SPDT-NO≅1 hp for 125VAC 2hp for 240VAC; SPDT-NC≅1/4hp for 125VAC 1hp for 240VAC
Time Delay Type Microcontroller circuitry
Time Delay Range 1 - 100s onboard adjustable
Time Delay Tolerance (%) ±5%
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%
Surge Protection IEEE C62.41-1991 Level A
Insulation Resistance ≥100 MΩ
Dielectric Breakdown ≥2000V RMS terminals to mounting surface
Circuitry Encapsulated
Polarity DC units are reverse polarity protected
Life Mechanical - 1 x 106; Electrical - 1 x 105 3 x 104 for 1hp 6 000 for 1/4hp 1hp and 2hp
Power Consumption ≤2W
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 3.00 x 2.00 x 1.50 in. (76.7 x 51.3 x 38.1mm)
Weight (lbs/g) ≅3.9oz (111g)
Sample capable No