Littelfuse HRDB121 - The HRDB Series combines an electromechanical, relay output with microcontroller timing circuitry. The HRDB offers 12 to 230V operation in five options and factory fixed, external, or onboard adjustable time delays with a repeat accuracy of ±0.5%. The isolated output contact rating allows for direct operation of heavy loads, such as compressors, pumps, blower motors, heaters, etc. The HRDB is ideal for OEM applications where cost is a factor. 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.
Littelfuse

HRDB121

Alternate Item Number: HRDB121

UPC: 079458993769

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Overview

The Littelfuse HRDB121 is a dedicated delay-on-break timer designed for cost-sensitive OEM applications requiring precise timing control. This electromechanical relay integrates microcontroller-based timing circuitry with a 30A SPDT (Single Pole Double Throw) output contact, enabling direct operation of heavy industrial loads such as compressors, pumps, blower motors, and heaters without intermediate relays. The HRDB121 operates on 12VDC input with onboard adjustable time delays from 1 to 100 seconds, offering exceptional repeat accuracy of ±0.5% or 20ms (whichever is greater). Factory calibration tolerance is ±5% for this model, ensuring consistent performance across cycles. The device features a compact, low-cost design ideal for space-constrained installations, with a mechanical life rated at 1 million cycles. Input voltage tolerance for DC operation is -15% to +20%, and power consumption is ≤2W. Accessories such as the P1004-95 Versa-Pot (panel-mount potentiometer) and P1023-6 mounting bracket enable remote adjustment and simplified installation. The delay-on-break operation ensures the output relay energizes upon closure of the initiate switch and remains active throughout the timing period, de-energizing only after the delay completes. Reset functionality is triggered by reclosing the initiate switch during timing or loss of input voltage. With isolated contacts rated for 125/240VAC at 30A (resistive), the HRDB121 delivers reliable performance for industrial control systems where cost and precision are critical. Specifications include a microcontroller-based time delay type, an input voltage of 12VDC with -15% to +20% tolerance, and a power consumption of ≤2W. The output is an isolated SPDT electromechanical relay with general purpose and resistive ratings of 30A at 125/240VAC, 20A at 28VDC, and motor load ratings of 1 hp at 125VAC and 2 hp at 240VAC. Reset time is ≤150ms and initiate time is ≤20ms.
  • Microcontroller-based timing circuitry for precise control
  • Delay-on-break operation with adjustable time delay (1-100s)
  • Isolated 30A SPDT output contacts for direct heavy load operation
  • 12VDC input voltage with -15% to +20% tolerance
  • ±0.5% or 20ms repeat accuracy for reliable performance

Specifications

Brand Name
Littelfuse
Connection Type
Screw Terminal
Current Rating
30 A
Frequency
50/60 Hz
Mounting
Surface mount with one #10 (M5 x 0.8) screw Mount
Mounting Type
Panel-Mount
Number Of Poles
Surface mount with one #10 (M5 x 0.8) screw
Operating Temperature
-40 to 60 F
Operating Temperature, Maximum
60 F
Operating Temperature, Minimum
-40 F
Poles
SPDT
Series
HRDB
Special Features
10Y WARR
Standard
CE/UR/CSA
Sub Brand
SSAC
Voltage Rating
12 VDC
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Frequently Asked Questions about Littelfuse

What certifications and standards do Littelfuse products comply with?

Littelfuse products are certified to multiple international standards, including UL (Underwriters Laboratories), CSA (Canadian Standards Association), CCC (China Compulsory Certification), and EAC (Eurasian Conformity). Customers can verify specific product certifications by consulting individual product datasheets on Littelfuse.com, which provide comprehensive details about standards compliance for each component.

What industries and applications are Littelfuse products used for?

Littelfuse products are critical for electrical protection and safety across multiple industrial sectors, including manufacturing, automation, power distribution, and electrical control systems. Their comprehensive product portfolio serves industries that require robust electrical protection, including motor and pump applications, solar installations, programmable logic controllers (PLCs), electrical switch panels, and critical infrastructure environments. Key product lines protect against overcurrent, voltage transients, ground faults, and temperature-related electrical risks, ensuring equipment safety and operational reliability.

What technical support does Littelfuse offer?

Littelfuse offers comprehensive technical support through multiple channels. Their Technical Hotline (800-TEC-FUSE) provides direct access to engineers who can help identify issues and recommend solutions. Additionally, Littelfuse offers extensive online Technical Resources at Littelfuse.com, including datasheets, product manuals, whitepapers, application guides, and online design tools. Their experienced product and application engineers also provide step-by-step support from design to installation.

What are the main product lines offered by Littelfuse?

Littelfuse offers comprehensive industrial protection and control product lines, including fuses, fuse holders, protection relays, temperature sensors, and electrical safety components. Their key product categories span surge protective devices, custom OEM products, electrical switch panels, medium voltage fuses, ground-fault protection relays, motor and pump protection devices, and temperature sensors. These products are designed to minimize electrical safety hazards, limit equipment damage, improve productivity, and safeguard personnel from electrical faults.

What are the key features of Littelfuse products?

Littelfuse products feature exceptional circuit protection technologies with key characteristics including UL/IEC safety standard compliance, low internal resistance, and advanced protective capabilities across multiple product lines. Their components provide critical protection for industrial systems, offering features like overcurrent protection, voltage transient suppression, and resettable protection devices with ultra-low resistance and compact designs. Key product lines include fuses, metal oxide varistors (MOVs), TVS diodes, PolySwitch devices, and specialized electronic protection components that enhance system reliability and safety.

What environmental ratings do Littelfuse products have?

Littelfuse products feature comprehensive environmental ratings, including NEMA Type 1, 2, 3, 3R, 4/4X, 12, and 13 certifications, as well as IP65 protection. These ratings ensure superior protection in diverse industrial environments, with an operating temperature range of -40°F to +131°F (-40°C to +55°C). Many products also include UV-stabilized materials and neoprene gaskets for enhanced durability in outdoor and challenging conditions.

What accessories are available for Littelfuse products?

Littelfuse offers several key accessories across their product lines, including fuse holders, voltage monitoring modules, and terminal connectors. Specific accessories include the LPSM003ZXID (indicating) and LPSM003Z (non-indicating) POWR-SAFE Dead Front fuse holders for Class CC and Midget-Style fuses, the VRM6048 voltage monitor accessory module, and female quick connect terminals (P1015 series) in various wire gauge sizes. These accessories are designed to enhance protection, monitoring, and connectivity for Littelfuse electrical components.

What is Littelfuse's warranty policy?

Littelfuse provides comprehensive warranty details on their official website at www.littelfuse.com/warranty. Customers should visit this page to review the specific warranty terms and conditions for their specific product lines. For direct warranty support or questions, customers can contact Littelfuse Technical Support at 1-800-TEC-FUSE or email [email protected].

What communication protocols do Littelfuse products support?

Littelfuse supports a comprehensive range of industrial communication protocols, including PROFIBUS, PROFINET, EtherNet/IP, DeviceNet, Modbus RTU, and CANopen. Our products provide flexible connectivity solutions across multiple industrial automation platforms, enabling seamless integration with various control systems and network architectures.

How are Littelfuse products typically installed?

Littelfuse products are typically installed using specialized mounting hardware like fuse holders, blocks, and panels designed for specific industrial applications. The POWR-SAFE Dead Front holders, for example, provide optimum protection for Class CC and Midget-Style fuses, supporting installations up to 600 VAC/DC. Installation often involves using precision terminals with strain relief, such as 0.25 in. female quick connect terminals, to ensure secure and safe electrical connections in industrial control systems.