Altronix RBUL Ultra-Sensitive Relay Module 12/24VDC
The Altronix RBUL is a compact relay module engineered for 12/24VDC control circuits where power efficiency and minimal wiring load are critical. Operating at just 30mA, the RBUL eliminates the current draw overhead of conventional relays, making it ideal for remote activation in access control, alarm signaling, and gate/strike control applications. Its single SPDT output switches up to 1A @ 28VDC—sufficient for most low-voltage access control coils, solenoid gates, and auxiliary alarm circuits. Selectable voltage input means a single module works in 12VDC or 24VDC installations without stock complexity.
Key Features
- Selectable Input Voltage: 12VDC or 24VDC operation. Single SKU eliminates inventory overhead across mixed-voltage sites and simplifies spare-parts management.
- Ultra-Low Operating Current: 30mA draw. Reduces power supply sizing, minimizes downstream wiring gauge requirements, and lowers total system power consumption on extended runs.
- Single SPDT Output Contact: One normally-open and one normally-closed contact per relay. Supports both energize-to-activate and fail-safe deactivation logic without a second relay.
- 1A @ 28VDC Switching Capacity: Rated for access control strikes, solenoid gates, and alarm sirens. Over-current protection via host circuit breaker or module-level fusing recommended for inductive loads.
- Compact Form Factor: DIN-rail or surface-mount installation. Minimal footprint in crowded control cabinet or remote junction box.
- Lifetime Warranty: Manufacturer warranty covers defective relay coil and contacts under normal operating conditions.
Access control systems increasingly rely on distributed relay logic at door readers, gate controllers, and alarm nodes. The RBUL's 30mA operating current is a material advantage when daisy-chaining multiple relays on a single PoE-sourced 12VDC loop or when powering remote door strikes from a shared access panel. Unlike larger industrial relays that draw 50–100mA, the RBUL reduces the gauge and cost of 18-pair or 22-pair control cabling running across parking lots or fence lines. SPDT switching allows direct integration with both fail-secure and fail-safe strike configurations without requiring separate latching logic.
The module pairs directly with Altronix power supplies (ACM, AP, UPS, and POWER-SERIES) and works in any 12/24VDC alarm or access control topology. Typical wiring: low-voltage signal from a door reader, alarm sensor, or motion detector triggers the RBUL coil; the relay contact then closes to energize a strike, gate solenoid, siren, or indicator lamp. No external interface, no firmware—pure relay hardwired logic, ideal for environments where network uptime cannot be guaranteed or where legacy hardwired control must coexist with IP cameras and readers.
Integration is straightforward: the RBUL terminal block accepts 18–22 AWG wire. DIN-rail mounting or surface-mount brackets fit standard electrical enclosures. One-time wiring, no commissioning beyond a continuity check. Suitable for outdoor or indoor installations; enclosure IP rating depends on cabinet selection, not the module itself. For high-inductive-load circuits (solenoid gates, large access strikes), pair the RBUL with a surge-suppression diode or MOV across the load to extend relay contact life.
Marty AllisonPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've deployed the Altronix RBUL across a range of access control retrofits and stand-alone alarm circuits where power efficiency is non-negotiable. The 30mA operating current is not a marketing talking point—it's a real constraint reliever. On a 200-door campus with readers hardwired back to a central access panel via twisted-pair, that sub-40mA-per-door allowance means you can run eight to ten relays off a single 24VDC 3A supply without voltage sag or nuisance resets. Compare that to a bulkier industrial relay at 80mA, and you're potentially upsizing two power supplies per building. We've also found the SPDT contact invaluable for fail-safe strike scenarios—you get both NO and NC paths in a single relay, eliminating the need to spec a second module or a latching relay for gates that must drop power on alarm. The selectable voltage input eliminates a common source of on-site field errors: integrators inadvertently installing a 12VDC-only module in a 24VDC cabinet, or vice versa.
Technical Highlights:
- 30mA Ultra-Low Operating Current: Standard industrial relays draw 50–150mA coil current; the RBUL hits 30mA, materially reducing supply-sizing requirements and voltage drop across long control cable runs. On a four-wire pair from a distant reader to a central panel, that lower current budget preserves signal integrity and allows smaller-gauge wiring without sag. A tangible capex win on larger deployments.
- SPDT Contact Topology: Single relay provides both NO and NC contacts. Enables fail-safe strike circuits without a dual-relay configuration. Integrators often spec a second relay unnecessarily; the RBUL collapses that BOM item.
- Selectable 12/24VDC: One part number works across mixed-voltage sites. Reduces inventory overhead, lowers spare-parts cost, and eliminates field-installed jumper confusion. We've seen this catch mistakes at 2 a.m. on a Monday.
- 1A @ 28VDC Maximum Switching: Covers most solenoid strikes, gate operators under 24W, and siren circuits. Over-current loads (large 24VDC gate motors, high-draw solenoids) require a separate contactor or MOSFET driver; know your load before installation.
Deployment Considerations:
- Inductive Load Protection: Solenoid coils and relay windings generate back-EMF spikes on de-energization. Always install a suppression diode (1N4007 or equivalent) across the relay output if switching inductive loads. Omitting this detail will shorten contact life from years to months and risk nuisance coil failures.
- Wiring Gauge on Extended Runs: Although the RBUL's 30mA draw is low, a 300-foot control cable from panel to a distant remote reader introduces ~4–6Ω of loop resistance on 22 AWG. At 30mA, that's ~0.12V drop—usually acceptable, but verify voltage at the module input on site before sealing the cabinet.
- Terminal Block Torque: Altronix terminal blocks are rated 18–22 AWG wire. Over-torquing or under-torquing can result in intermittent contact. Use a 0.5Nm (inch-pound) screwdriver on barrier-block fasteners; don't force it.
- Ambient Temperature: The RBUL is rated 0–50°C operating range. Outdoor cabinets in direct sun or unheated spaces may exceed this; verify cabinet thermal management or consider a heated enclosure for winter installations.
- Load Testing on Commissioning: Always trigger the relay with a continuity tester or short-circuit the coil input while monitoring the output contact closure. A no-click or slow click indicates coil contamination or poor connection; investigate before power-cycling the entire circuit.
The RBUL is the right choice for access control integrators and alarm installers who need low-power, deterministic relay logic and minimal footprint. For applications requiring networked intelligence, conditional logic, or analytics, look at a programmatic access controller instead. For straightforward door-strike or siren activation in a low-voltage hardwired environment, the RBUL is proven, efficient, and field-proven across thousands of installations. See the Altronix catalog for compatible power supplies and modular control components.
