Altronix AL175ULB Dual Output Access Control Power Supply
Overview
The Altronix AL175ULB is a compact board-form power supply and integrated charger designed for multi-zone access control installations where independent voltage outputs are essential. It accepts standard 24/28VAC input and delivers selectable 12VDC or 24VDC output at 1.75A per channel—sufficient for powering card readers, electric strikes, and lock controllers in distributed access control architectures. The unit includes integrated battery charging for sealed lead acid or gel-type backup batteries, supervision monitoring (AC fail, low battery, battery presence detection), and fire alarm disconnect capability for systems requiring emergency integration. UL294 access control certification ensures compliance with applicable safety standards.
Key Features
- Dual Class 2 Power-Limited Outputs: Two independent channels with selectable 12VDC or 24VDC per output. This flexibility eliminates the need for separate 12V and 24V supplies in hybrid installations—configure each channel independently based on the voltage requirements of your readers, locks, and controllers, reducing board count and enclosure real estate.
- 1.75A Maximum per Output: Supports a standard card reader (typically 100–150mA), plus a solenoid strike or mag-lock under normal conditions. For higher current demands across multiple devices per zone, you'll need to parallelize outputs or upgrade to a higher-capacity supply in the Altronix family.
- Integrated Battery Charger: Built-in charger circuit manages sealed lead acid or gel-type backup batteries (sold separately). This is critical for access control backup—when AC fails, the battery keeps readers and locks operational long enough for controlled evacuation or manual override. No external charger module required, saving cost and panel space.
- Supervision Monitoring: The unit reports AC fail, low battery, and battery presence status to your access control system or fire panel. This enables proactive alerts if AC power drops or the backup battery is disconnected—catching installation gaps or maintenance oversights before a real outage occurs.
- Fire Alarm Disconnect Capability: Coordinated shutdown with fire alarm systems. When integrated with a fire panel using the disconnect input, the AL175ULB can de-energize access-controlled doors to allow safe egress during fire events. Essential for life-safety compliance in jurisdictions requiring fail-safe door release on alarm.
- Compact Board Form Factor: At 5.8" × 3.0" × 1.5", this supply mounts directly to DIN rail or embeds into access control panels, eliminating separate enclosure requirements and simplifying wiring. Ideal for retrofit installations or equipment rooms where panel space is scarce.
- Operating Temperature Range 0°C to 49°C: Rated for typical indoor control room and equipment room environments. If your installation spans outdoor or cold storage areas, verify that batteries and connected devices are also rated to the lower limit—the PSU can operate there, but backup batteries and solenoids may have tighter thermal limits.
- Lifetime Limited Warranty: Standard Altronix coverage provides long-term confidence in a mission-critical component. Access control power failures can cascade—this warranty reflects Altronix's expectation that the unit will serve reliably across the life of the system.
Integration & Compatibility
The AL175ULB is protocol-agnostic—it supplies power to any 12VDC or 24VDC access control reader, lock, or controller regardless of technology (Wiegand, OSDP, Clock & Data, or proprietary signaling). Battery presence and AC fail supervision typically integrate via dry relay contacts wired to your access control panel's auxiliary input, or to a fire panel's auxiliary module. Confirm your panel's supervision input voltage and dry relay capacity before wiring. The board is designed for distributed installations where you mount multiple AL175ULB units in a single large panel, each serving a separate zone or building sector—this is far simpler than running long 24VAC and 24VDC distribution cables from a single central supply.
Frequently Asked Questions
Q: Can the AL175ULB supply both 12VDC and 24VDC simultaneously, one on each output channel?
A: Yes. Each of the two outputs is independently selectable (via internal jumpers or field configuration). You can set one to 12VDC and the other to 24VDC, and both will operate in parallel from the same 24/28VAC input. This is the primary value of the dual-output design.
Q: What happens to the backup battery if AC power fails while the system is running?
A: The integrated charger automatically transitions to battery supply mode. The battery maintains the selected 12VDC or 24VDC output voltage to connected devices for as long as the battery capacity permits. The AL175ULB sends a low battery or AC fail signal to your access control system so you can log the event and plan graceful shutdown.
Q: Is the AL175ULB suitable for outdoor installations?
A: The board itself operates from 0°C to 49°C, but it is a bare board-form supply without environmental sealing. You must mount it in a climate-controlled enclosure (NEMA 4X stainless or polycarbonate) if exposed to rain, dust, or temperature extremes. The backup battery will also need environmental protection.
Q: Does the fire alarm disconnect work with all fire alarm systems?
A: The disconnect input accepts a dry contact closure from the fire panel (typically 24VDC or a dry relay output). Your fire panel's outputs and the AL175ULB's disconnect input must be compatible in voltage and current. Consult both manufacturers' wiring diagrams. UL294 certification supports fire/life-safety integration, but the specific fire panel must be tested for interoperability.
Q: What battery types does the AL175ULB support?
A: Sealed lead acid (SLA) or gel-type rechargeable batteries only (sold separately). Lithium or alkaline batteries are not supported—they lack the charging profile compatibility and would be damaged by the charger circuit. Size and amp-hour rating depend on your backup duration requirement (typically 4–24 hours for access control).
Q: How much current can each output safely deliver continuously?
A: 1.75A is the maximum per output. This is sufficient for one solenoid strike (typical 600–1200mA intermittent draw) plus one card reader (100–150mA continuous) under normal operating conditions. If you need to power multiple strikes or high-current mag-locks from one output, you will exceed the rating—parallelize two AL175ULB units or select a higher-capacity supply.
When to Choose a Different Model
The AL175ULB is optimized for dual-zone installations where you need selectable independent output voltages and integrated battery backup in minimal space. If your project requires a single output voltage only, a simpler fixed-output supply may reduce cost. If you need higher current density—such as powering multiple high-draw mag-locks or a bank of readers from one output—consider Altronix supplies in the 2.5A or higher range within their power infrastructure family. If you require UPS-grade battery backup with longer hold-up time or redundancy, evaluate Altronix modular power systems that allow stacking or field battery expansion.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The Altronix AL175ULB cuts through a real pain point in distributed access control: the need to stock and wire two separate 12VDC and 24VDC supplies when a single zone architecture doesn't fit. This compact board form packs dual selectable outputs, integrated SLA charging, and supervision reporting into 5.8 by 3 inches—a footprint that actually fits in retrofit panels without tearing everything apart. The 1.75A per output is honest sizing: it handles a reader and a strike lock cleanly, but won't power a bank of mag-locks without paralleling units.
Technical Highlights:
- Independent 12VDC / 24VDC Output Selection: Eliminates the need for separate supplies and dual transformer runs. Set one channel to 12VDC for readers, the other to 24VDC for your lock controllers—both draw from the same 24/28VAC input. Cuts panel component count and simplifies commissioning troubleshooting.
- Built-in Battery Charger for Sealed Lead Acid / Gel Batteries: No separate charger module. When AC fails, battery seamlessly takes over and the unit reports AC fail / low battery status via dry relay contacts to your access control panel. This closed-loop supervision is your early-warning system for power failures before they cascade into lockouts.
- Fire Alarm Disconnect Dry Contact Input: Integrates with fire panel aux outputs to fail-safe unlock doors on alarm activation—UL294 certified, so you're compliant with life-safety codes. Wiring is straightforward: fire panel contact → AL175ULB disconnect input → solenoid de-energizes.
Deployment Considerations:
- The 1.75A ceiling is real. A typical solenoid strike draws 600–1200mA intermittent, plus a reader at 100–150mA continuous: you're near the limit on one output with a single lock. Multi-door zones require paralleling two AL175ULB units or stepping up to a higher-rated supply. Know your connected load before deployment.
- The board form is naked—mount it in a control enclosure, not freely exposed. If you're installing this in a hallway or parking structure without climate control, the 0–49°C range is a ceiling, and the battery will degrade faster in heat. Verify your site's typical temperature profile before committing to battery backup duration.
- Battery sizing is your responsibility. The charger is built-in, but you specify the SLA or gel battery separately. A 4Ah SLA will hold readers and a single lock for maybe 30–45 minutes; 7Ah extends that to 1–2 hours. Audit your life-safety evacuation time requirements and size the battery accordingly—don't guess.
The AL175ULB is the right fit for modular or phased access control rollouts where you're powering 2–4 reader/lock zones per supply and integrating battery backup and fire coordination from the ground up. It's not a universal power brick—it's engineered for the specific topology of distributed access control, and that focus is why it works so cleanly on DIN rail in cramped enclosures.
