Altronix SMP3ET Selectable Output Power Supply with Battery Backup
The Altronix SMP3ET is a compact power conditioning unit designed for distributed security and access control installations where flexible voltage output and power continuity are non-negotiable. Unlike single-voltage supplies, the SMP3ET lets you select between 6VDC, 12VDC, or 24VDC at 2.5 amperes per output — a practical advantage when integrating devices with different power requirements across a single installation. The unit accepts input from any standard 12–28VAC transformer, making it compatible with legacy and current infrastructure without replacing transformers.
Key Features
- Selectable Output Voltage (6/12/24VDC @ 2.5A): Choose the voltage your downstream devices need without stock-keeping multiple PSU models. Each voltage output supports 2.5 amperes of load — enough for a magnetic lock, electric strike, or multiple smaller loads like card readers and auxiliary circuits.
- Wide Input Range (12–28VAC): Accepts power from transformer outputs commonly found in North American and European panel configurations. This range tolerance means the supply will work reliably even as transformer voltage sags slightly under load or during brownout conditions.
- Integrated Battery Backup: When AC input drops, the SMP3ET automatically switches to battery power. For access control and alarm systems, this means electric strikes, magnetic locks, and alarm circuits stay powered during utility outages — critical for fail-safe operation and code compliance. No separate backup module needed.
- Regulated Output: Internal voltage regulation ensures stable, clean power to sensitive devices like card readers and proximity detectors. Regulatory circuits suppress noise and voltage ripple that can cause nuisance resets or false triggers in low-voltage control circuits.
- Compact Grey Steel Enclosure: Mounts to DIN rail or wall inside electrical cabinets. The enclosure is a standard grey powder-coat finish — not rack-mount or panel-mount. Dimensions and weight are critical for cabinet planning; confirm fit before installation.
- CE Compliance: Meets European electrical safety standards for component-level supplies. If you're deploying in EU-regulated environments or need third-party safety certification, CE marking is a compliance checkpoint.
Integration & Compatibility
The SMP3ET is a standalone power supply — it does not integrate with a control panel, NVR, or VMS directly. It is a component supply that conditions and distributes 12–28VAC input into a selectable DC output with battery backup. Position it in a cabinet alongside your access control panel, alarm receiver, or auxiliary circuits. The 2.5-ampere limit per output means you cannot daisy-chain multiple high-current loads on one voltage rail — size your circuit load carefully and distribute loads across outputs if the supply offers multiple channels.
Battery backup capacity depends on the battery connected to the unit and the load you're running. A small sealed lead-acid battery (12V or 24V nominal, not included) will sustain access control circuits for 15–30 minutes in a power loss — enough for most facilities to switch to generator or utility power. If extended backup is required, confirm battery capacity and charge time with your installer.
When to Choose a Different Model
If your installation requires a single fixed voltage and no battery backup, a passive transformer or unregulated supply may be sufficient — and cheaper. If you need higher output current (above 2.5A per voltage) or integrated monitoring/alarm signaling, consider higher-amperage supplies in the power supply category. If your access control or security system requires UPS-grade power conditioning with extended battery runtime and remote monitoring, a true UPS may be warranted.
Frequently Asked Questions
Q: Does the SMP3ET include a battery?
A: No. The SMP3ET has integrated circuitry to manage battery backup, but the battery itself (typically a 12V or 24V sealed lead-acid or lithium unit) must be purchased and installed separately. Your installer will select a battery capacity based on the load and desired backup runtime.
Q: What's the maximum load per voltage output on the SMP3ET?
A: Each selectable output (6VDC, 12VDC, or 24VDC) supports up to 2.5 amperes. At 24VDC, this is 60 watts; at 12VDC, 30 watts; at 6VDC, 15 watts. Total load across all outputs cannot exceed the supply's capacity, so plan circuit distribution accordingly.
Q: Can I use the SMP3ET with a standard wall transformer?
A: Yes, provided the transformer output is between 12–28VAC. Most North American panel transformers (16VAC or 24VAC) fall within this range. Confirm transformer output voltage before connection.
Q: Is the SMP3ET suitable for CCTV power?
A: The SMP3ET can supply auxiliary circuits in a distributed CCTV installation — for example, powering door sensors, alarm inputs, or low-power PTZ motor feeds. However, it is not a PoE switch or high-current video supply. For main camera power, use purpose-built PoE infrastructure or dedicated camera supplies.
Q: What warranty does the SMP3ET carry?
A: The SMP3ET includes a Lifetime Limited Warranty covering defects in materials and workmanship. Standard warranty exclusions apply (damage from misuse, incorrect installation, or environmental extremes). Confirm warranty terms in the product documentation.
Q: Does the SMP3ET have any remote monitoring or alarm output?
A: The SMP3ET is a basic power supply with battery backup — it does not include network connectivity, remote status signaling, or alarm relay outputs. If you need to monitor power loss or battery depletion remotely, integrate a separate monitoring relay or contact a systems integrator about adding monitoring logic at the panel level.
Ted PerryPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
The Altronix SMP3ET is a workhorse component supply that punches above its modest footprint. The selectable output — 6/12/24VDC at 2.5A per rail — eliminates the need to stock three different single-voltage models, and the 12–28VAC input tolerance means you're not locked into one transformer type. Battery backup is baked in, which is a real operational win for access control and alarm circuits that must stay powered during a mains failure.
Technical Highlights:
- Selectable Output at 2.5A per Voltage: Delivers 60W at 24VDC, 30W at 12VDC, 15W at 6VDC. That's enough for a single electric strike, magnetic lock, or multiple card reader/sensor loads on each rail. Don't attempt to parallel outputs for higher current — each voltage is independently regulated and must be treated as a separate supply.
- Wide 12–28VAC Input Range: Most transformers in the field fall within this window, but brownout conditions or aged transformers may sag. The SMP3ET tolerates that sag, unlike supplies with narrow input windows that can drop offline during utility stress.
- Integrated Battery Management Circuit: The supply automatically disconnects AC and switches to battery when input voltage falls below threshold. This transition is invisible to the load — no momentary dropout. Critical for fail-safe strikes and door locks that must hold position during power loss.
Deployment Considerations:
- Battery Not Included: You must source and install a battery (12V or 24V nominal, typically 4–7Ah sealed lead-acid). Confirm with your integrator that the battery capacity will sustain your circuit load for the desired backup window — usually 15–30 minutes in a typical access control setup.
- Load Segregation Required: With three separate voltage outputs, you have flexibility in mixing 6V, 12V, and 24V loads. However, do not exceed 2.5A per output. If your total load is above 7.5A (2.5A × 3 outputs), this supply is insufficient — specify a higher-amperage unit or split loads across multiple supplies.
The SMP3ET is purpose-built for cabinet-mounted access control and alarm architectures where power backup and voltage flexibility matter. Pair it with a quality sealed battery, wire it cleanly to your transformer input and your control circuits, and it will run unattended for years. Don't waste it on applications that don't need backup — a simpler transformer suffices.
