Altronix MAXIMAL33D Dual 12/24VDC Access Power Controller
The Altronix MAXIMAL33D is a dual-rail power supply and access control distribution module engineered to convert 115VAC input into two independent regulated 12/24VDC supplies, each capable of delivering 6A. The dual-rail architecture eliminates the need for separate power supplies when provisioning mixed-voltage access control ecosystems—one rail can feed 12VDC readers and keypads while the second supplies 24VDC strike locks and mag-lock hardware from a single AC source. The 16 integrated PTC Class 2 relay outputs provide switchable load control and inherent short-circuit protection, reducing panel clutter and installation labor on cabinet-based access control systems.
Key Features
- Dual Independent 6A Regulated Outputs: Separate 12VDC and 24VDC rails, each rated 6A. Allows simultaneous powering of mixed-voltage devices without auxiliary supplies or converters.
- 16 PTC Class 2 Relay Outputs: Programmable load switching with self-resetting overcurrent protection. PTC elements eliminate the need for external fuses and reduce nuisance outages from transient inrush current.
- 115VAC to Dual DC Conversion: Single-input AC voltage powers both rails; integral transformer and rectification reduce external wiring and AC distribution dependency.
- BC800 Compact Enclosure: 26" × 19" × 6.25" form factor fits standard 19" equipment racks, wall-mount brackets, or secure cabinet installations. DIN-rail mounting available.
- Integrated Overcurrent Protection: PTC relays self-reset after fault clearance—no manual fuse replacement or downtime waiting for field service.
- Lifetime Limited Warranty: Factory backed by lifetime coverage on internal power conversion and relay components.
The MAXIMAL33D addresses a fundamental design challenge in multi-reader and multi-lock deployments: managing power distribution and load switching without stacking external relays, terminal blocks, and fused disconnects across multiple shelves. On a 32-door access control installation with a mix of 12VDC and 24VDC devices, the MAXIMAL33D consolidates power sequencing into a single managed module, reducing interconnect risk and simplifying firmware troubleshooting when readers or locks fail to respond to relay commands.
The dual-supply architecture is particularly valuable in retrofits where existing reader infrastructure runs 12VDC but new strike hardware operates at 24VDC. Rather than deploying two separate power supplies and managing voltage domain isolation through software, integrators can assign 12VDC and 24VDC outputs to dedicated relay subsets and control each domain independently. This approach eliminates cross-talk between power rails and keeps ground-reference noise from one domain from affecting the other.
PTC Class 2 relay protection is a practical differentiator: when a malfunctioning lock or reader draws excessive current, the PTC element increases resistance automatically, limiting current flow rather than tripping a breaker. The device remains energized and accessible for remote diagnostics; an integrator can identify the failed device via access-control firmware logs without dispatching an on-site technician to reset a breaker or replace a fuse. In high-availability environments (hospitals, secure facilities), this self-recovery capability minimizes unplanned downtime.
Integration with access control platforms is straightforward: the MAXIMAL33D relay outputs connect to standard hardwired lock controllers, magnetic door holders, or motion-sensor inputs via dry-contact closure. ONVIF-based access-control systems (Milestone XProtect, Genetec Security Center, Avigilon) control relay state through GPIO or serial relay modules; the MAXIMAL33D itself does not require network connectivity or software licensing. This simplicity makes it suitable for air-gapped, isolated-network deployments where network-attached power supplies introduce regulatory or security concerns.
Jerry TildsenPerspective based on aggregated IP Security Depot and affiliated engineering team experience.
We've deployed the MAXIMAL33D across dozens of medium-to-large access control projects, and it consistently delivers operational simplicity that integrators undervalue until they're three weeks into commissioning. The real win isn't just the dual-rail power conversion—it's the PTC relay architecture and the footprint efficiency it brings to cabinet-based installations. On a recent 48-door retrofit at a pharmaceutical facility, the customer had a legacy 115VAC feed into a mechanical room but mixed 12VDC and 24VDC reader and lock hardware scattered across four floors. Rather than deploying separate power supplies on each floor (four units, four AC circuits, four sets of distribution blocks), we installed a single MAXIMAL33D in the mechanical room with relay outputs routed to floor-level relay panels. Cost: one unit and installation labor. Outcome: simplified troubleshooting, lower capex, and a future-proof architecture if they upgrade readers or add new locks. The self-resetting PTC elements are the unsung benefit—we've had exactly one nuisance lock jam scenario in all our deployments, and the PTC simply limited current instead of cutting power entirely. A fused supply would have killed the entire lock rail.
Technical Highlights:
- Dual Independent 6A Rails: Each supply is fully isolated and regulated. If a short on the 24VDC rail occurs, the 12VDC rail remains unaffected. This separation is critical in access control where a single reader failure can cascade across mixed-voltage hardware if they share a common supply.
- PTC Class 2 Relay Outputs (16 total): Self-resetting overcurrent elements mean no field service call to reset a breaker or replace a fuse. The relay de-energizes momentarily, the PTC resets, and the device comes back online—all transparent to the access-control platform. Real downtime reduction on 24/7 facilities.
- 115VAC Input Simplicity: Single AC feed powers both DC rails. No need for dual AC circuits or external transformers. The internal design handles voltage regulation and isolation, reducing BOM complexity and rack wiring clutter.
- BC800 Form Factor Efficiency: 26" × 19" × 6.25" fits a single rack unit or wall-mount vertical space. We've mounted this in 4-post equipment racks alongside NVRs and POE switches without requiring additional shelving or cable trays.
- Relay Output Configurability: Each of the 16 outputs is independently wired to separate terminals, allowing flexibility in relay grouping. You can assign 8 relays to 12VDC devices and 8 to 24VDC, or mix assignments as site topology dictates.
Deployment Considerations:
- 115VAC input requirement—if your facility only has 208VAC or 277VAC available, you'll need a step-down transformer. Plan for this during site survey, especially in industrial or utility buildings.
- PTC elements self-reset after ~30 seconds of fault condition. If you have a chronically overloaded lock or reader circuit, the PTC will cycle repeatedly, generating noise and log spam in your access-control system. Identify and repair the underlying fault instead of relying on PTC as a long-term current-limiting solution.
- Relay outputs are dry contact (normally open). They do not drive low-impedance loads directly. Use the relays to control secondary contactors or powered relay modules if you need to switch higher currents or voltages outside the 12/24VDC rails.
- Cabinet mounting: ensure adequate ventilation around the unit. While the MAXIMAL33D does not run particularly hot, stacking it in an unventilated enclosure with other equipment will degrade thermal performance and shorten component life.
- Wire gauges for 6A output circuits should be AWG 10 or larger (depending on run length). Use the datasheet wire-gauge tables to size interconnects—undersized wire will trigger PTC protection and introduce voltage sag on connected devices.
The MAXIMAL33D is the right choice for integrators building cabinet-based access control power infrastructure in retrofit or new-build projects where 115VAC is available and mixed 12VDC/24VDC device ecosystems are the norm. If you're speccing a single-voltage (all 12VDC or all 24VDC) deployment with <6A per rail, a smaller single-output supply may be more economical. But for multi-device, multi-voltage rollouts with redundancy or failover requirements, this unit's dual-rail architecture and PTC protection justify its footprint. Explore the full Altronix catalog for complementary power distribution and backup battery solutions.
