Storage Lockers

From Asmbly Wiki

This page describes the construction and function of Asmbly's Openpath storage lockers.

Purpose and Requirements

As Asmbly's added specialized portable tools to our inventory, a need was identified to limit access to individuals who've completed requisite training.

Secondary applications might include securing stewards' tools or class supplies, or renting out unused lockers to generate extra revenue. The viability of various applications is highly dependent on how easy it is to manage locker access.

Selected Solution

Asmbly decided to go with Openpath for access control of the lockers. The mechanical design uses off-the-shelf 24V cabinet locks in an overall architecture similar to an Amazon pickup locker bank.

We already know how to update Openpath access groups for individual Neon users programmatically, so automatic management of locker access is an understood expansion to scripts AdminBot is already running. (See the initial implementation)

Theory of Operation

Our locker controller is built around an Openpath Elevator Board. This device provides 16 channels of I/O, supports up to two readers, and critically doesn't have a per-zone monthly subscription cost. With this board we can have up to 16 Openpath access zones for the flat monthly management cost of the board as a whole.

The Elevator Board output channels are configured as Entry/Exit hardware. Each output channel is connected to an illuminated NO pushbutton switch. When you swipe your credential on the lockers reader, the controller closes the output relays for the user's authorized zones. This energizes each channels corresponding pushbutton, lighting it up. Pushing an illuminated button energizes the corresponding electronic lock, opening the locker door.

The Elevator Board input channels are configured as contact sensors and connected to the door sense outputs on the electronic locks, so we can know if doors are forced open or left ajar.

Limitations of the Elevator Board

Use of the elevator board instead of the full-blown 4- or 8-port expansion boards comes with some drawbacks. The relatively low number of supported readers suits our application just fine. The I/O lacks end-of-line supervision, which isn't a problem so long we as keep all our wiring short and local. The biggest issue to be aware of is the small output relays are rated for only 1A rather than the 5A relays on the regular expansion boards. This limits our lock selection unless we add our own intermediate lock-control relays. Additionally, the general-purpose inputs don't work quite the same way as the dedicated contact sensor inputs on the regular expansion boards, requiring pullup resistors for our usecase.

Implementation Details

To make life easier, we decided to get a second Access Control Core instead of running a trunk of wires all the way back to our existing panel. We bought the Elevator Board and ACU loose because we don't love the enclosure of the turnkey Elevator Smart Hub and didn't need the extra reader ports or the UL-listed monitored alarm power supply it includes.

With an ACU, Elevator Board, and our spare (discontinued) low-frequency Smart Reader, we can build a standalone, mobile locker controller that requires only 120V power and network (ethernet or wifi) connections. This lets us rearrange the floorplan in the future without modifying a bunch of facility access control wiring.

Each channel/zone/locker has the same schematic. A single instance is as shown:

Locker channel schematic.png