What It Does
Two Shortcuts, one relay, existing gate logic untouched. Clicker stays primary.
02Bill of Materials
About $402 in parts across three vendors, buying two relays ($356 with one). Buy the Pro 2, never the Pro 2PM.
03Wiring
One relay, one enclosure, two dry-contact pairs into the Viking board. Diagram and terminal table.
04Build Steps
Ten steps, paint through grounding, in build order.
05Configuration
Shelly pulse timing, the two API calls, and the two Shortcuts.
06Commissioning & Handover
UL 325 verification, the three-line handover sheet, and the thermal note.
07Decisions
Seven paths considered and rejected, with the one-line reason for each.
What It Does
- Two Apple Shortcuts pinned to the client's iPhone home screen, Open Gate and Close Gate. No new app to learn.
- Each tap closes a relay contact for half a second, which is electrically identical to pressing the Guard Station pushbutton the Viking board already expects.
- Works from anywhere. The Shortcut tries the relay's local IP first and falls back to Shelly Cloud, which is free and has no subscription.
- Nothing about existing gate operation changes. The RF remote, the free-exit loop, the photo beams and edge sensors all continue to work exactly as they do now, and none of them route through any of this.
- The RF clicker remains primary. The phone is convenience. An internet outage means "use the clicker", not "locked out".
- No position feedback in this design. The Reolink camera at the gate is the position feedback.
Bill of Materials
eBay (Digital Bay Tech’s storefront), current US source
New stock is out everywhere. Confirmed out of stock as of 24 Aug 2026: Shelly’s own US store at $84.99, Digital Bay Tech's website for both the new unit and their open-box “Shelly Pro 2 UL” listing at $50.99, and HomeControls.com, which lists the correct SKU SHPRO2ULUS but shows Sold Out. Gabby Electric does not carry Shelly at all.
| Item | Spec | Where | Price |
|---|---|---|---|
| Shelly Pro 2 UL, open box | SHPRO2ULUS, mfg part SPSW-202XE16EU. eBay seller dbtelectronics, Digital Bay Tech’s own storefront, same company. 100% positive feedback, 8 available at time of writing. Listing: “Shelly Pro 2. 2-channels DIN rail smart relay up to 25A Wi-Fi, LAN (Open Box)” | eBay | $46.99 each, $46.52 each buying two |
dbtelectronics is the same company, so those units are very likely the cUL variant and are $4 cheaper. Message the seller to confirm cUL before buying. They hold 100% positive feedback across 335 sales.
Fallbacks, in order, if the eBay open-box units are unavailable or the cUL question can't be resolved.
- Blackwire Designs, 888-316-8921. Their product page explicitly states UL certified, but price and stock are behind a dealer login, so it takes a phone call. Best shot at new-in-box quickly.
- GigaParts, $84.99, accepting backorders, 7 to 14 days. Their page never mentions UL or cUL and their SKU is HA0020, so confirm certification before placing it. Realistically two to three weeks to Montana.
- Skip the UK import. Everything Smart has it in stock at £68.50, but it is the EU board with no cUL, and landed with DHL it runs $100 to $120. That is more than the US new price for less paperwork on a client's gate. What cUL actually buys: listing to US electrical safety standards, which matters for inspection exposure and for any liability or insurance claim if the install ever has an electrical incident.
Amazon
| Item | Spec | Where | Price |
|---|---|---|---|
| QILIPSU enclosure | B08ZRR2DJX, 16.1 x 12.2 x 7.1 in external (410x310x180mm), grey, ABS, IP67, mounting plate and wall brackets included | Amazon | $61.99 |
| 35mm top-hat DIN rail, 12 in | - | Amazon | ~$8 est |
| Breather vent | ZGLUZP M12x1.5, IP68, black, 4-pack (2-pack $4.99); only one is needed, the rest are shop spares. Same thread as the part it replaces, a higher ingress rating, black to match the painted enclosure, and cheaper for four than that part was for one. | Amazon | $6.88 |
| PG9 stainless cable glands, two 3-packs | two used for the Cat6 entries, remainder spare | Amazon | ~$16 est |
| Krylon Fusion All-In-One, gloss black | - | Amazon | ~$10 est |
| Stainless machine screw + nylock nut assortment | M3 to M5, mixed lengths | Amazon | ~$12 est |
| 18 AWG bootlace ferrule kit | assorted sizes | Amazon | ~$13 est |
| Self-adjusting ferrule crimper | IWISS or equivalent, AWG 23-10 | Amazon | ~$22 est |
| Weatherproof padlock | laminated or covered shackle | Amazon | ~$15 est |
| Write-on wire markers / cable label pack | - | Amazon | ~$8 est |
| Aluminum sheet, sun visor | 0.063 in (1/16) 5052, about 18 x 24 in | Amazon | ~$40 est |
| Stainless standoff spacers, sun visor | about 1 in, qty 8 | Amazon | ~$12 est |
Home Depot / local
| Item | Spec | Where | Price |
|---|---|---|---|
| Liquidtight flexible nonmetallic conduit | 1/2 in x 20 ft, 2 straight fittings included, Southwire Ultratite model 59714701 | Home Depot | $28.00 |
| Liquidtight right-angle connector | only if the Viking cabinet entry needs an angled approach rather than straight | Home Depot / local | ~$9 est |
| WAGO 221-2401 lever nuts, 10-pack | - | Home Depot | $9.97 |
| Stainless hex lag screws | 5/16 x 2 in, qty 6, post mount | Home Depot / local | ~$15 est |
| Paint prep consumables | 220-320 grit sanding pad, isopropyl alcohol, painter's tape | Home Depot / local | ~$15 est |
| Silicone or butyl sealant | small tube | Home Depot / local | ~$9 est |
| 18/4 (or two runs of 18/2) CL2 thermostat wire | by the foot, ~$0.25/ft, length site-measured | Home Depot / local | ~$5 placeholder |
Already on hand or already ordered DO NOT REBUY
| Item | Note |
|---|---|
| Cat6 | from the trueCABLE 1000 ft box. Shop-make both short patches, surge protector to switch and switch to Shelly. Buying premade shielded patch cables wastes stock already paid for. |
| Ideal 85-368 shielded feed-thru plugs | with the Ideal FT-45 crimper |
| 8 ft ground rod, acorn clamp, 10 ft #6 bare copper | already on the client's August order, about $45 |
Tools, confirm you own these
- Step bit or unibit up to about 1-3/8 in. Covers the PG9 holes, the M12 breather and the 7/8 in liquidtight holes in one tool.
- Drill/driver
- Caulk gun
- Digital multimeter, for the commissioning continuity checks
Grand total: about $402 buying two relays, or about $356 buying one. Present both; the two-relay figure is the recommendation. About $200 (two relays) or $154 (one) is confirmed against live listings, and the remaining $202 is commodity-hardware estimate.
Every line marked "est" needs a checkout-page confirm before the order goes in, because Amazon blocked automated price extraction.
Confirm on arrival
One thing could not be confirmed from any listing.
- The UACC-ETH-SP-Pro ground lug terminal type, assumed to be a set screw accepting bare #6 copper directly.
Wiring
Enclosure fit, confirmed
| Dimension | |
|---|---|
| Mounting plate (the real mounting area) | 371 x 271 mm, hole spacing 324 x 224 |
| Box interior, overall | 384 x 284 mm |
| Box interior, clear between corner bosses | 359 x 259 mm |
| Corner boss spacing | 329 x 230 mm, 4x M5 |
| Depth | 180 mm external, 166 mm internal, 101 mm base, plate 4 mm thick |
| USW-Flex-Utility footprint | 249 x 218 x 60 mm |
| Free strip beside the Flex-Utility | 122 mm wide x 271 mm tall |
| Shelly Pro 2 | 94 x 19 mm on plate, 69 mm projection |
| Width margin beside the Shelly | 28 mm |
From QILIPSU's dimension drawing, tolerance ±2 mm.
The verdict is that it fits, and the 28 mm margin is the tightest number in the build. The surge protector at 91 x 61 mm stacks below the Shelly in the same strip; together they use roughly 80 mm of the 271 mm of available rail height.
Depth is a non-issue. The Shelly stands about 80 mm off the plate once you count the DIN rail and the 4 mm plate, against 166 mm of internal depth.
The perforated grid area is inset from the plate edges, so plan the Flex-Utility toward one end and expect to drill the solid plate margin for the DIN rail rather than assuming grid holes reach everywhere.
These dimensions are published only as an image inside the Amazon listing's photo carousel, never in text anywhere, which is why they took a manual look to obtain.
Terminal-by-terminal
| Source device | Source terminal | Destination device | Destination terminal | Conductor | Notes |
|---|---|---|---|---|---|
| 120VAC supply | L / N | WAGO lever nuts (in enclosure) | in | 120VAC, 2-conductor + ground | Origin must be confirmed on site, landing blocker |
| WAGO lever nuts | out, leg A | USW-Flex-Utility 60W adapter | AC input | 120VAC | Powers the switch |
| WAGO lever nuts | out, leg B | Shelly Pro 2 | L / N supply | 120VAC | Mains-referenced supply only |
| Loco5AC radio (via INS-3AF-O-G at antenna) | Ethernet out | UACC-ETH-SP-Pro | line side | Cat6 | Uplink to the house. Enters enclosure through PG9 gland |
| UACC-ETH-SP-Pro | protected side | USW-Flex | port 1 | Cat6 | - |
| USW-Flex | port 2 | Reolink RLC-811A | PoE in | Cat6 | PoE. Camera exits enclosure through PG9 gland |
| USW-Flex | port 3 | Shelly Pro 2 | LAN | Cat6 | Data only, short patch. Shelly is mains powered, not PoE |
| Shelly Pro 2 | CH1 output (verify silkscreen) | Viking VFLEX terminal bank | Open | 18/4 conductor | In 1/2in liquidtight conduit |
| Shelly Pro 2 | CH1 output (verify silkscreen) | Viking VFLEX terminal bank | GND | 18/4 conductor | In 1/2in liquidtight conduit |
| Shelly Pro 2 | CH2 output (verify silkscreen) | Viking VFLEX terminal bank | Close | 18/4 conductor | In 1/2in liquidtight conduit |
| Shelly Pro 2 | CH2 output (verify silkscreen) | Viking VFLEX terminal bank | GND | 18/4 conductor | In 1/2in liquidtight conduit |
| 8 ft ground rod | rod | UACC-ETH-SP-Pro | ground lug | #6 bare copper | Bond shield at the grounded end only. Enters enclosure through PG9 gland |
Build Steps
- Paint the enclosure. Scuff 220-320 grit, degrease with isopropyl, shoot Krylon Fusion gloss black, mask the gasket, sealing lip, latches and hinge pins, cure fully before any electronics go in. Painting is the UV fix for ABS, not a cosmetic step, because UV degradation is a surface effect. The sanding pad, isopropyl alcohol and painter's tape are now on the Bill of Materials, not assumed shop stock.
- Mount the DIN rail and the Flex-Utility to the QILIPSU's included mounting plate, confirmed to be a perforated grid plate with through-bolting holes available across the grid area. Flex-Utility toward one end; DIN rail in the 122 mm strip beside it; surge protector below the Shelly, near the uplink cable entry and the ground point. The grid is inset from the plate edges, so expect to drill the solid plate margin for the DIN rail rather than assuming grid holes reach everywhere. The Flex-Utility's own hardware, 4 drywall anchors plus 2 security screws, is wall hardware and wrong for a backplate; use machine screws and nylock nuts instead. The same fastener class covers the DIN rail and the UACC-ETH-SP-Pro, which mounts on 38mm hole spacing, M3/M5, screws not included.
- Drill and fit the enclosure entries. Uplink Cat6 and camera Cat6 each take a PG9 gland. The 18/4 run to the Viking cabinet and the 120VAC supply each take a liquidtight connector, not a gland. Ground conductor takes a gland or a lug through a drilled hole, installer's call. Breather vent: drill 12 mm, not 1/2 in. A 1/2 in bit cuts 12.7 mm, slightly oversize for M12; the O-ring and flange will usually still seal it, but 12 mm is correct. Mount it at the lowest point, facing down or shielded from direct rain impingement. It equalizes pressure so the enclosure does not pump moisture past the gasket on every temperature swing, and it is not meant to take running water head-on.
- Mount the enclosure to the post using the included wall brackets. Drip loop on every cable entering from above.
- Fabricate and fit the sun visor, now that the enclosure is mounted and its orientation to the sun is known. Cut the 0.063 in 5052 aluminum sheet into a top panel and a sun-facing side panel, drill for 8 stainless standoffs at the corners and mid-span, paint gloss black to match the enclosure, and mount with a 2 to 3 in overhang on the top edge and on whichever side catches afternoon sun. The visor is standard on this build, not conditional; the 1 in standoff air gap is what does the cooling.
- Run and terminate the conduit between the enclosures. A 1/2 in liquidtight connector threads into either a spare Viking knockout or a drilled 7/8 in hole with a locknut, so a missing knockout only means a step bit is needed.
- Land the 120VAC with WAGO lever nuts, feeding both the 60W adapter and the Shelly's L and N.
- Land the dry contacts at the Viking end, two conductors on Open and GND, two on Close and GND. At the Shelly, use a spare WAGO 221-2401 from the 10-pack for the shared-common jumper between the two channels' GND terminals, not a twin ferrule. Nothing else in the Viking cabinet changes.
- Patch the Shelly to a spare USW-Flex port.
- Ground rod and bonding.
Configuration
Shelly
- Give it a DHCP reservation on the UDR7 so the LAN address is stable. The LAN-first Shortcut depends on it.
- Both channels: enable
auto_offwithauto_off_delayof 0.5 seconds. This is Shelly's own published value for garage and gate pulse simulation. The setting lives on the device, not in a cloud scene, so it stays correct if a call is duplicated or arrives late. - Both channels default OFF.
- Enable Shelly Cloud.
- Check whether local RPC authentication is enabled. If it is, the LAN Shortcut needs a Basic Auth header. Confirm on site.
- One Shelly Cloud account per client site, Timber SAV holds the login. The Shelly Cloud auth key is ACCOUNT-LEVEL, not per-device, so a leaked key reaches every Shelly on that account. Never share one account across client sites.
The two calls
Local, plain GET, no body. Use id=1 for the Close channel.
http://<gate-shelly-ip>/rpc/Switch.Set?id=0&on=true&toggle_after=1
Cloud, POST with header Content-Type: application/json.
https://<server-shard>/v2/devices/api/set/switch?auth_key=<AUTH_KEY>
{"id":"<device-id>","channel":0,"on":true,"toggle_after":1}
The auth key AND the regional server shard both come from the Shelly app under User Settings, Authorization cloud key, shown on the same screen. The device ID comes from Device, Settings, Device Information.
Apple Shortcuts
Two shortcuts, "Open Gate" and "Close Gate", each pinned to the home screen. Each one: Get Contents of URL against the LAN address first, and on failure fall back to the cloud POST, then show a notification reporting the result.
The notification matters: a fire-and-forget Shortcut that silently fails is the worst outcome for a non-technical client, because his phone has signal and everything else works, so a failure looks like the install broke.
Network
Gate post on its own VLAN. Out to internet allowed. No path to the house LAN in either direction. Verify WPA2/AES is actually enabled on the Loco5AC link at commissioning rather than assuming it; airMAX point-to-point gear commonly ships with encryption off.
Commissioning & Handover
Verify on site
- UL 325. Actuation from out of line of sight is explicitly permitted provided two independent entrapment-protection means are present and functional and every trigger still runs the board's own timing and reversal logic. Wiring across Open/GND and Close/GND is electrically identical to the pushbutton the board expects, so it defeats nothing. What must be verified is that the existing photo beams and edge sensors are landed on the board's MONITORED entrapment inputs, not merely present. That is the single fact that decides compliance and it is a gate-technician check.
- Confirm a momentary Open while the gate is already open does nothing harmful, and that the board's auto-close Timer does not fight a remote Close.
- Confirm WPA2/AES on the radio link.
- Confirm the relay fails open-circuit so loss of power, Ethernet or cloud simply reverts the gate to the RF remote and loops with no stuck input.
Client handover sheet
- The clicker is primary. If the internet is down, use the clicker.
- Always look at the live camera before sending Close. Never send it blind. Entrapment protection covers the gate striking something in its swing; it does not cover a vehicle parked in the swing arc outside beam coverage.
- Here is a spare RF remote.
Thermal note
The Shelly's +40C ceiling is the binding spec in that enclosure; the USW-Flex is good to 55C and its adapter to 60C. A sealed black box in direct sun runs 15 to 30C above ambient, and with the client's enclosure painted black the sun visor is standard on this build, not conditional. It is 0.063 in (1/16) 5052 aluminum sheet, about 18 x 24 in, cut into a top panel plus a sun-facing side panel with cutting margin, stood off about 1 in on 8 stainless standoffs, corners plus mid-span so it does not flutter or sag, and painted gloss black to match the enclosure. It overhangs the box 2 to 3 in on the top edge and on the west or afternoon-sun side, enough to shade through an afternoon at roughly 47.9 degrees north rather than only at solar noon. The 1 in air gap is what does the cooling, not the plate itself. In winter the nested boxes trap the adapter's waste heat, which helps hold the Shelly above its -20C floor.
Commercial rain hoods were considered and rejected. The nVent Hoffman PRH-2013 mounts near-flush and sheds water rather than holding a convective air gap, at $165-197. Hoffman's ARF standoff shield is the correct mechanism but runs $502-613 at this size, scaled for traffic cabinets.
Decisions
| Option considered | Reason rejected |
|---|---|
| Apple Home / HomeKit | Needs a bridge box, because Matter only added a Closures device type in spec 1.5 (Dec 2025) with unproven Apple rendering, and no Shelly SKU has both wired Ethernet and Matter. Would have meant an Apple TV plus a bridge appliance, about $430 and a permanent remote support obligation. |
| Apple-certified garage controllers (Meross, iSmartGate, ratgdo, Tailwind, Konnected) | All Wi-Fi only, all indoor-rated, all built for a single-toggle garage button rather than Viking's separate Open/Stop/Close, and there is no AP at the gate. |
| UniFi UA-Hub-Gate | $305, needs 802.3bt while the gate switch is af/at, and drags a whole access-control platform plus a second app onto the client's phone for one gate and one user. |
| LPR auto-open | The RLC-811A does vehicle detection, not plate reading; real LPR needs a dedicated plate camera plus an NVR or paid OCR, on a driveway that hits canopy at 30 yd. |
| Position feedback from the Viking maglock relay | The Shelly's SW inputs are line-voltage referenced, so reading it would put mains through a low-voltage aux contact. |
| Altelix DIN-rail enclosure at $384.99 | The DIN-rail-branded category carries a large premium; a plain gasketed NEMA 4X box plus $5 of rail is the same result. |
| Cloudflare Worker credential intermediary | Solved a problem that one Shelly account per client site already handles at this scale. |