Wire a QR Gate relay. A Shelly that clicks the door open.
A QR Gate relay is a small Wi-Fi switch — a Shelly — wired to your door strike, your buzz-in button, your access panel or your gate. When a visitor is let in, QR Gate tells it to click for a few seconds and the door releases. Here is the wiring for each kind of door, step by step.
Tested by usOn the bench: a Shelly 1 Gen4 UL with a 12 V DC fail-secure strike.
Relays are new. Today you add them in the dashboard under Park, and a door can use one on QR Gate Parks or the Pro plan. Don't see Relays in your dashboard? Email support@qrgate.app.
Before you start
Five rules for every setup
Low voltage only
Setups 1–6 run on 12 or 24 V. Anything on mains (110–240 V), like setup 7, is a job for a licensed electrician.
Unplug while you wire
Plug in only when every wire is in and checked.
Leaving never depends on QR Gate
Use a fail-secure strike: it only controls the outside. The inside handle or push bar opens with no power, no internet and no QR Gate. Never a magnetic lock.
Follow the maker and your code
Each part's own sheet, and your local code. Whether a door must release on a fire alarm is for your fire marshal or building official.
Fail safe
If the relay can't be reached, visitors get the door's keypad code instead — keep it set on the Door code tab if the door has a keypad.
How it works
From a scan to a click
01
A visitor scans
They scan the door's QR sign and prove their phone number.
→
02
QR Gate decides
It checks the door's rules — hours, members, approval.
→
03
Our relay server
QR Gate sends “click” to mqtt.qrgate.app. Your Shelly keeps one secure connection out to it — nothing on your network is opened up.
→
04
The Shelly clicks
It closes its I–O contact for the click length you set (3 s for a door).
→
05
The door releases
The strike releases, then locks again when the click ends.
One click is two sounds: the strike releases, then locks again when the click ends. Activity shows the entry as “unlock sent”.
UHPPOTE 12 V DC fail-secure, ships with a 1N4007 diode
$21
Power
Facmogu 12 V 3 A DC adapter
$10
Plug to wires
California JOS 5.5 × 2.1 mm female barrel jack to screw terminal
$4
Wire
18 AWG red/black two-wire cable
$9
Lever connectors
Genuine WAGO 221-413 (3-hole) and 221-415 (5-hole)
$12
Total
Setup 1 uses two 3-hole WAGOs and one 5-hole.
~$85
Typical US retail, rounded. Tools: a wire stripper, a small flat screwdriver, and a phone or laptop for the Shelly's settings.
Wire it
Seven setups, one drawing each
01
Our door kit: a 12 V DC strike on a new door
You're fitting a new fail-secure strike, and the Shelly and the strike share one 12 V DC supply. This is the wiring we tested on the bench.
+ (red wire)
− (black wire)
+ only while the relay clicks
Setup 1, as tested: three WAGOs, six short jumpers — four red, two black.Read the drawing as text
Adapter + → WAGO A. WAGO A also takes red jumpers to the Shelly's 12V and I.
Adapter − → WAGO B. WAGO B also takes a black jumper to the Shelly's L, the strike's black wire and the diode's plain end. One hole stays empty.
A red jumper from the Shelly's O → WAGO C. WAGO C also takes the strike's red wire and the diode's striped end.
The Shelly's N and SW stay empty.
You'll need
Shelly 1 Gen4 UL
12 V DC fail-secure strike, with the diode it came with
12 V DC adapter (3 A) and a barrel-jack-to-screw-terminal adapter
WAGO 221: two 3-hole (221-413), one 5-hole (221-415)
18 AWG red/black wire
Wire it
1Unplug everything. Cut six jumpers about 6 in (15 cm) long: four red, two black.
2Strip about 11 mm (just under ½ in) off each end that goes into a WAGO, and about 6 mm (¼ in) off each end that goes into a screw terminal.
3Barrel-jack terminal: a red jumper into +, a black jumper into −. Tighten both.
4WAGO A (3-hole, everything +): the red from the barrel jack's +, a red to the Shelly's 12V, a red to the Shelly's I.
5WAGO B (5-hole, everything −): the black from the barrel jack's −, a black to the Shelly's L, the strike's black wire, the diode's plain end. One hole stays empty.
6WAGO C (3-hole, switched +): a red from the Shelly's O, the strike's red wire, the diode's striped end.
7Tug every wire. Check no bare copper shows outside a terminal, no WAGO holds both a + and a − wire, and the diode's stripe is in WAGO C. Then plug in the adapter and join it to Wi-Fi (below).
Watch out
A WAGO has no + or −: everything in one is joined. Never put a + wire and a − wire in the same WAGO.
The diode's stripe goes toward + (WAGO C). In backwards, it shorts the adapter the moment the relay closes.
N and SW stay empty. N is for mains or 24–48 V DC; SW is a switch input QR Gate doesn't use.
On a real door, not the bench: a 12 V supply with battery backup (Altronix-class) instead of a wall adapter, so the strike and the Shelly stay powered through a short power cut. A metal frame may need a locksmith to cut it for the strike.
Click length on the Lock tab: 3 s
02
A 24 V DC strike
Your strike runs on 24 V DC — or it's a 12/24 V strike you'll run at 24 V.
+ (red wire)
− (black wire)
+ only while the relay clicks
Setup 2: like setup 1, but the Shelly's + goes to its 24–48 V DC terminal, never to 12V.Read the drawing as text
Supply + → WAGO A. WAGO A also takes red jumpers to the Shelly's N (its 24–48 V DC +, per the label) and I.
Supply − → WAGO B, with the Shelly's L, the strike's black wire and the diode's plain end.
The Shelly's O → WAGO C, with the strike's red wire and the diode's striped end.
The Shelly's 12V and SW stay empty.
You'll need
24 V DC supply big enough for the strike (battery-backed on a real door)
24 V DC fail-secure strike (or a 12/24 V one set to 24 V), with its diode
Shelly 1 Gen4 — it also takes 24–48 V DC
Three WAGOs and wire, as in setup 1
Wire it
1If the strike is 12/24 V, set it to 24 V the way its sheet shows (usually a jumper or a switch).
2Wire it like setup 1, with one change: the + jumper from WAGO A goes to the Shelly's 24–48 V DC + terminal, not to 12V.
3On the Shelly 1 Gen4 we tested, the printed label shows 24–48 V DC as L = − and N = +. Follow the label on your own unit — if it shows something else, the label wins.
4The diode is the same as setup 1: stripe toward + (WAGO C).
Watch out
Never put 24 V on the Shelly's 12V terminal.
The strike and the supply must match: a 24 V strike on a 24 V supply.
The same WAGO rules as setup 1: never + and − in one WAGO.
Click length on the Lock tab: 3 s
03
An AC strike (one that buzzes)
Your strike runs on 12 or 24 V AC from a transformer — the kind that buzzes while it's released.
+ 12 V DC to the Shelly
− 12 V DC to the Shelly
AC (no + or −)
AC through the relay
Setup 3: the strike's AC runs through the Shelly's I and O; the Shelly gets its own DC adapter.Read the drawing as text
A separate 12 V DC adapter powers the Shelly: + to 12V, − to L.
One transformer wire → the Shelly's I.
The Shelly's O → one of the strike's wires.
The strike's other wire → the transformer's other wire.
No diode anywhere.
You'll need
The strike's AC transformer, the same voltage as the strike (often already there)
Shelly 1 Gen4
A separate 12 V DC adapter and barrel-jack terminal, for the Shelly
Wire. No diode.
Wire it
1Unplug the transformer and the adapter.
2Power the Shelly from its own 12 V DC adapter: + to 12V, − to L.
3One transformer wire to the Shelly's I.
4The Shelly's O to one of the strike's wires.
5The strike's other wire back to the transformer's second wire. AC has no + or −, so either way round works.
6If the strike's maker calls for a varistor (MOV) across the strike, fit it the way their sheet shows.
Watch out
No diode on an AC strike: a diode on AC shorts it every half-cycle.
The Shelly's 12V terminal takes DC only. Never feed it from the AC transformer — that's why it has its own adapter.
Keep the two supplies apart: nothing from the adapter touches the transformer's wires (separate WAGOs, if you use them).
A buzz while the door is released is normal for an AC strike.
Click length on the Lock tab: 3 s
04
A buzz-in door that already works from a button
A strike is already installed with its own power supply and a desk or reception button that releases it.
New: the Shelly's I and O
Already there — leave it
+ to the Shelly
− to the Shelly
Setup 4: the Shelly is a second button. Either one releases the door.Read the drawing as text
The existing loop stays as it is: power supply → desk button → strike → back to the supply.
The Shelly's I and O go to the button's two terminals, beside the wires already there (in parallel).
Its own 12 V DC adapter powers the Shelly: + to 12V, − to L.
You'll need
Shelly 1 Gen4
A 12 V DC adapter and barrel-jack terminal, for the Shelly
Two wires to the button (or two 3-hole WAGOs to join them)
Wire it
1Switch the door's power supply off. Open the desk button and find its two wires.
2Shelly I to one of the button's terminals, Shelly O to the other — beside the wires already there (in the same screw terminal, or join each pair with a WAGO).
3Power the Shelly from its own 12 V DC adapter: + to 12V, − to L.
4Change nothing else. Switch the door's power back on and press the old button: it still works.
Watch out
Check the button simply switches the strike's power — two wires, to the strike and its supply. If it goes to a panel or an intercom, see setup 5.
If the button's wires carry mains (110–240 V), stop: that's a job for a licensed electrician.
The Shelly's contact is rated 10 A at 30 V DC (15 A at 240 V AC) — far more than a door strike draws.
A DC strike should have a diode across its wires, stripe toward +. Most come with one; if yours has none, add it.
Click length on the Lock tab: 2–3 s
05
An access-control panel with a request-to-exit input
The door is run by an access-control panel (card readers, a keypad) with a request-to-exit (REX) or door-release input.
New: the Shelly's I and O
Already there — leave it
+ to the Shelly
− to the Shelly
Setup 5: the panel itself releases the door, and logs it.Read the drawing as text
The Shelly's I → the panel's REX (or door-release) input; its O → that input's COM / GND.
The existing exit button stays on the same two terminals (in parallel).
The panel's lock wiring is not touched.
Its own 12 V DC adapter powers the Shelly.
You'll need
Shelly 1 Gen4
A 12 V DC adapter and barrel-jack terminal, for the Shelly
Two wires
The panel's manual
Wire it
1In the panel's manual, find a dry-contact input that unlocks the door: REX (request to exit), door release or push to exit. It's usually wired to a button between that input and COM or GND.
2Switch the panel off. Shelly I to that input, Shelly O to its COM / GND — beside the exit button's wires, so both keep working.
3Power the Shelly from its own 12 V DC adapter: + to 12V, − to L.
4Switch the panel on. Once the relay is in QR Gate, Test on its row should make the panel unlock the door for the panel's own unlock time.
Watch out
Some panels can be set so a REX only silences the door alarm without unlocking. Make sure yours unlocks.
Don't wire the Shelly into the lock's power on a panel door — the panel stays in charge of the lock.
The panel logs it as an exit; QR Gate's Activity shows who it was.
A reader input (Wiegand) isn't a dry contact. The Shelly can't use it.
Click length on the Lock tab: 1 s — the panel's own unlock time takes over
06
A motorized gate
A slide or swing gate operator with a wired Open input — the kind a wall button or keypad is wired to.
New: the Shelly's I and O
Already there — leave it
+ to the Shelly
− to the Shelly
Setup 6: a plain contact on Open — no strike, no diode.Read the drawing as text
The Shelly's I → the operator's OPEN input; its O → COM.
Any existing push button or keypad stays on the same two terminals (in parallel).
CLOSE, STOP and the safety inputs are never wired to the Shelly.
Its own 12 V DC adapter powers the Shelly.
You'll need
Shelly 1 Gen4
A 12 V DC adapter, or the operator's accessory power (see step 3)
Two wires
Wi-Fi that reaches the gate
Wire it
1Switch the operator off. In its manual, find the Open input — it may say Open, Full open or Cycle — and its Common (COM).
2Shelly I to Open, Shelly O to COM, beside any push button or keypad already there. It's a plain contact, like a wall button: either way round.
3Power the Shelly from its own 12 V DC adapter. The operator's accessory power is fine only if it's 12 V DC or 24–48 V DC (what the Shelly's label takes) and the operator's manual allows the extra load.
4Before you mount anything, check Wi-Fi at the gate: stand there with a phone. Gate cabinets are often out of reach — a Wi-Fi extender or an outdoor access point may be needed.
5Switch the operator back on.
Watch out
QR Gate only ever triggers Open. Never wire it to Close, Stop or a safety input.
The operator's own photo-eyes, safety edges and auto-close stay in charge (UL 325).
On a Cycle (single-button) input, a click while the gate is moving or open can stop or reverse it on some operators. Use a dedicated Open input when there is one.
LiftMaster and Chamberlain operators sold with myQ still have wired dry-contact inputs — wire to those.
Click length on the Lock tab: 1 s
07
A Shelly powered from mains
There's no low-voltage power where the Shelly goes — only mains (110–240 V AC).
Mains — licensed electrician only
+ low voltage
− low voltage
+ only while the relay clicks
Setup 7: only the Shelly's own power is mains. The strike stays low voltage.Read the drawing as text
Mains → the Shelly's L and N, wired by a licensed electrician as the Shelly's label shows.
The strike stays on its own low-voltage supply: supply + → the Shelly's I; the Shelly's O → the strike's +; the strike's − → the supply's −, with the strike's diode on a DC strike.
The Shelly's 12V and SW stay empty.
You'll need
A licensed electrician
Shelly 1 Gen4 (it takes 110–240 V AC)
The strike's own low-voltage supply
Wire it
1Have a licensed electrician power the Shelly from mains, in a proper box and to your local code.
2The Shelly's I–O contact is separate from its own power, so the strike keeps its own low-voltage supply, wired through I and O as in setups 1–3.
Watch out
Mains wiring is never a do-it-yourself job.
We recommend a low-voltage setup (1–6) instead whenever there's a way to run one.
Every setup · A
Join it to Wi-Fi
1Plug in the power. The Shelly's light blinks red: it's waiting to be set up. The strike stays silent — if it buzzes, or the adapter gets hot, unplug at once (see Troubleshooting).
2On a phone or laptop, join the Shelly's own open Wi-Fi network, named like Shelly1G4-….
3In a browser, open http://192.168.33.1.
4Settings → Wi-Fi: pick your Wi-Fi network — 2.4 GHz only — and type its password. Save.
5It joins your network and gets an address of its own, like 192.168.4.52. Put your phone or laptop back on your Wi-Fi and open that address.
6Prove the wiring: on the home screen, the Output (0) row has a round power button at its far right. Tap it — the strike clicks. Tap it again to switch it back off. Tapping the row's name opens its settings instead; ignore Input (0).
Where to tap. Your Shelly's page looks different; the two rows are what matter.
Every setup · B
Connect it to QR Gate
1In QR Gate: Dashboard → Relays (under Park). Type a name, like “Front door”, and tap Add relay. It shows what to type into the Shelly — keep it open.
2On the Shelly's page: Settings → MQTT. Turn MQTT on and copy in each value exactly. SSL: Default TLS. Tick RPC status notifications over MQTT (and Enable MQTT Control, if your Shelly shows it). Save — it restarts.
3Back in QR Gate, the relay turns Online with its model, like “S1G4 · 1 channel”.
4Lock the Shelly down: Settings → Cloud off, and Settings → Authentication set a password (it's for the Shelly's own page — write it down).
5Tap Test on the relay's row: the strike clicks.
What Add relay shows
Server
mqtt.qrgate.app:8883
Client ID
made for this relay
Username
the same as the Client ID
Password
shown once — copy it now
MQTT prefix
the Client ID again
SSL
Default TLS
Set it up only from its own page, like this. Never in the Shelly app or Shelly Cloud, and never paired as a Zigbee or Matter device — keep it in Wi-Fi mode.
Every setup · C
Put it on a door
1The door's Lock tab → QR Gate relay: pick the relay (and its channel, if it has more than one) and a Click length — 3 s for a door, 1 s for most gates — then Use this relay.
2QR Gate sets that channel to stay off after a power cut, so a power cut never opens the door.
3Scan the door's QR with a phone and verify the number: “You're in. The door is opening.” You hear two clicks — the strike releases, then locks again when the click ends.
4The door's Activity shows the entry as unlock sent.
5Pull the Shelly's power for a moment: the relay reads Offline, then Online again by itself. While it's offline, visitors get the door's keypad code instead.
Don't
What not to wire
Magnetic locks
A maglock holds a door shut with power and can trap people when it fails. QR Gate never uses them: leaving a building must never depend on QR Gate.
Fail-safe strikes on an entrance
They unlock in a power cut, leaving the door open to anyone. Use fail-secure: the inside handle or push bar always lets people out. Whether a door must release on a fire alarm is for your fire marshal or building official.
The Shelly 1PM and other power-metering models
Their contact isn't isolated — it switches the power it measures — so it can't stand in for a button, and it's wrong for a strike.
Anything that holds a door unlocked
No switch on the SW input, no timer, no setting that turns the output on by itself. QR Gate only sends a click that ends on its own, and sets a door's channel to stay off after a power cut.
Other Shelly models
We tested the Shelly 1 Gen4 UL. Another Shelly may work if its label says its contact is potential-free (dry) and it takes 12 V DC or 24–48 V DC — check the wiring diagram printed on it. If it has more than one channel, QR Gate lists each one. Whatever the model, keep it in Wi-Fi mode.
Troubleshooting
If something's off
There's no Shelly network to join
Hold the Shelly's button for about 10 seconds to reset it, then look again. Still nothing? It may be in Zigbee mode — switch it back to Wi-Fi the way Shelly's instructions for your model show.
It won't join my Wi-Fi
Shellys join 2.4 GHz Wi-Fi only. Pick the 2.4 GHz network and check the password.
The strike stays silent when I tap the Shelly's power button
Unplug, then check: the Shelly's O and the strike's red wire share WAGO C; the strike's black wire is in WAGO B (−); the Shelly has power on 12V and L; the diode's stripe is in WAGO C.
The strike buzzes all the time, or the adapter gets hot
Unplug at once. A + wire is in the wrong WAGO, or the diode is in backwards — its stripe belongs in WAGO C.
The relay stays Offline in QR Gate
On the Shelly's Settings → MQTT, check each field matches exactly, SSL is Default TLS, the MQTT prefix is the client ID, and the Shelly is still on Wi-Fi. Lost the password? New password on the relay's row makes a new one — then type it into the Shelly again.
It clicks, but the door doesn't open
A door pressed against the strike can bind it: pull the door shut, then push it open. If that happens often, set a longer Click length on the door's Lock tab, and check the strike lines up with the latch.
After a power cut
It comes back by itself: the relay reads Offline while the power is out, then Online again, and the door stays locked until the next visitor.
Stuck?
Email a photo of your wiring and of the labels on the Shelly and the strike to support@qrgate.app and we'll look at it with you.