Magnetic Lock Wiring Diagrams: Maglock, Exit Button, Power Supply and Reader

For the dry-contact examples below, the relay is de-energized while locked and energizes to unlock. Supply positive feeds COM, NC feeds the maglock through the required egress-release path, and lock negative returns to supply negative. A PUSH/REX button only requests controller release. The complete door must have the independent release functions required by its approved arrangement, and suppression must follow the lock manual.

Terminal glossary: NO, NC, COM, +12V, GND, PUSH and door status

These are the conventions used in the diagrams. GND means DC negative / 0 V, not protective earth. Terminal names, monitored input circuits and powered-output functions vary: verify the exact manuals before making connections.

Terminal	What it is	Typical connection
+12V / +V	DC positive, 12 V (or 24 V) from the supply; red wire by convention	Controller and reader power; relay COM for the lock feed
GND / − / 0V	DC negative return; black wire by convention	Every device’s negative, including the lock return
COM (dry relay only)	Relay common contact	Lock supply positive; not equivalent to every powered terminal marked COM
NC	Normally closed: connected to COM while the relay is idle	Maglocks and fail-safe bolts
NO	Normally open: connected to COM only while the relay is energized	Fail-secure strikes and bolts
PUSH / REX / EXIT	Request-to-exit input	Illustrated as a NO contact to GND; check required input circuit
SEN / DOOR / DSS	Door-position input	Door-position contact; lock bond / bolt status is a separate function
D0 / D1	Wiegand data lines from a reader	Reader’s green and white wires

A maglock can only be fail-safe: with no current in the coil there is no holding force. It uses NC in these dry-relay examples, with the stated unlock logic. On powered distribution outputs, COM may instead be negative, as on Altronix ACM modules. Electric strikes and bolts come in both versions, and the fail-safe vs fail-secure guide explains how to choose per door.

Many magnetic locks also carry a voltage jumper (12 V or 24 V DC) and a bond-sensor or lock-status output: a dry NO/NC/COM contact that reports whether the armature is fully held. Wire that output to a controller input if you want to know the door is secured, not just closed.

Diagram 1: standalone keypad, maglock and exit button

A standalone keypad has its own user memory and relay, so it can control entry without a separate controller. On an egress door, add the complete approved release arrangement; the REX signal alone is insufficient.

Connect it in this order:

1. Supply +12V to the keypad’s +12V terminal, and supply GND to the keypad’s GND.
2. Jumper +12V to the keypad’s relay COM.
3. Keypad NC through the specified egress-release path to maglock +; maglock − back to supply negative.
4. Exit button’s NO contact between the keypad’s PUSH terminal (sometimes labeled OPEN or EXIT) and GND.
5. Apply only the suppression the exact lock manual specifies, then test every required release path independently of the keypad.

With the relay idle, COM–NC is closed and the lock holds. A valid code or card, or a press of the exit button, energizes the relay for the programmed unlock time; NC opens and the door releases. Check that the keypad’s relay contact rating covers the lock current, especially before adding a second lock. When you compare standalone keypads and exit buttons, check relay ratings, terminal layouts and contact options.

Diagram 2: reader, controller, maglock and power supply

A networked door splits the job: the reader identifies the credential, the controller decides and switches its relay, and the power supply feeds everything.

• Reader: +12V (red), GND (black), D0 (green) and D1 (white) to the controller’s reader port. Most controllers supply reader power from that port. If the reader is powered from elsewhere, its GND must still be tied to the controller’s GND, or the data pulses will not be read reliably.
• Controller: its own +12V and GND from the supply.
• Lock: +12V to relay COM; NC through any release contacts to lock +; lock − to supply GND.
• Exit button: NO contact between PUSH (REX) and GND.
• Door contact: between the door-status input and GND (not drawn).

Run lock power in its own cable where you can. Sharing one multi-conductor cable between lock power and D0/D1 invites the lock’s switching spike into the data lines. A supply with separately fused outputs lets you feed locks and electronics from different outputs, so a shorted lock cable does not take the controller down with it; look for this when comparing access control power supplies.

Diagram 3: interpreting the release path

One possible power-interruption path for a fail-safe lock is:

Battery-backed supply + → dry relay COM → NC → approved release contacts (closed while locked; open to release) → maglock + → maglock − → supply negative

An alternative is the supply’s approved release input switching the relevant lock outputs. A contact’s NC marking describes its de-energized state, not necessarily its healthy or alarm state. Verify the actual contact behavior. Supply interfaces can accept a NC contact, NO contact or specified voltage trigger; never substitute one input type for another.

In the US, sensor-release and door-hardware-release are distinct arrangements. Sensor release can require an approach sensor, an independent labeled manual interruption lasting at least 30 seconds, alarm / sprinkler release and specified power-failure release. Door-hardware release uses the lever or exit device itself to interrupt lock power directly, with separate conditions. An ordinary controller REX input, break-glass device or momentary button alone does not establish either arrangement. Use the adopted code edition and approved release-device instructions to specify the full door.

Where required, alarm and manual release must work with AC absent and the battery connected. Keep logging contacts separate from the power-interruption function. Test sensor or hardware operation, required power failures, release timing and alarm reset / relock behavior before handover.

EN 13637 addresses electrically controlled exit systems in Europe. Any fire-door modification must match the door assembly’s test / certification evidence, including EN 1634-1 where applicable. Listing and system requirements depend on the jurisdiction; UL 294 and UL 1034 are distinct North American standards, not universal proof that an assembled door complies.

Double-door wiring and power-supply sizing

For a pair of doors, fit one lock per leaf (or a double maglock) and wire both in parallel from the same relay output if the leaves must release together. Apply the exact lock manufacturer’s suppression instructions to each lock, and the relay contacts must be rated for the combined current. If they are not, switch the locks through a separate relay module or a power supply output designed for lock switching.

Many dual-voltage locks draw less current at 24 V DC; use their actual ratings rather than assuming an exact half, which also cuts voltage drop on long runs. The lock’s jumper setting and the supply voltage must match.

To size the supply, add up the continuous current of every device at the chosen voltage, taken from each datasheet, then leave headroom; at least 25% is common practice. An example with assumed values: two locks at 0.5 A each, a controller at 0.15 A and two readers at 0.1 A each total 1.35 A. With 25% headroom that is about 1.7 A, so a 2 A load-rated supply covers this operating-load estimate. Check simultaneous peaks, shared charging current and the supply’s limits before selecting 2 A or 3 A. Battery standby adds its own calculation, covered in the power supply sizing guide.

Voltage drop is the other half of sizing. The table shows a 12 V lock drawing 0.5 A at the end of a 30 m (98 ft) cable run, which means 60 m of conductor out and back:

Wire size	Resistance per conductor	Loop resistance, 30 m run	Voltage drop at 0.5 A	Voltage at the lock (12.0 V supply)
22 AWG (0.33 mm²)	52.9 Ω/km	3.17 Ω	1.59 V	10.4 V
20 AWG (0.52 mm²)	33.3 Ω/km	2.00 Ω	1.00 V	11.0 V
18 AWG (0.82 mm²)	20.9 Ω/km	1.25 Ω	0.63 V	11.4 V
16 AWG (1.31 mm²)	13.2 Ω/km	0.79 Ω	0.40 V	11.6 V

Values are illustrative copper conductor resistances at 20 °C; use the selected cable’s specified resistance and installation temperature. Compare the result with the lock’s rated voltage tolerance on its datasheet; lower voltage at the coil means lower holding force.

Wiring an electric drop bolt instead of a maglock

Electric drop bolts use the same terminals, with a few differences:

Lock type	Relay contacts	State on power loss	Typical supply
Maglock	COM + NC	Unlocked	12 or 24 V DC
Drop bolt, fail-safe	COM + NC	Unlocked	12 V DC (some 24 V DC)
Drop bolt, fail-secure	COM + NO	Locked	12 V DC (some 24 V DC)
Electric strike, fail-secure	COM + NO	Locked from outside; inside lever still opens	12 or 24 V, AC or DC by model

• Peak current. A bolt draws more current while it moves than while it holds. Size the supply and cable for the peak figure on the datasheet, and power the bolt from the supply rather than from a controller’s auxiliary output.
• Onboard electronics. Many bolts have a control board with door-position sensing (so the bolt only throws when the door is closed), an adjustable relock delay and a lock-status output. Map door-position and bolt / lock-status outputs to the matching controller inputs; bolt engagement does not necessarily prove that the door is closed.
• Alignment. If the bolt does not line up with its strike plate, it cannot throw fully, and the status output will report the door as unsecured.

When you compare options in the electric bolt locks range, check fail mode, status output and bracket requirements for each door before choosing between a bolt and a maglock.

Suppression: follow the exact lock manual

Inductive loads can produce a switching transient, but lock electronics and suppression differ. Do not add a generic diode or MOV to every maglock. Securitron’s M32/M62/M82B manual explicitly shows a parallel reverse diode as incorrect because it affects quick release. HES specifies a suitable accessory / suppression arrangement for its strikes.

Use the specified component, voltage rating, polarity and location for the exact lock and output. Where a manufacturer calls for a DC flyback diode, its cathode faces positive; reversing it creates a short. A plain diode is not suitable across an AC supply. An arbitrary MOV voltage or a generic 1N4007 recommendation is not a substitute for the equipment instructions.

Troubleshooting: not locking, weak hold, buzzing, residual magnetism

Measure at the lock terminals, under load, before you change anything else.

Symptom	Likely causes	What to check
Never locks	No voltage at the lock; lock on NO instead of NC; fire-alarm input open; exit input held low by a shorted cable or a button wired on its NC contact	DC voltage at the lock; relay state; PUSH and fire-alarm inputs
Never releases	Lock fed straight from the supply, bypassing the relay; relay contacts welded by unsuppressed back-EMF	Relay click and COM–NC continuity when triggered; suppression at the lock
Weak hold	Armature not flat against the lock face; armature fixed rigidly instead of able to pivot; dirt or rust on the faces; low voltage from cable drop; 24 V jumper setting on a 12 V supply	Armature mounting and rubber washers; clean faces; voltage at the lock under load
Buzzing or humming	AC or unsmoothed rectified supply; loose armature; failing supply	Confirm the permitted supply waveform; follow armature mounting instructions without clamping out its pivot
Door sticks briefly after release	Residual magnetism from a worn or missing anti-residual pin or spacer on the armature; debris; slow decay through a suppression diode	Armature anti-residual feature; clean faces; release time
Controller resets or reader glitches when the door releases	Back-EMF; lock power sharing a cable with data; undersized supply	Manufacturer-approved suppression; separate cables; actual peak supply capacity

Pre-power wiring checklist

• Lock voltage setting and permitted supply waveform match the exact model; confirm polarity and tolerance.
• Dry / powered output type, contact rating and unlock logic checked; NC / NO selected from the actual diagram.
• Only manufacturer-approved suppression used; no added diode on a model that prohibits it.
• Every lock returns to supply GND, and the reader’s GND is common with the controller’s GND.
• REX input wiring distinguished from the accepted independent egress-release arrangement.
• Required manual / hardware / sensor and alarm releases tested on mains and battery, including timing and reset behavior.
• Wire gauge chosen for the run length, with voltage at the lock measured under load.
• Lock power and reader data in separate cables where possible.
• Door contact and lock-status output tested at the controller.
• Required locking-system power failures tested; per-circuit fuse / PTC limits followed without increasing fuse ratings to mask overloads.

Next steps

Send your door schedule (lock type and voltage, number of leaves, controller or keypad, and cable lengths) through our request-a-quote form. We confirm that the maglock, exit button, controller and power supply work together before dispatch, quote within 24 hours, and can send samples for a test door.

Sources

• Securitron M32/M62/M82B installation manual, electrical wiring and quick release; M32/M62/M82 instructions: DC isolation, ratings and monitoring.
• HES 1500/1600 installation instructions and SMART Pac III accessory.
• Altronix ACM manual: output terminals, fire-alarm inputs and fuse ratings.
• ICC: electrical egress-locking arrangements; UL: locking configurations.
• BSI: EN 13637 scope; EN 1634 series.