Electric strikes
An electric strike (also called an electromagnetic or electromechanical strike) is a door-frame-mounted device that replaces a conventional fixed strike plate. It holds or releases the door latch or bolt on demand, allowing a door to be opened remotely — by a proximity reader, a keypad encoder, a button, or a control panel — without touching the door handle from the outside.
The door's existing handle, latch, and lock cylinder remain in place. The electric strike simply adds electrically controlled releasing to the door frame. This makes it one of the easiest access control components to retrofit to an existing door.
How an electric strike works
- In the locked state, the strike's keeper (the pivoting jaw) is held firmly in place by a solenoid or motor, trapping the door latch inside the strike body. The door cannot be opened from the outside even with the handle turned.
- When an authorised credential is presented to the reader or keypad, the controller sends a brief electrical pulse to the strike.
- The solenoid releases the keeper, freeing the latch. The user pushes or pulls the door open.
- After the door closes (or after a configured timeout), the solenoid re-engages and the keeper snaps back into the locked position.
Fail-safe vs. fail-secure (NO/NC)
The single most important specification to choose correctly is the fail mode:
| Mode | Also called | Behaviour on power loss | Typical use |
|---|---|---|---|
| Fail-safe | Fail-open, Normally-Open (NO) | Door releases — free egress possible | Fire-escape routes, emergency exits |
| Fail-secure | Fail-locked, Normally-Closed (NC) | Door stays locked | High-security areas, server rooms, vaults |
NO (normally-open) strikes are powered to hold the door locked; cutting power releases the door. This is the fail-safe behaviour.
NC (normally-closed) strikes are powered to release; they require an electrical pulse to open and stay locked without power. This is the fail-secure behaviour.
Local fire and building regulations typically require fail-safe mode on all evacuation routes — check applicable codes before specifying a fail-secure strike on any door that may need to serve as an emergency exit.
Voltage and current
Most HDWR electric strikes operate on 12 V DC. Some models also accept 24 V DC, and a small number support both AC and DC at either voltage. Key points:
- Always match the supply voltage to the strike's specification — operating a 12 V strike on 24 V will damage or destroy it.
- Use a dedicated access control power supply, not a generic wall adapter. Dedicated supplies include short-circuit protection, load regulation suited to the inductive nature of solenoid loads, and often a battery-backup connector.
- The strike draws current only during the release pulse (typically 300–600 ms). Some models have a high-current pick current and a lower hold current; the power supply must handle the peak draw.
Physical dimensions and mortise compatibility
Electric strikes are manufactured in standard sizes that correspond to common strike plate cut-outs. Before ordering, measure:
- The height and width of the existing mortise pocket in the door frame.
- The distance from the door edge to the centre of the bolt or latch.
- The door swing direction (inswing vs. outswing) and whether the door is left-handed or right-handed.
Many HDWR strikes include an adjustable keeper or multiple face plates to accommodate slight size differences.
Electric strikes FAQ
What is an electric strike and how does it differ from an electromagnetic lock?
An electric strike replaces the strike plate in the door frame and works with the existing door latch — the door handle, lock cylinder, and latch bolt all remain. It releases the latch mechanically via a solenoid or motor. An electromagnetic lock (mag-lock) is a different device: it attaches to the door frame and door surface and holds the door shut by magnetic attraction between an electromagnet and an armature plate. Mag-locks hold a heavy door firmly (typically 300–600 kg pull force) but require power to stay locked (always fail-safe). Electric strikes are generally easier to retrofit and work with the existing hardware.
What is the difference between a NO and NC electric strike?
NO (normally-open) means the strike is open (unlocked) when de-energised — you must apply power to lock it. NC (normally-closed) means the strike is closed (locked) when de-energised — you apply power to release it. In practice: a NO strike is fail-safe (power loss = door opens, allowing free exit); an NC strike is fail-secure (power loss = door stays locked). For evacuation routes and fire exits, fire safety codes almost universally require fail-safe behaviour — a NO strike or a fail-safe mag-lock.
How is an electric strike wired into the access control system?
A basic single-door circuit: (1) connect the 12 V DC power supply positive and negative to the strike's power terminals; (2) wire the reader or keypad encoder's relay output (COM and NO terminals) in series with the strike's power line, or connect the relay across the strike's activation input. When the relay closes (on successful authentication), current flows through the strike and it releases. The exit button on the inside of the door is wired in parallel with the relay so pressing it also releases the strike. A door contact sensor can be added to detect if the door is propped open.
In what position does the electric strike lock — when energised or de-energised?
This depends on the model's fail mode. An NC (fail-secure) strike is locked when de-energised and releases only when an electrical pulse is applied — so under normal operation the strike receives a brief pulse to open. A NO (fail-safe) strike is held locked by a continuous current and releases when the current is interrupted by the relay or when power fails. For this reason, NO strikes draw power continuously during the locked state; NC strikes draw power only during the brief release pulse.
What voltage does an electric strike require?
Most HDWR electric strikes are rated for 12 V DC. Some models also accept 24 V DC or support both AC and DC at the rated voltage. Always use the voltage stated on the product label or specification sheet — a 12 V strike connected to 24 V will overheat and fail. Use a dedicated access control power supply rather than a generic adapter: access control supplies are rated for the inductive loads that solenoids present and include overload protection. The power supply must be capable of delivering the strike's peak current during the release pulse.
What size electric strike do I need for my door?
Measure the existing mortise pocket in the door frame (height x width) and the depth of the frame at that point. Standard electric strike sizes align with common architectural hardware cutouts. Also note whether the door swings inward or outward, and the hand of the door (left or right). HDWR electric strikes ship with multiple faceplate options and an adjustable keeper where possible, but the mortise cut-out dimensions must still match within a few millimetres. If you are replacing an existing electric strike, bring the old unit's dimensions or part number when ordering.
Can I use an electric strike on a fire door?
Yes, but only under specific conditions defined by local fire codes and the fire door's certification. The strike must be fail-safe (NO mode) so that the door releases automatically if power is cut during a fire alarm. The strike must not degrade the fire door's certification — use only strikes explicitly listed or tested for use on fire doors. In some jurisdictions, any electric hardware on a fire door must be connected to the building's fire alarm system so that a fire alarm immediately de-energises the strike (and all access control hardware) allowing free evacuation. Consult a qualified fire and life safety engineer before specifying electric strikes on fire doors.
What is the dwell time and how do I adjust it?
Dwell time (also called strike time or release duration) is how long the strike stays released after a successful authentication before it re-locks. Typical values are 1–10 seconds. Dwell time is usually configured on the keypad encoder or access control panel that drives the strike's relay, not on the strike itself. Set it long enough for a person to open the door and pass through but short enough to prevent tailgating. For high-traffic doors, 3–5 seconds is common; for slower users or wide doors, increase to 7–10 seconds.