KY-05 display case alarm


The KY-05 is an electronic alarm/lock designed to guard shop display cases, rooms, and similar locations. Legitimate users gain access by holding their validated electronic key to a metal contact. This will disable the alarm and optionally power a relay, allowing the user to open the display case. If the case is opened without a valid key, the alarm will sound and will keep sounding until a valid key is held to the contact. It is possible to attach a 'Sesame button'; pressing this button has the same effect as holding a valid key to the contact when pressed.


The KY-05 will usually be in the 'Guard' state. If the door is opened in this state, the alarm will start sounding. The alarm can be disarmed by holding a valid key to the metal contact (or alternatively by pressing the Sesame button). This gives a 2-second opening pulse to the relay, allowing the user to open the door. If the door has not been opened after 3* seconds, the KY-05 will give a 1-second closing pulse to the relay and return to the 'Guard' state.

KY-05 operation
state diagram

After the door has been open for 60 seconds, the KY-05 will start sounding short reminder beeps every 10 seconds. If a valid key is held to the metal contact, the reminder beeps will stop for a further 60 seconds. When the user closes the door, the KY-05 will give a 1-second closing pulse to the relay and return to the 'Guard' state.

The KY-05 will start with a short beep after powerup. If a non-validated Dallas key is held to the metal contact while the KY-05 is in the 'Guard' state, the alarm will sound for 1.5 seconds.

The state of the KY-05 electronic lock will be reflected in the flashing of the red LED, as follows:

The 'Guard' state has a slow blink with a 2-second period (1 second on, 1 second off).
When the alarm is sounding the LED will flash faster (1-second period).
The LED will also show this 1-second flash while opening or closing the relay or waiting for the user to open the door.
The LED will simply be on all the time when the door has been opened properly.
The LED will flash quickly (1-second/half-second period) during the adding/deleting of keys (see next section).
If the LED should ever blink very slowly, with a 4-second period, there is a problem with the internal non-volatile memory. The KY-05 unit has to be repaired.

* If the Sesame button was pressed the KY-05 will wait 15 seconds instead of 3 seconds.

Key management

The KY-05 has a non-volatile memory containing the serial numbers of electronic keys. Only the keys that have their serial number listed in this memory are recognised as valid keys by the KY-05. The standard memory has the capacity to store up to 31 keys. There is always one 'Master key'; only the owner of this Master key is able to add new keys to the memory or remove them from it. The non-volatile memory can be cleared of all keys (including the Master key) by keeping the 'Reset input' of the KY-05 short-circuited during the full first second after power-up. The LED will start to flash quickly (half-second flash) to indicate that it's waiting for the first new electronic key. This first key to be held to the metal contact will be the new Master key. Once set, the Master key can only be changed by performing this 'Remove all keys' procedure again.

The owner of the Master key can add or remove user keys any time using the following procedure:

  1. Open the door properly, just like usual (LED is now on)
  2. Hold the Master key to the metal contact (LED is now flashing with a 1-second period)
  3. Hold the user key to the metal contact within the next 2 seconds (LED is flashing quicker, with a half-second period)
  4. Hold the Master key to the metal contact again within the next 2 seconds (A short beep will sound; the LED will stop flashing again)
  5. Repeat step 2-4 with other keys as often as needed
  6. Close the door.

This procedure will add the user if it was not yet listed in the memory; if it was listed this procedure will remove it.

When a key is added to the memory, the beep will be slightly higher in pitch than usual. When it is removed, the beep will be slightly lower in pitch than usual. On attempting to add a key to a full memory, the KY-05 will give three short low-pitched beeps.

If the 'Master key/user key/Master key' sequence is not performed quickly enough, the KY-05 will return to the 'Door opened' state and the LED will stop flashing. The procedure can then be attempted again.

The KY-05 technical specifications.
The main KY-series page.

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