ELECTRONIC ACCESS CONTROL
Electronic Keypad Lock Control
Powered directly from 120Vac, no batteries. When at rest it uses virtually no power.
It is connected to a keyboard (not supplied) with any number of keys or push-buttons.
All the keys share a common wire which goes to #1. Four of the keys form the correct
password and are connected respectively to #2, #3, #4 and #5. The password is programmed
by the way the keys are connected and therefore will not be lost with a loss of power.
To change the password just use a small screwdriver to change the order in which the
keys are connected. All the other keys, with no limit as to number, are connected to #6
through #9 (they are in parallel so it does not matter which). Pressing any of these
"false" keys resets the system. It follows that the four keys which form the correct
password must be pressed in the correct order and no other keys can be pressed or the
system will be reset.
When the four correct keys are pressed successively in the correct order the relay will
be activated. The output contacts of the relay are available to connect or disconnect
any device which uses no more than 1 amp. The relay contacts have a normally open and
a normally closed outputs and either or both can be used.
The relay will remain activated until one of the "false" keys is pressed. Not only the
keys on the keypad can be used but also any other switches which can be placed elsewhere.
For example, if the relay will activate a motor which opens a door, then a switch can
be placed at the end of the opening of the door so the relay will rest when the door has
fully opened. Or if the relay only controls the lock then the extra switch can close
once the door has begun to open and this stops the activation of the lock.
The wire bridge on the board can be cut in which case the relay will automatically reset
itself after a few seconds
A practical example is to control a door or gate which has an electric lock, for example
as complement to an intercom lock or a garage door. In this case the wire bridge can be
cut so that the relay will reset itself after a few seconds. In doors moved by motors,
which require a longer and generally variable activation time, the reset can be done by
a switch at the end of travel, as explained above.
For other applications the reset can be done manually, either from the main keypad or
from switches installed elsewhere. This would be the case of systems which should remain
in a certain state indefinitely and should only be activated or deactivated by authorized
persons (motors, electric and electronic equipment, alarm systems, etc.)
Click on the photo to enlarge it.
#1 is the common wire from the keypad
Using a couple of screws through the two holes provided secure the unit to the wall or other
fixed object. Make the necessary connections following the diagram:
#2 is the first key of the password
#3 is the second key of the password
#4 is the third key of the password
#5 is the fourth key of the password
#6 through #9 are for all the "false" and reset keys.
There is no limit to the number which can be connected in parallel.
#10 is the output of the relay which is normally open (NO)
#11 is the common contact of the output contacts
#12 is the output of the relay which is normally closed (NC)
Finally we will connect the power supply, 120 Vac, between #13 and #14
(Or 220 Vac between #13 and #15)
If we want the relay to reset itself after a few seconds then we will cut the wire bridge
which is in the opposite en of the connector and is marked with a marker.
Once the electrical connections have been completed put the cover in place and
secure it with the four screws which go in the sides.
135 x 85 x 45 mm (5.3" x 3.3" x 1.8")
The metal box is designed to receive the wires directly from the wall. If the case that the wires
do not come from inside the wall the metal cover can be cut to accommodate them or a block of wood
or other material can be used as a standoff so there will be enough space for the cables between
The price only includes the electronic circuit with its mounting box and does not include the
keypad or the electro-mechanical lock (what is mounted on the door itself) which must be purchased
Price: USA: $30 plus $10 S&H. , Europe: 25 EUR + 15 EUR S+H
For those who would want to build it themselves here is the schematic diagram: