Tuesday, November 22, 2011

Kunci Kombinasi Tombol Digital

This simple circuit is the electronic version of the combination lock. Using the special purpose LS7220 digital lock IC, the circuit allows a 4 digit combination of your choice to activate a relay for a set period of time. This relay can then be used to trigger a lock solenoid, enable a starter button, open a motorized door, or many other tasks that require a momentary signal.


Total Qty.
C111uF 25V Electrolytic Capacitor
C21220uF 25V Electrolytic Capacitor
R112.2K 1/4W Resistor
Q112N3904 NPN Transistor2N2222
D111N4148 Rectifier Diode1N4001-1N4007
K1112V SPDT RelayAny appropriate relay with 12V coil
U11LS7220 Digital Lock IC
S1-S1212SPST Momentary PushbuttonKeypad (see notes)
HD1112 Position Header

  1. To set the combination, wire the appropriate switches to U1 pins 3, 4, 5 and 6 using the header. For example if S1 was connected to pin 3, S2 to pin 4, S3 to pin 5 and S4 to pin 6, the combination would be 1,2,3,4. Now wire all other unused switches across the header to pin 2 of U1. In this way you can create any 4 digit combination you want. Pin 2 is the reset pin, so connecting all unused keys to it assures that the entire combination must be reentered if an incorrect key is pressed.
  2. When the appropriate combination is entered, the relay is activated for a period of time determined by C1. The 1uF capacitor specified in the parts list will result in an on-time of roughly 5 seconds. Increase the value of C1 to increase this time.
  3. An easy way to make a keypad is to buy 12 PC board mount pushbuttons and then etch a PC board so that the buttons are in 4 rows of 3, similar to a telephone keypad. Place this in a case and then use a label maker or transfer letters to add your numbers to the tops of the pushbuttons. You can also use a pre made keypad but keep in mind that you need a pad which provides an output for each key. Most pads available have the keys connected to provide a row and column signal when they are pressed.
Source : www.aaroncake.net


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