hi frens,i'm new here...i would like to build the following project.this circuit is designed to activate the relay for certain period time only. can anyone help me how to make the relay activated continuosly after correct pin code enter.
Description
Substitutions C1 1 1uF 25V Electrolytic Capacitor C2 1 220uF 25V Electrolytic Capacitor R1 1 2.2K 1/4W Resistor Q1 1 2N3904 NPN Transistor 2N2222 D1 1 1N4148 Rectifier Diode 1N4001-1N4007 K1 1 12V SPDT Relay Any appropriate relay with 12V coil U1 1 LS7220 Digital Lock IC S1-S12 12 SPST Momentary Pushbutton Keypad (see notes) HD1 1 12 Position Header
It looks like you are referring to the digital keypad lock.
Check the datasheet for the LS7220. It may have a mode that allows this and the only requirement would be bringing a pin high or low.
Failing that, the simplest possible way of achieving this is to use a DPST relay. Connect one of the sets of contacts across the transistor. This will essentially turn the relay into a latching relay and it won't drop out until power is reset.
need experts advice
Posted - Sep 01 2009 : 3:06:59 PM
