Electronic Lock using Switches

Many electronic code lock are available in market some using microcontroller and many more using discrete electronics components. But because of large components it uses, they are bulky and cannot be handy to use.

So we have described a circuit which uses commonly available switches and a alarm to protect your almirah and other important documents from theft. In this circuit lock will only be open when correct sequence of switches is pressed, otherwise it will on the alarm to alert you that somebody has tried to enter into a restricted area.

Main advantage of this circuit is it is very simple, easy to assemble and small in size so that you can easily carry. You can also increase the number of switches to increase the complicity of the circuit. And in ideal case it does not draw any current, giving you long battery life.

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Fig. 1: Prortoytpe of Electronic Lock using Switches Circuit on Breadboard

Assemble the circuit properly. The switch we are using is push to make switch means when you press the switch it conducts and when you release the button switch become disconnected. In our circuit correct code is S1, S3, S5, S8 by pressing this

Fig. 2: Protoytpe of Electronic Lock using Switches Circuit on Breadboard

code lock will become open and if any other switch is press in between than we will get an alarm.

As you can see from circuit diagram when you press the switch S1 whose one end is connected with power supply and another end is connected with switch S3 so when you press the switch S1 power supply from switch S1 is provided to switch S3 and then to switch S5 and then to S8 if correct code is pressed. Now through switch S8 we have connected a relay whose one end is ground and another end is getting supply so relay get energies and you can connect your lock through solenoid so that when correct sequence is pressed door will become open for some time.

Now any other switch like S2, S4, S6,S7 is pressed whose one is connected with power supply and buzzer and another is connected to ground so whenever you press any of this switch buzzer will get power supply and start sounding indicates you that wrong code has been pressed. You can change the code according to you.

Before mounting the switches verify that all are working fine or not. This can be done with the help of multimeter. Just set you multimeter in the continuity test mode and put both the leads of multimeter on both the leads of switch (do not worry about polarity) initially no sound will come. Now press the switch, sound should come if this phenomenon is occurring than your switch is good otherwise it is faulty. You can also use on/off switch in place of push to on switch.