Project Help

https://www.safe.co.uk/products/ring-smart-video-doorbell-2.html?ACODE=googlebase&gclid=Cj0KCQiAtJbTBRDkARIsAIA0a5PkltIwgPV1ixG1CF5SFSF3lmVbiJQ_UZLRsY1kUNOXaJtE7uVmTjMaArn7EALw_wcB

(usual disclaimer)

A pressure mat would be the simplest method if you have a door mat or carpet to put it under. It consists of two conductive foils separated by a perforated low density foam which allows contact between the foils to be made when pressure is applied by someone standing on the mat. You can then use your micro controller to do what ever you wish it to do. A complete setup with controller and alarm is about $25.

If you want to be more adventurous, then a piezo sensor could be used to detect actual footsteps or even door knocking etc, but that could become a bit annoying unless it was very restricted in its sensor range. A pretty simple timer circuit and frequency generator would give you the desired alarm parameters.

Below is a fairly easy one that I picked up off the net

The circuit uses a thin piezoelectric plate, senses the vibration generated on knocking a surface (such as a door or a table) to activate the alarm and can also be used to safeguard motor vehicles. The piezoelectric plate is used as the sensor. It consist IC 555 Timer to which speaker is connected at the output. Piezoelectric material is used at the input in order to convert any mechanical vibration into electrical variation. When someone knocks on the door, the piezoelectric sensor generates an electrical signal, which is amplified by transistors T1, T2, T3. The amplified signal is rectified using the Diode and resistor connected in parallel to each other and then this rectified output is filtered to produce a low-level DC voltage, which is further amplified by the remaining transistors T5,T6 The final output from the collector of PNP transistor T6 is applied to reset pin 4 of 555 Timer that is wired as an astable multi vibrator. Whenever the collector of transistor T6 goes high, the astable multi vibrator activates to sound an alarm through the speaker. When the circuit receives an input signal due to knocking, the alarm gets activated for about 7 seconds. A led is placed at the output of the IC 555 Timer. The circuit operates off a 9V or a 12V battery.

I just had it pointed out to me that the circuit I posted for the alarm apparently does not appear on an android tablet. It shows OK on my laptop.

I was lazy and just copied and pasted which may have caused the problem.

Here it is again as a picture. Hope that works.

Thank you so much.It is really interesting. Please can you clearly show me thé way it is with the microcontroller ?

My supervisor wants It realized with the microcontroller.

Nah! I've done enough of your homework.

Time for you to have a go yourself.

Surely your supervisor has given you some insight into what you're supposed to be doing before setting this task.

Doing this with a Microcontroller is totally different, and in a lot of ways much easier.

The Microcontroller has inputs you connect the pressure mat (in this case) to and outputs which you can connect up to a (say) a relay or transistor to give enough power to drive a bell. The logic is then done inside the Microcontroller once you program it up.

Start with learning the basics on Microcontroller operation and programming, then you can implement the simple steps of detect pressure mat operation (closing of circuit) ---> activate alarm bell output to turn on alarm. I am assuming this course you are doing has already given you the necessary knowledge to attempt to program and use the Microcontroller (otherwise the supervisor wouldn't be pushing you all to use it).

You will need to write the software function and program the Microcontroller yourself (which is about 80 to 90% of the actual project work).

Enjoy.

Thank you for your explanation ! ! ! ! ! Thanks ! ! !

Pressure switch doormat, like this.

Ideal Security Inc. SK630 Pressure Mat Alarm with Chime