I Had to build this for my sister who has hearing problem which lets her know when someone's knocking at the door downstairs. This device is easy to build and can be used anywhere in the house. It lights up with the slightest noise made either from knocking door or talking. Let's you know when someone is at the door when u are upstairs in your bedroom and someone's knocking.

Step 1: Components Needed

You just need few components, I've listed each clearly and added the pics of how it looks like incase you are a beginner.
1. 10K Resistor(1)
2. 100K resistor (3)
3. 330K resistor (1)
4. 47K Resistor (3)
5. 47 resistor (3)
6. 1.5M resistor (3)
7. 100nF capacitor (3)
8. 100uF capacitor(1)
9. BC547B transistor (3)
10. BC557 transistor (2)
11. 9V battery
12. LEDs
13. Microphone (M300)
14. RV1 (1) to adjust the sensitivity
15. Soldering iron(if u soldering it)
16. Battery holder

Step 2: Getting Started

Above is the circuit diagram of the whole circuit

Step 3: Getting On

You can either use a solderless breadboard to first check how it works or go straight to solder the component on a breadboard when you are sure u understand the circuit. I started on a solderless breadboard and decided to go straight to solder it on a breadboard. You can create your own breadboard in green. I'll make a video on how to do that in my next project

Step 4: Soldering the Components

Follow the circuit diagram and arrange the components as it appears on the breadboard and solder it nicely bit by bit

Step 5: Finalising

After all components are done on the breadboard, get something to hold the battery in place, it could be a plastic battery holder or anything you thing is able to firmly hold it in place.

Step 6:

<p>Please can you try to explain me the circuit diagram exactly and what each components does</p>
<p>hi, I have redrawn a much simpler circuit u can try on a breadboard and it works great. Just follow each connection as shown accurately . </p><p>For the function of each component, all the resistors act to reduce current and lower the voltage levels to each component for it to have exactly the right amount of current or voltage it needs to work with. </p><p>The transistors are amplifiers, it amplifiers the noise received and can also act as switching between the signals by its operation.</p><p>LEDs light</p><p>Battery gives power</p><p>Capacitors acts as filter, and also blocks dc voltage.</p><p>Hope that's helps..</p>
<p>I still dont understand how each part functions as it does, if its not to much trouble, please explain it to me as well as the numerical aspect of the circuit</p><p>thanks in advance</p>
<p>can we make that circuit without trimmer(RV1)?</p>
<p>A trimmer of value 220K means we can vary the resistance from 0 to 220K, hence any potentiometer within same range will work. If u take the trimmer out, that means u won't be able to vary the sensitivity of the circuit. But it should work without it. Give it a trial and observe how sensitive it is to sound. Let me know how u get along and I will gladly help. Cheers!</p>

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