#### What Will I Learn?

- About Low-pass Signal Filter.
- How to construct the low-pass Signal filter
- How to  the low-pass Signal filter
#### Requirements
- Basic in Constructing Electronics circuit.
- Electronics Components.
- Electronics Laboratory Equipments.



#### Difficulty
- Intermediate
#### Tutorial Contents


   In Electronics communication  where it involves lots of signals’ applications, filter plays a very important role in it. 

The experiment that we had done which is a Sallen key low-pass filter is one of it. 
Applications would be that if you had a large interfering signal you needed to get rid-off this designed can be use. To get lots of attenuation, you could cascade several RC filters depending on your design.

#### What is  a Filter?
   Filter is a device or process that removes some unwanted components or features from a signal. Filtering is a class of signal processing, the defining feature of filters being the complete or partial suppression of some aspect of the signal. Most often, this means removing some frequencies or frequency bands. 

However, filters do not exclusively act in the frequency domain; especially in the field of image processing many other targets for filtering exist. Correlations can be removed for certain frequency components and not for others without having to act in the frequency domain. Filters are widely used in electronics and telecommunication, in radio, television, audio recording, radar, control systems, music synthesis, image processing and many others.
#### The Circuit Diagram
![image.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519464072/sr5r6aez2fgxpg0ft2rv.png)
#### Electronics Components
Resistors - 33k  and 10k 2 pcs.each.
Capacitors - 0.22uf 2 pcs. IC - LM-741 operational amplifier.

#### Procedure:
1. Construct the circuit based in the diagram above and supply it with power source
2. Input a certain signal from any signal generator to the circuit and generator signal must have an adjustable frequency.
3. Measure the  input and out signal through oscilloscope use channel 1 and  2 to visualize the effect of filtering.
4. Calculate the cutt-off frequency to figure out where the frequency started to be filtered by the formula below.!https://res.cloudinary.com/hpiynhbhq/image/upload/v1519465048/zpqtdh9gn5gqxzxmuyso.png
5. Observe the filtering action above the cutt-off frequency since we are using  lowpass filter.

#### Signal Filtering Action:

![image.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519465411/zgy6vxhmtg9jrlherfjo.png)
In this illustration we were inputting about 5 hz signal so it doesn't yet start its filtering action but when it reaches above the calculated cutt-off frequency we will notice a lot of attenuation in that circuit the calculate cutt-off frequency would be 20hz so above that signal will be attenuated.

![image.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519465801/oowqzfx9ygir1rvqartf.png)

  This is at 10 hz signal notice that signal still passes because we haven't yet reached to 20 hz above.
![image.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519466075/gehjn1qgs2wuplcpufnt.png)
![image.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519466199/vjjxxcq5s9wy16qqvgsg.png)

At 60 Hz we notice a noticeable attenuation of its amplitude.
![image.png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519466375/lxk1nqjvjgdc7sepfraa.png)

At 75 hz Signal is already being filtered we observed that its amplitude almost go straight means it is already a small amount of its amplitude.

#### How to  Apply the Signal Filtering circuit in Audio system.

 in Audio system in Audio system in Audio system.

 An RL and RC circuits act as a passive high-pass and low-pass audio frequency filters. Their effect is clearly evident when listening to music (or white noise).
 The way how we do the actual connections to filter the noise in the audio systems are just easy.Connect the Resistor and capacitor based in the circuit below and choose the frequency you want to eliminate in the desired audio tone output.
![lopass (1).png](https://res.cloudinary.com/hpiynhbhq/image/upload/v1519467854/rv8cf8hkfgaiah2xkhfq.png)


If you are experimenting with low output signal audio system you can amplify it by operational amplifiers just like at the first diagram above to have a greater output power but the op-amp must be a high power rating also don't use any more the LM-741 for greater power application.
You can also replace the resistor with potentiometer for you to adjust the cutt-off frequency that you desired so the effects would be a change of tone of the speaker.

And there you have it you can already connect that circuit to your audio output if you want to have some fun with the output tone of your speaker or audio amplifier just remember the power rating of your components when your using IC like op-amps.
This would be great for engineering students and also for electronics hobbyist. 


Hope you guys upvote my first post in this platform and I hope this will be approve also. 
#### Curriculum
This is still my first contribution at the moment.

<br /><hr/><em>Posted on <a href="https://utopian.io/utopian-io/@ceszar/electronics-tutorial-signal-filter-designed-sallen-key">Utopian.io -  Rewarding Open Source Contributors</a></em><hr/>