3 CHANNEL AUDIO MIXER Integrated With an FM Radio Transmitter

Hey everyone, in this article I will be guilding you to build your own 3 CHANNEL AUDIO MIXER integrated with an FM radio transmitter

Step 1: Introduction

Have you ever wanted to connect your voice signal to an amplifier system,or even have your friends speak simultaneously on the same amplifier. Having the challenge of designing a system like that is common,and in this article, we will show you step to step of how to make a 3 CHANNEL AUDIO MIXER integrated with an FM radio transmitter. Which you can not only speak with your friends, but you will have more people listening to you on the frequency that you preset, where in my system was 87.9fm.


You can watch the step to step video via the link

https://www.youtube.com/watch?v=GaZTiAn8Rb0

Step 2: Block Diagram

In this design, the building block of the system is evidently presented using a simple block diagram, as presented

[ [ Video(https://youtu.be/GaZTiAn8Rb0) ] ]

Step 3: Voice Inputs Settings and Circuit

making the voice input, consideration needs to be made, and for my design, I choose to use a condenser microphone.
This types of microphones acts like a capacitor unlike the other microphone that vibrate relative to the sound intensity coming through any source, I.e human voice.
If you connect the condenser mic to the system using it probe ( +ve and -ve ), you will not get the signal output, you will need to trigger it to generate or convert the voice signal to an electric signal, and that is what exactly the circuit above does.
The switch in all the voltage source of each mic is for control, and that is why I use the red switches for the 3 voice input,and the green LED for indication.

Step 4: Pre-amplifier CIRCUIT

The pre-amplifier setup from the above image, takes the signal from the 3 condenser microphone, and then feed it to a transistor base signal amplifier.
You can choose to couple the microphone signal to the pre-amplifier, if you would want to make a transmitter without coupling the mixer system. This choice is useful, as it will go a long way to make a design simple and easy to troubleshoot. But if you would want to continue the development as we did,you then don’t couple the pre-amplifier stage, as we are going to amplify them using the operational amplifier, which we will further take the signal output to the mixer system.

Step 5: OPERATIONAL AMPLIFIER

The mixer system comprises of the op-amp IC with few other components couple to it.

The image above, shows a typical configuration for an op-amp.
In this set up, I set the audio gain to 200 unit using a 10uf electrolytic capacitor at C4. this simply means that the IC multiplies the the input signal by 200 unit. Let say I have the signal coming from the microphone or aux cable to be 2 decibels, if the signal is sent to the op amp, it will be amplified by a factor of 200, which is 400 decibels. Isn't that massive?
I coupled C4 with a variable resistor in order to adjust the audio gain at every point in time.

Step 6: MIXER CIRCUIT

The image below shows the complete mixer circuitry.



From the image above, much modification wasn’t made, just few variable resistor were added and few switch.
3 op-amp chip were used as we have in the image below.

Step 7: PHYSICAL BOARD

After the OP-AMP channel have been developed, you will have the System look like this.

Much of explanations wont be made here, as we have the circuit diagram to express the connection.
The set up we have at the mixer circuitry houses different audio input and the adjustment for proper mixing.
Since the mixing is set by each user, according to the sound quality, one then need to follow the circuit correctly.

Step 8: CLASS a AUDIO AMPLIFIER

CLASS A AUDIO AMPLIFIER

The class A audio amplifier was used as an auxiliary amplifier for music, in case one don’t want to broadcast.
Using a linear adjustable switch, I can always flip to any amplifier ( op-amp and class A amplifier ) input and output .

Step 9: FM Transmitter

I assembled an FM radio transmitter module, and the circuit is presented.

Step 10: PHYSICAL BOARD

The physical board at this stage will be like this.

Step 11: HOOK UP THE WHOLE CIRCUIT

At this point, you will connect all the circutory together as the end parts of each circutory were indicated.

To get the PDF document of the connection coupling, check out the link below.

https://m.facebook.com/story.php?story_fbid=161398148748024&id=102574637963709

Step 12: PACKAGING

I used a 6/9 patrex box for the packaging,were I drilled the necessary hole for installation.u

Step 13: SPRAY CASING

I used a black and gray color for the spray job.

Step 14: ASSEMBLE COMPONENTS FOR INSTALLATION

All the components are assembled for installations.

Step 15: INSTALLATION

I installed the components with every other utility features of the system.

Step 16: COMPLETED SET UP

Now the System is ready for test!!!

Step 17: TEST

The System was tested,and the results were massive.

Step 18: FULFILLED PROJECT

At this point, you can now invite friends for a broadcast...

We made a broadcast and a live video which we uploaded on Facebook,we had people called in to our broadcast and that was amazing. To watch the video click the link below,

https://m.facebook.com/story.php?story_fbid=1168764636799018&id=438304376511718

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