Usually the project is a variation on the POV toy, which you see around online all of the time as a beginner electronics project. However, we decided to deviate from our traditional path this year and create our own synthesizer kit, with an SPI DAC, Audio Amplifier, Microcontroller and some buttons. There is also a possibility for programming in new wave forms via an optical link with a computer.
Click here to download the full size of the above Circuit.
To give a good overview of the whole project I plan on doing a write up on each part of the project as I go along. First up lets check the constraints of our Audio Amplifier and see if we can get it working in an appropriate way. The amplifier we are using is a TDA2822M and is a dual audio amplifier. We are not driving a stereo channel, so we will be using the TDA2822M in a bridge configuration inorder to both push and pull on the speaker dramatically increasing the amount of power we can drive through the speaker. The datasheet for the TDA2822M is where the schematic above was pulled from. The schematic is a basic bridge, which drives both sides of the speaker in mono for added power. It is important to note the gain of the circuit for future calculations since the output of or DAC will be full swing from 0V to 5V (or close). Thus we will need to divide those voltages so that we don`t clip everything to a funky looking square wave. At 1kHz the noted voltage gain is 39db, which is about Vin*89. 125. A rather respectable gain, which we will later have to contend with. I decided used to prototyping with breadboards, but this time I have decided to use protoboard and solder and skip breadboards completely. While breadboards are nice I find that if I spend the time to sit down fully plan what I am doing and soldering it down on to protoboard that I reach an end result faster. Once the soldering was done (see schematic above),...
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