Joao Wilbert
How to Make (almost) Anything 2019

Week 9: Output Devices

For this week I decided to build an output amplifier and program the ATTINY using the audio example. For it I redesigned Neil's speaker output board in Eagle. My initial idea was to build an amplifier for my vinyl cut speaker, but I decided to focus on the microphpne aspect of my project and do this assignment just to learn how to design the board and get a simple sound output.

schematic of the board.

This week was a little tough as my son, myself and my wife got really will so I didn't have too much time to work on the assingment, so I decided to do something simply and stick to the basics in designing a new board for an output device and test it with the hello world code.

My first step was to work backwards from Neil's example and design my own circuit based on the same principle of using the transistor to modulate and push the coil of the speaker. Here is the scheamatic I designed in Eagle.

Designing the board didn't take too much time, I layouted the board in Eagle using the N mosfet to drive the speaker. I designed the board without much issue as the circuit was really simple. One thing I made sure was to use the MOSFET with 1.1A and 30amps as we probably need to drive a lot of current into the speaker. Here is the final board design.

I then I milled the board with the 1/64 for traces and 1/32 for outline, I then and stuffed with the components without a problem - I always try to make a guide (red board) that I can refer to the components when making the board. I used the a separate power source 9V for the speaker that is then applied PWM.

I used the AVRDUDE programmer to upload the speaker hello world software on to the board.

I connected the speaker to the board and uploaded the code to ATTINY using AVR dude, when doing that I could start hearing the frequency sounds generated from the hello world code.

Here is the amount of current that it draws from the function generator to drive the 8ohm speaker. This is what the speaker is using when playing.