Starting on getting sound amplification working. I’ve previously failed several times for various reasons like stupidity and randomly plugging wires into places they don’t belong. This time I have a few sacrifical speakers and a new amplifier board to try. I’ve gone with a “PAM8302” which cost just a couple of bucks and claims 1.5W @ 8 ohms. Previously I’d tried a 60W amp not realising that this was probably complete overkill.

So it was suggested to me that the first thing to try was just a CD player or computer. Well, I realised I still had an old “Doctor Who” NBTV format file on the CD that I used to use for NBTV signal source, so I hooked that up again, and tried to film with one hand while holding the positive/negative leads onto the output from the CD player. I was also powering the amplifier itself from the Arduino, and running the Nipkow disc and Nextion LCD display at the same time, so I had a fair test of power usage with everything configured. All that’s different in this test is that the sound is NOT coming from the PWM pin on the Arduino, but instead direct from the headphone out (not line out) on the CD player. I cranked up the volume on the CD player to MAX.

I wanted to see if the speaker was “loud enough” compared to the racket from the motor as it’s stuttering and doing it’s thing to keep the disk in synch. Well, it is. Just. But I expect the motor to be a lot quieter when I bury it out the back and in an enclosure. I also will be trying a few different motors and perhaps a higher speed too, just to try and optimise that side of things.

So, the upshot of all this – I confirm that the tiny 1.5W amp is sufficient for my needs, that it works, that the “power budget” on the Arduino seems to be sufficient.

So now I can move on to the somewhat tricky problem of using the PWM output from the Arduino to drive the speaker. I’m going to be using a RC filter to convert the PWM to analog, and hopefully all will work as heard here.

This is a part of my video log of my mechanical TV build. To follow progress and for all the instructions on how to build your own, visit the NBTV forum at https://www.taswegian.com/NBTV/forum/viewforum.php?f=28

, https://i.ytimg.com/vi/u3Ij-u5Ykq4/hqdefault.jpg

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