This is basically custom ATMega644p based talking Alarm clock I'm working on. I made PCB via OSH Park, added Adafruit's wave shield and Sure's 32x16 bicolor LED matrix for display. I'm now trying to amplify audio form WaveShield, so built a breadboard TDA2822 based amp (schematic straight from datasheet). It's getting a lot of (digital?) noise, especially when I'm scrolling text on the screen as you can see in this video:
Ignore Temperature, I don't have sensor connected yet
This is kind of a show stopper for me, since it's supposed to be alarm clock, and I don't want it humming and making weird noises all night near sleeping person's ear. Since I'm somewhat new to electronics, can someone make a suggestion what I can do to eliminate idle humming and reduce digital noise? Perhaps I need some kind of gate or filter? I have no idea... Maybe there are inexpensive ICs that can do that?
Another idea I had is to turn off amp when no audio is being sent (via transistor connected to digital pin on ATMega chip perhaps?).
Gotta clean up the wiring to start. Its a little antenna farm now, lots of radiating sources.
Also, try putting some caps across pins 5/6 on WS2, see if that quiets the power supply noise some.
I mean start making it into a neat assembly. The prototype works, yes? Now neaten up the wiring so there is not such a jumble of wires.
When current flows and signals change state, they emit energy, which is being picked up & amplified by wave shield.
CrossRoads:
I mean start making it into a neat assembly. The prototype works, yes? Now neaten up the wiring so there is not such a jumble of wires.
When current flows and signals change state, they emit energy, which is being picked up & amplified by wave shield.
Thanks! I made some progress btw. Looks like main issue was breadboard wiring. I rebuilt amp using LM386 chip and soldered everything to a perfboard. Now noise is almost gone, it sounds very acceptable.
But I still want a way to turn off/on power to the amp on demand from ATMega chip. Anyone done something like this? I presume NPN transistor should accomplish task, but I never worked with transistors...
It is hard to say about switching power as your schematic doesn’t show any amplifier.
If anything, a PNP transistor or P-channel MOSFET could be used as a switch in the power line to a LM386.
CrossRoads:
It is hard to say about switching power as your schematic doesn’t show any amplifier.
If anything, a PNP transistor or P-channel MOSFET could be used as a switch in the power line to a LM386.
I didn’t have it there at a time,just added. Will it work like described with NPN transistor?
