Hi, I have a question about some interference I have been getting on the PCB board I just etched. I designed a circuit to convert an audio signal into a visual light show using the MSGEQ7 chip and a strand of g-35 color effect lights but it seems that the bass bands are picking up some other signal on the board. When I had the circuit everything worked perfectly but now the lights controlled by the lower ranges of the audio signal flicker near constantly. Is this due to the fact that I am using the analog channels of the Arduino as digital outputs near to the analog channel that is sampling the MSGEQ7? Any help would be greatly appreciated. I have attached a picture of the board and the schematic I am using.
Bump.
How are you separating the frequency bands?? What is the output impedance of those outputs?
If they are fairly low impedance (say 1000 ohms) , there should not be much crosstalk.
Disconnect the signal to the Bass channel, put a 1000 ohm resistor to ground, and see if you still have crosstalk that you can attribute to your PCB.. If not, check shielding, grounding, output impedance etc...
Let us know what you see / hear...
Check the values of your Rs & Cs around the MSGEQ7.
Your values seem kind of a lot different compared to the typical application values on sheet 4.
And you left its Reset pin floating, that's generally not good.
I also don't see any 0.1uF caps on the '328 VCC/AVCC pins.
And you're driving an LED directly from D5 - that will end up damaging the output pin or the LED before too long.
Hmm - doesn't look to me that your schematic matches the board - go back and add some signal names so all the connections made on the board show up on the schematic. Such as pins 3 & 4 from the MSGEQ7.
I've used the msgeq7 before nd the only crosstalk/feedback I would ever get is at the. Higher end channel due to the pwm frequency, but that would only appear if I touched the raw led strip, I guess acting as a sort of antenna, enough anyway to reintroduce the pwm signal to trick the msgeq7
the only time I've had low channels picking up noise is from. The 60hz mains frequency noise which hppened in once during testing it was placed across an extension cord
How about the code you re using? I imagine the outputs aren't toggling at the exact frequency of your interference, then I would say maybe but most likely its fom something else as the digital outputs change so fast it wouldn't pick it up, and also decoupling is necessary, small fluctuation in avcc my cause noise that your unkown code may read
I found on certain channels I had to ignore noise below a certain reading, variying on location
for the low channel it had to be above 35 to 100% get rid of 60hz noise, in my car I had to raise the higher channels to 40 to rid of noise from the cars electronics
Sorry it's taken so long for me to get back to you and thanks for helping. I figured out that the interference is not in the msgeq7 but rather the power supply. I uploaded code to the Arduino to filter values below 100 out and it didn't help. I then ran the pcb of the 5v power of my official Arduino board and it took care of the problem. What is weird is that I am using a 5v off brand ipod charger so one would think that the output would be pretty smooth. Should I just add a few small caps across 5v and GND?
Caps will help some, perhaps a properly sized inductor would help, and maybe even some shielding of the power supply in case its has alot of emi