I have wired up an ESP8266 wifi uC to a MAX7219 7-segment driver. The setup works well, except that the circuit seems susceptible to external noise. The main issue I have noticed is that activating a light fixture on the same circuit will mess with the device (the display gets scrambled, or even goes blank).
The circuit is currently setup on a bread board with wires everywhere, as shown in photos below. So I thought the issue was just that all these loose wires were acting as antennas (and maybe that is the answer). But the problem seems much reduced if I plug my device into another outlet ("B" on my sketch), which makes me think it is actually a power supply spike and that my circuit is not adequately filtered.
I am powering the whole thing off an old ATX power supply, which I thought would be pretty resilient to mains noise.
I have 10uF and 0.1uF capacitors on the circuit, as recommended on the Arduino site. I think I have the caps fairly close to the leads, especially for the MAX7219. I have tried several combinations of capacitors, but the behaviour seems to be the same.
I am just wondering if I am on the right track with power line issues? Or if I am wasting my time and this circuit will never work properly until I get rid of the "antenna" wires and use a proper circuit board?