I am building a home beer brewing rig that has several electrically actuated components controlled by an Arduino.
The typical scheme is Arduino -> Shift Register -> Relay -> Component.
One of the components is an electrical BBQ igniter. The problem is that when I turn it on, the shift registers go all wonky and randomly turn their outputs on and off with every spark.
I realize that the main problem is that the igniter is being energized by the same power supply as the rest of the system and that it creates a power surge when it generates a spark. But, how do I neutralize that problem?
One idea I had was to put a capacitor across the igniter input. That didn't help. My analog circuit knowledge is not so awesome.
Anybody have any ideas? Much appreciated.
P.S. The shift registers are 74HC595.
Best Answer
The capacitors should go across the power supply terminals of the various components like the shift register and igniter, to bypass noise riding on top of the power. When noise comes from some other device, the capacitor can help shunt it to ground. Reciprocally, when a sudden, brief current demand comes from the local device near that capacitor, the capacitor supplies the demand, so that there is less of an effect on distant parts of the circuit.
For better answers, you might want to show the exact circuit diagram, including power supply details.