Please read the how to get the most from the forum post. The post contains information on what we need to know in order to help you.
Lack of information makes answering difficult.
What Arduino board? How is it powered? What is connected to the PCF8574 chips?
Where is your code?
Where is your schematic?
Please read the forum guidelines to see how to properly post code and some information on making a good post.
Use the IDE autoformat tool (ctrl-t or Tools, Auto format) before posting code in code tags.