two work fine on my current robot. I am to up the ante by using my arduino on a larger system which may require as much as 8 on my offroading one. I will also have 2 temperature sensors to monitor my mootor driver temp and switch the fan on when needed.
I am thinking of putting a 5v regulator with a common ground to power up my sensors. any thoughts? i have a 5v 1amp regulator gathering dust.
The only current specification I can find for the HC-SR04 is "quiescent current : <2mA".
I'm guessing that the active current draw is low enough that running 8 of them off the Arduino power rail would not be a problem.
2ma is great. i will let you know how i go.