We have a arduino mega and 6 pca9685 to connect 37 9g servo, 37 rgb led and 37 button, what kind of power supply we can use?
To work out what kind of power supply you need depends on a few different things. First of all you must ensure that you’re using the correct voltage for the Mega (5V). Second of all you need to have a supply which has a current rating greater than the total current draw of your circuit. So let’s go through what’s in your project:
Push buttons aren’t active components and don’t require any power to function so we can ignore those.
The power draw of the PCA9685 chips for the digital logic is fairly low so we can ignore that too.
The current draw that the mega2560 uses by itself is also quite low so we’ll ignore that as well.
So the main thing that will affect your current draw is the LEDs and the servo motor. You’ll need to look up the max current draw of your particular motor and add that to our LED calculations. So each RGB LED has 3 seperate LEDs inside which will draw approx. 20mA each at full brightness so the LED current draw is 3730.02 = 2.22 Amps. That is the rating if all of them were on at full white. That probably won’t happen often, but you want to allow for every situation. Now as responsible makers, we want to over-engineer our designs so if we take that 2.22 Amps, round up to 2.5 Amps to allow for the Mega, PCA9685, plus any stray current, all you’ll need to do is add the current draw of your servo and you will know what kind of current draw you need. If you use a 3 Amp supply you’ll be safeguarding yourself against any issues and give yourself some nice elbow room.