I’m designing a Raspberry Pi hat for a class that I am teaching, and am worried about power consumption. I’d built an earlier version of the hat without any problems AFAICT, but realize now that I need to take this into account. I’d called digit-key tech support, and they suggested I post this here to get a definitive answer. In case it’s not already evident, my expertise is not in EE, so I’d like someone to double-check or correct my reasoning/calculations.
First, I understand that each Raspberry Pi 3B pin should draw <16 mA, and in total < 100 mA.
My circuit has 4 LEDs with 220 ohm resistors, 2 switches, a DHT22 and a buzzer. The DHT22 draws 1.5 mA max, so it’s fine. I have a CEM1203 buzzer which draws a max current of 35 mA. Now I’d used this in an earlier class and AFAICT it didn’t do any damage … was I just lucky? I’m using the wiringPi library to drive it.
The switches have a large pulldown resistor, so I don’t think they’ll be a factor.
Finally, with the LEDs, if I have GPIO Pin >> 220 ohm Resistor >> LED >> Ground, I figure that with a total voltage drop of 3.3V, I = 3.3/220 = 15 mA mean that I’ll be OK (I might go for 330 just to make it 10 mA).
Thanks for any advice/suggestions.