Hi I'm looking to power 48x 28BYJ-48 stepper motors with ULN2003s to build a clock. The steppers will rotate every minute.
My circuit consists of a DOIT ESP32 WROOM, a DS3231 RTC and 24x 74HC795 shift registers daisy chained together. For every shift register, there are two ULN2003s attached, each driving its own 28BYJ-48 stepper motor. Via SPI I pass out bytes as required to step the stepper motors. This works as expected running 5 stepper motors. (https://youtu.be/al-xNNQv7To). As soon as a stepper arrives at its destination there is no signal passed to the ULN2003, so it turns off and as far as I know, draws no power (i.e no holding power required). The ESP32 will not be connected to the internet, or doing anything else other than passing the signal via SPI and powering the RTC
I'm now after some guidance in powering the project in the safest way.
See below my calculations. Each coil needs 110mA, and have 2 coils on per motor at any given time = 220mA per stepper. Each stepper is 5V, hence we have 220mA * 5V = 1.1 W per stepper. We have 48 steppers, all of which could be on at the same time. Hence a total of 52.8W. So if I bump that up to 55W to be on the safe side to power the whole system (ESP32 etc.) And given the steppers are 5V, I need 11A power supply.
So I guess my question is, is this safe? and how would I go about doing it? I'm in Australia, so 240V AC.
I'm guessing I need something that will convert 240VAC into 5VDC at 11A. And then something else that will convert this to say 7v to run the ESP32 (using its internal voltage regulator)
Would a 5V 12A LED driver (like this https://www.aliexpress.com/item/33052797791.html) be suitable? Although, then how do I power the ESP32 (with a boost converter?)