Powering PCB with USB and Adepter

Hi everyone, I have working systems and I want to make a PCB for it. My system needs 24V (for stepper and relay) and 9V for RFID and 5V (for ADC reads) and 3.3 V for ethernet. I am using 2 switch regulator 24->12 , 12->5 and I am using 2 linear voltage regulator 12->9 and 5-> 3.3V. I have two question about it.

1-) My system needs USB for code upload. So I need to use USB cable at least one time. Then, I will use these regulators for powering. I have schematic here :

What I want to ask is; when I try to upload code to microcontroller, I won't plugged 24V adepter. I will upload code through to USB cable so will V_USB cause something ? When I use micro USB, V_USB will equal 5V. So 5V output power will cause something for R-78E5-0.5 (top of the right)?

I am asking because I made small experiment . I used ld1337. I connected 3.3V to OUTPUT and GND to GND. I measured 2.64V on INPUT.

2-) My second question is, RFID recommends 7809 but people says it is too old you should try something newer. Is there any suggestions for Low dropout regulator for 9V? or should I stick with what RFID's data sheet recommends (7809).
Thank you.

That’s a lot of power supply lines - I’d want to look at simplifying ..

7809 is good single chip regulator , if the load is light and it doesn’t therefore generate a lot of heat , then it’s fine .

Yes, 12V to 9V with maximum 120mA. 360 mW. I can't simplify because I need to use 24V for my stepper and I want to power circuit only with one adepter. So I need to use like this I guess. (Do you want me to take their close screenshoot by one by I can ).

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.