Hi all.
I am doing ESP32 control stepper motor, wiring as picture below, used a desktop power supply (A) to supply 3.3v to A4988 VDD, and a ADAPTER POWER (B) to supply 12V for motor, what said strange is the measurements done when A power ON and B power OFF. where the 110vAC from?
thanks.

 

Is the logic power supply ground connected to the other grounds?

 

Is the logic power supply ground connected to the other grounds?

the ESP32 used USB cable from a laptop during testing. but the measurement done independently, I mean not connected to any others, just A and B.

 

the ESP32 used USB cable from a laptop during testing. but the measurement done independently, I mean not connected to any others, just A and B.

Was there a common ground between the ESP32 and the rest of the system?

 

Was there a common ground between the ESP32 and the rest of the system?

The reason for the incident is precisely because the testing failed when connected a common ground from A's GND to ESP32's GND, so the measurement and post happened. the measurement made only with A and B, all connections cut when measued.

 

It would help if you provided a complete schematic of how you actually have things set up. Your present diagram makes no sense regarding the "logic power supply" box. What is powering it? What is it powering? What, if anything, are the black and red wires leaving it and going to the right connected to?

Are the grounds on the two power supplies you show floating? If not, what are they referenced to?

What are the voltages in your table measured relative to?

What are points of each measurement in your table? You have 3.3V- listed. Which wire in your diagram is that? Same for the others.

 

It would help if you provided a complete schematic of how you actually have things set up. Your present diagram makes no sense regarding the "logic power supply" box. What is powering it? What is it powering? What, if anything, are the black and red wires leaving it and going to the right connected to?

Are the grounds on the two power supplies you show floating? If not, what are they referenced to?

What are the voltages in your table measured relative to?

What are points of each measurement in your table? You have 3.3V- listed. Which wire in your diagram is that? Same for the others.

well, complete schematic:



measurement:

 

The question makes no sense at all!! Why is the TS even asking "where is the 110 volts AC coming from??
Is some power supply providing voltage without the mains power connected??Why does the TS believe power is present some place??