I have made a board as shown in the circuit diagram. There is no connection from 5 volts to either VIN or 5v pins on the Nano, but it runs happily without the USB connection. Is it possible that enough power flows through pin 10 (via SW1) for it to run?
(Note that I have forgotten to show the large capacitor across the 12v supply, and may have drawn the laser diode upside down)
Never have a powered circuit connected to an un-powered Arduino. Bad thing are sure to happen.
is it possible that enough power flows through pin 10 (via SW1) for it to run?
Yes.
Through that switch then through the 8825s and Reciever and though all the connections to the Nano I/O pins and that is NOT good
@jim-p Thank you - I will desist. Because my onboard buck regulator produces nearer to 5v than the USB does by a very small amount, I hope it is safe to connect both simultaneously (as when updating the sketch).
Which Nano?
There are several models now and it may not be safe
It shows in IDE as ATmega328 MiniCore, variant 328PB and it has an FTDI usb chip. Forgive me this answer is meaningless.
No, it means quite a lot.
It's some kind of clone and I'm not sure of a safe way to power it.
Just to be safe I would NOT connect power to the 5V pin and have USB connected at the same time.
You may consider connecting the 12V to Vin if it is indeed rated for 12V.
Thank you. I can easily de-power it prior to uploading. Is USB and 12v through the onboard regulator safe for proper Nanos because there is built in detection of duplicate supplies?
Again which ones?
Ther are several and the power schemes are different.
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