Does Axoloti draw power from USB(via computer) or the PSU, if both are connected?

#1

Hey

Was wondering how Axoloti works if it is connected both via USB device port to a computer and it has also a PSU connected? If this is possible at all, where will the Axoloti draw its power from?

Thanks!

#2

Short answer:
If the DC jack is connected it will get it's power from the DC power supply rather than the USB.

Long answer:
Take a look at the schematic.
DC Side
USB Side
The enable pin of both devices is connected to signal VBUSEND derived from the unregulated DC power input, but the enables have different polarities. ie- when DC power is provided the USB power will be switched off.

#3

if you input DC power through X2 instead of the DC Jack, does this safety mechanism still work? (seems like it does but don't want to take any chances!)

(i'm boxing 2 axolotis and sharing a single DC power socket on the case to the two X2s)

#4

In doubt, insert two current meters and test what power it draws from either connection. But provided that all sources are well-isolated clean DC power supplies, it should not matter whether there are multiple supplies - in parallel, the voltages do not add up (or change otherwise), and the added potentially available current is absolutely harmless (that is, irrelevant if the supply already exceeds the demand, beneficial if there was a power shortage) in a voltage-constrained device like the Axoloti. The automatic isolation between USB and the power input is there to enable you to use a external power source to work around the widespread unclean USB power issues.

#5

X2-2 (on the schematic) is the same as the X1 (the unregulated DC input) - so the same USB/DC power switching mechanism applies.

#6

thanks - also might be best to join the 2 axos at the 5 pin break between the DIN PSU and the boards and just power one DIN PSU
.... decisions decisions!