USB power connected at the same time as Patch powered up

Eurorack
1

Hello,

Just got a used patch, and got OOPSY working last night. So cool!. When I powered down my eurorack case, I noticed that the module was still powered via the USB connection. In the world of Teensy modules, like ornament and crime, we cut the 5V trace so that you don’t connect power supplies together. Should I worry that I’m connecting my USB power directly to a 5V regulator on the Patch? Doesn’t seem good. Should I cut a trace somewhere?

2

No trace-cutting needed. Daisy Seed is designed to safely handle power coming in USB and the Vin pin at the same time.

3

Thanks. I’m not worried about the $21 seed - I’m worried about oscillations due to imbalanced impedances damaging my $350 eurorack power supply and my computer’s USB port.

4

I haven’t heard of anything like that with Daisy.

5

If you feel you can’t accept ElectroSmith’s reassurance and ‘Don’t worry’ (and I must admit I’d feel the same way), you can ‘cut the trace’ in the USB cable, the +5V line, often the red wire. Just be sure to label that cable!

1 Like
6

I’ve seen posts from Paul Stoffregen explaining why he designed Teensy without diodes to handle simultaneous power from USB and the Vin, but he also suggests diodes if desired, to control direction of current flow when two different sources are supplied, and tells of minimal consequences from accidental power on both inputs.

Daisy Seed has diodes, to prevent current flow in the wrong direction, and Patch powers seed using a 24v to 5v isolator powered by eurorack +12 and -12 supplies.

I’d like to read more about the effects of imbalanced impedances and oscillations.