Printer powered over USB ?!

Hi all,

Is it normal that when my printer is connected to a computer which is turned on, but disconnected from the power supply a part of the electronic is running ?

The LCD Backlight is on (lights up blue) but no text appears. All endstops are working and also the Arduino is powered. But all fans are disabled and the motors are not reacting to any commands.

I want to get rid of that problem so when the main power supply is not connected the printer is total off and not still a bit powered over usb.

Thanks for help..

You might have to cut a trace on the Arduino.

Both my ramps1.4 show the screen lit with text on them when only powered over usb

It depends on the control board how you switch this off. On a Meltzi there is a jumper you move.
The boards are designed so you can power the controller from USB so you can sort the software out. The USB will only provide limited current - different computers have different limits and the more devises in USB ports the less current you can have. This current is insufficient to do anything mechanical so your motors etc wont move and may not even be wired to this power source. Its also possible that you LCD backlight is drawing to much current and preventing the display driver working. Could be worse as it could be preventing the controller working.
Research your controller for how to configure for 12V power only.
Its normally advisable to be on "12V only" during printing as anything that affects the USB on the computer (sleep mode, other USB devices) can cause the controller to switch off during a print.

Thanks for your answer,

A 12V only mode would be great. I will seach for that.

Quote
GRAYWOLF
Both my ramps1.4 show the screen lit with text on them when only powered over usb

If only visible txt when powered up from USB, and when you plug 12 V there's none, you might have
your board's 5 Regulator out of service on your arching mega.
I'm not that sure, but think I read something liked in the past. Try search a bit from forum.

Cheers

Edited 1 time(s). Last edit at 11/27/2016 02:40AM by Bobyni.