GT2560 Rev A+ Power over USB

[Sp8ter]

Hi,
I have the Geeetech Prusa I3 Pro B and im realy happe with it.
A few days ago i bought the 3D Touchsensor for it, installed it and flashed the firmware for the GT2560 Rev A+... Everything works!

The only thing im not happy with is, that if i shut off the power via powerswitch, the display, touchsensor and board are not shutting down.
They are still powered by the USB Power. With the old firmware everything shut down when switching off power.

Is there a way to change that behavior in firmware?

[William]

Could you tell me which two versions of firmware you are using?
I want to try

[Sp8ter]

Hi William,
thanks for you help :D but i think i found the error...
I have 2 Boards and while i installed the 3d touch sensor i swapped the board because one of the clamps was broken.
The first Board has no power on USB and the second has, firmware doesnt matter...
I think one of the USB power-connections must be broken on my first board.

Now im considering to just cut the power cables of the USB Cable of the new board to have the same effect on it.

Do you think that would work?
If there is a solution in Firmware i would prefer that but i coulndt find anything.

[William]

I think you are correct

[1138]

I can confirm that both the GT2560-A+ board and the LCD are kept on if the USB is connected to a powered on device (say PC, notebook). No matter is the general switch in the printer is turned on or off. This is independent from the firmware versions I have tried: the "factory" one, 1.1.14 (https://www.geeetech.com/forum/viewtopic.php?t=19846) and bugfix-1.1.x (which is 1.1.8 ATM).

My approach is to use a USB extension cable and a double circuit switch to turn the USB connection on/off.

[JustinSB]

This was covered a couple of weeks ago in the "Geeetech 3D Printers Owners Group (Unofficial)" on Facebook. You're going to kick yourself when you read the solution, but for starters I would advise against trying to cut the power in a USB cable as it's a complete nightmare. However, to sort the power backfeed from the USB, all you need is some bog standard electrical tape. Cut a small strip about a couple of mm wide by around 2 cm long, & carefully stick it over the power connector inside the rectangular USB plug, then bend it round & stick the rest to the outside. Carefully plug it in, & you should be laughing! That's it, job done. I nearly fell off my chair when I read about it, as it's been bugging me for months.

For the record, the VCC pinout in the USB A Type cable plug (ie the power) is the one on far right, when you have the rectangular plastic bit at the bottom as you look at it. You shouldn't disconnect the ground, so you only need to do this on the one pin.

[1138]

[quote=JustinSB post_id=82567 time=1518466695 user_id=62140]
This was covered a couple of weeks ago in the "Geeetech 3D Printers Owners Group (Unofficial)" on Facebook. You're going to kick yourself when you read the solution, but for starters I would advise against trying to cut the power in a USB cable as it's a complete nightmare. However, to sort the power backfeed from the USB, all you need is some bog standard electrical tape. Cut a small strip about a couple of mm wide by around 2 cm long, & carefully stick it over the power connector inside the rectangular USB plug, then bend it round & stick the rest to the outside. Carefully plug it in, & you should be laughing! That's it, job done. I nearly fell off my chair when I read about it, as it's been bugging me for months.

For the record, the VCC pinout in the USB A Type cable plug (ie the power) is the one on far right, when you have the rectangular plastic bit at the bottom as you look at it. You shouldn't disconnect the ground, so you only need to do this on the one pin.
[/quote]

Is it "safe" to have the VCC pin "cut" (even if it is done with tape) but not the data lines? Will the electronics be affected if a (long) signal is received while being unpowered?

[JustinSB]

My GT2560A+ board doesn't appear to care that it doesn't have USB power, as it gets its power from the PSU. The guy on FaceBook who wrote about the idea said that he's been running his printer like this for the past year with no adverse effects, & many people online appear to have actually managed to physically cut the power line in their cables. It goes against the USB protocol specs, but this doesn't appear to matter to 3D printers.

The USB circuits get back-powered from the 3D printer PSU as it powers up the board, & everything on my systems connect quite happily.

If it's not powered, then it's not powered. No signals will ever get a response because it's turned off.

[_kaktus_]

Personally, I think that one diode on the PCB would definitively solve the problem of power supply from two sources.
But it is at the discretion of the producer.

[biotech]

Hi,

I think I've found the issue.

I have two REV.A+ Boards, one is acting ok (no 5v. out fron USB), the other one
has the problem.

Checking the boards deeply, I noticed the board with issue has a 0 ohm resistor
near the USB connector, which makes the 5v. flow form the board to the USB cable.

I've attached two photos:

https://www.dropbox.com/s/v4obla336lfm9 ... 4.jpg?dl=0
https://www.dropbox.com/s/5gdiyk6uk3sr3 ... 5.jpg?dl=0

So, desoldering that resistor would fix the problem.

Bye!