Short circuit fried my laptop!

Hi!

Recently I started building my own 3D printer. I received a motor and RAMPS 1.4, and wanted to try out the stepper motor. This worked great, until the moment that I fried my laptop

What happened?

In attachment you find a small schematic overview of the setup Circuit.pdf.

To program my arduino, I connect it through USB to my laptop. Every time I wanted to do something with the board (eg replace the motor driver), I would disconnect the power from the board. I use a 12V, 5A power supply, which was connected through a breadboard and a switch to the RAMPS 1.4.

I switched on and off the supply to the RAMPS numerous times to change things on the boards, until the moment that a short (?) generated that much current that a jumper burnt through, and my laptop switched off, not to be revived. BTW: the laptop was grounded through its power supply. After inspection, I found that a wire just after the switch had burnt through, but should not have caused a short circuit (was not grounded nor in connection with other conducting surface).

Additionally, I was not able to reprogram the RAMPS 1.4, as the arduino board seemed to have lost USB connection functionality. The board itself seemed to still work.

Heinsight, this might not have been the smartest setup:
- Small wires on breadboard connecting the high current power supply with the RAMPS & motor (Nema 17).
- Switching would result in high currents throughout the system
- The grounding of the laptop was probably better than that of the power supply

My questions:
- How can I avoid such a scenario from happening again? A normal printer would also be connected to the laptop through USB and does not result in a total-loss of the laptop?...
- How can I avoid the high currents through the system at startup (if this is the root cause)? Can I further isolate the motors?
- How to protect the USB interface from any short circuit/high current?
- Is there a way to revive the USB interface on my Arduino Mega 2560 board?

It's been quite a scare... My laptop now is at a shop for inspection, but I'm not really optimistic about its faith.

I would like to continue my queeste to build a 3D printer, but of course, I would first like to know how to avoid disaster like this...

Thanks!

Most USB ports already have some protection on them...

If you draw to much current from a USB it will normally shut down that port (often requires a complete power down to reset)

You say a jumper burnt out? which jumper?

Indeed, I also thought that the USB port would have such protection... It appeared not to be sufficient for this event though... The laptop cannot be restarted anymore, and seems to be dead.

I probably use the wrong word with "jumper", it was just a wire on the breadboard from the switch to the breadboard. That wire burnt through (insulation melted for ~3mm long).

What happened on one power supply I had was we burned up 3 Arduino Megas. What occurred was, inside the power supply one of the power transistors was up against the side wall of the case. This was expected as it was being used as a heat sink, but there was also an electrically insulating material between the transistor and the wall. On this power supply there was a short.

The ground pin on the power supply was connected to the metal chassis. The transistor was also linked, making the + voltage and the ground on the power supply equivalent. This made the Arduino ground -12 V and high at 0 volts. My computer fought that and wanted ground to be 0V and + to be +5V as per USB standards. The result? Burnout on the resistor beside the USB port.

Also, was the Mega official?

In terms of computers getting fried via Arduinos, I have only heard of one guy who put +12V along the ground line by accident.

So, solutions!
1. Check the voltage difference between Ground and + and - on the power supply
2. Use a XBox 360 power supply (There are settings in Sprinter and Marlin for this)

I know. It is hindsight at the moment. Tell your story so others know.

It's definitely interesting to read your suggestions! Only a pitty regarding the circumstances...

The mega was as official as I can see... It has all the "right" inscriptions... I do use a "special" power supply, which I got from AliExpress (similar to this one). As this is still working, I am not looking at it as a source of the problems. However, should I be looking at this as the source? If so, is there any way to confirm where the source of the issue lays?

I definitely want to ensure that I, and others, do not get into this kind of sh*t anymore :-)

I do understand from you that it's not unheard of to keep your computer connected through USB to the Arduino while switching on/off motors etc connected to a RAMPS shield?


As for your solutions:
1. I will check that when I get home :-) and let you know! I remember me checking that in the beginning, but you're right to say that might have changed!
2. I see that you suggest to use an XBox power brick. Is it common people have bad experiences with other power supplies (like the AliExpress one)?

I checked the voltage on my power supply. It's 12.20V between +V and COM. It seems to still work...

Anybody an idea how to revive a Arduino Mega 2560? It is not in device manager and when I plug it in, Windows is not recognizing it. It does still have power as the red light is on while it's connected to the PC... Maybe there's something I can check with a multimeter to check if the board is broken or not?

Thanks!

I use an XBox 360 power supply on mine. I never did get the auto power on/off to work on it though. The fan on it is very loud. I used it because I had one laying around and didn't want to spend money on a new one during all the other expenses with building a printer.

I'd like to replace it with a more basic power supply like this one:

[www.ebay.com]

But it does have some added risk in that the power connectors are more exposed. But it's quiet.

---

E. J. Bantz
[3dprintercamp.com]

Indeed, I use such a power supply, to be precise it's this one. Actually, I think it's quite OK, and not the source of my troubles. Still need to determine how much power I exactly need for my 3D printer, but 5A should do for now, I guess