Printer electronics tripping out my computer?????

Hey,
So ive got a massive problem with my printer, it was working fine for ages, i ran a 7 hour print which it finished fine, i switched the printer off and went to work, when i returned from work i connected the mega to my laptop, the electronics lit up as they should as did the LCD, however, when i switched on the main power (12v 30amp psu) the laptop cut out and went off and the printer LCD went bright with blocks on it instead of text. Its almost as if somehow the printer is pushing power through the usb to the laptop causing it to cut out.
Every time it does this i have to wait for the laptop to reset itself by removing the battery and waiting abit. ive tried connecting to my other computer with a different usb cable and it still happens. Theres no signs of damage/burning on the ramps/arduino nor is there any smoke or unusual sounds. im totally stumped

Its worth mentioning that the 5v regulator on the mega popped ages ago, but i managed to get around this by removing one of the diodes from the ramps which allowed the mega to be powered from the usb.

I have a spare ramps but id have to remove the same diode to be able to test it but im worried if theres something wrong with the mega it might damage my spare ramps or perhaps damage my computer

i really hope theres someone out there who can help me as my printer is now a giant paperweight as it is

Measure the voltages on the USB, without the pc connected, but with the PSU turned on. There should be none if you have removed the diode in the RAMPS.

Also check for shorts on the USB, specifically shorts on the USB power lines.



After is had an Arduino board literally go up in smoke, because the 12v power supply delivered so much power to it, when it must have had a fault, I also disconnect the diode on the RAMPS

But I found it very hard to get the diode out, so I used the old trick of cutting the track on the pcb with a sharp knife.
If you need to reconnect it, you just solder a small bit of wire on the underside of the board. It's known as cut and strap in the trade.

Before i disconnected the diode i also found that the arduino was feeding power back into my laptop, which caused the power light led to light up, which didn't seem a good idea to me.

I'm not sure if you are supposed to run an arduino on external power when its also connected via USB.

When I installed the stepper drivers backwards, it had that same affect, nothing but blocks on the lcd. The ramps was fine, but the arduino mega was toast..... Tried with a new Arduino mega and all was right (after correcly installing the stepper drivers...).

Thanks for your replies
I measured the usb without the computer connected and there was 0.61v being produced, wouldnt have thought that would have been enough to knock the laptop out but obviously it was. This does seem to point to faulty arduino, really confusing that it was working fine and suddenly died, im concerned that if i buy another arduino then the ramps might blow the mega's regulator again, i do have another ramps but its from the same place as the one im using now, not sure which way to jump with this

ow and ive noticed that when i connected power to the ramps a blue LED lights up, however, now it comes on blue for a second then goes off and a red LED comes on, not sure if its important but thought id mention it

One very easy way to get voltage back into the computer is a grounding issue. If your +12V supply does not share a solid ground with the computer chassis, they can get a bit off from each other. Since your printer runs current down the negative lead towards the power supply this can drift as the printer does this and that.

Well having removed all the electronics from the printer and plugging the mega into the computer on its own and the computer saying that the usb device is not recognised it seems that somehow the arduino has popped

If the USB regulator has gone, then the Mega won't power off of USB.

The clone Mega boards from China via eBay seem to work as well as any. They are cheap enough that you might consider getting a spare when you order the replacement.

ah i didnt realise that, so the only way the arduino can get power is via the ramps with the diode removed? when i connect power to the ramps with the arduino connected only, theres no lights on the ramps at all, ive heard some horror stories about cheap mega's,ive seen the freaduino mega, supposed to be better than standard ones cos it can handle more amps through 5v regulator

quick question, how do i know if the ramps is working? i know theres power going into it, but how do i know if the board itself works? since the arduino's regulator has blown, and it gets its power from the ramps, then if the ramps isnt getting the power to the whole board then it will never work, is there some part of the ramps i can test with a multimeter to ensure its working? the reason why ive thought of this is that the fault has changed, it doesnt trip the computer out now, theres no lights on the ramps, but ive removed anything except the ramps, mega and lcd and the only life i get out of it is when i connect the usb power, then the lcd comes on but the computer doesnt recognise it, so im unsure now if its the mega or the ramps

Basic power running around on a Mega board (just the Mega no ramps):

1) Plug in the USB cable only and it will try to pull power via USB. It's a 5V CPU and USB is 5V. There's not a lot there to blow, but things do happen. On boards with 3.3 V "stuff" there is indeed a regulator.
2) Plug in a wall wart that puts out +9V and only the wall wart. The regulator on the board converts that to 5V, that powers the Mega chip

With a Ramps, there's a diode that (if installed) routes the +12 to the input of the regulator that would normally see power from the wall wart. You have the same basic cases as above only with the Ramps acting as an auxiliary supply.

What's on a Ramps:

1) a bunch of sockets
2) a bunch of pcb traces
3) some bypass caps.
4) some pull up and pull down resistors

none of that is normally considered to be very fragile

5) the diode that runs power over to the Mega. Short it out and it will blow out.
6) the diode that does reverse protection on the supply (reverse it at high current and it will blow out).
7) the Mosfets. (short them to the supply and they can be blown).
8) the fuses. (when they blow they normally crack wide open).

All of that stuff is pretty much "works or does not work". If you have a meter that will check diodes, test the diodes. The fuses should show very low ohms. The MOSFETS can be tested, the easy test is to look for the crater in the package from when they melted down.

The fragile item in the system are the stepper modules on the Ramps. I know of no easy way to fully check them out without actually trying to run them.

A replacement Ramps 1.4 is in the $18 to 19 full delivered price from your choice of several sellers on eBay. About the price of a stepper motor. Half the price of a spool of good filament. I'd put it in the category of "cheap enough to buy a spare".

Thanks for the reply uncle_bob, ive ordered another mega since the one i have isnt seen by the computer anymore and when it arrives i will use it with my spare ramps, i am abit worried that it will blow the 5v regulator again, is there anyway i can help prevent this?

The 5V regulator on the Mega is a fairly low power part. You can't pull amps off of the 5V supply. It *should* shut down to protect it's self. It *should* be ok to 20V on it's input. The one thing that will kill stuff fast - getting the +12 shorted to a +5 pin on the Mega or the Ramps. There's no real protection against that and it will fry stuff quickly. Simple solution - don't do that.

On the PC side, the USB port *should* ground things together when you plug in. Broken ports / connectors on the PC (or mega), broken cables, blown ports, will all defeat this protection. One real easy way to break a USB that way - give the cord a good yank while it's plugged in. You may break the ground return before you mess up the signal leads. Stuff almost works fine..... Simple check - does your USB on the PC wiggle when you push on it?

Any electronic / electrical system is only as good as it's grounding. Double check all the ground wires in the system, tug on them, check the voltage with a DVM. Put a ground strap on the frame of your printer. If you have an industrial supply, make sure the minus side of the supply has a jumper to ground. Make sure your wall outlet is safely grounded. A little three light plug in ground tester is a dirt cheap way to save your life.

At least around here, it's getting to the dry season. That means more static and more ESD. You can get right into the heart of the electronics on most of these designs. They aren't set up for major discharge to all of those pins. If you are going into the electonics, ground yourself first. Wrist straps are one way, there are other much less exotic ways (touch ground first ...). Don't set things up so you zap the electronics every time you do anything (wires dressed out of the way ...).

Update:
I replaced the arduino mega and used it with my spare ramps and its all okay now, not surprising really since ive replaced the main electronics lol and theres no voltage feedback overloading my laptop. thanks everyone for you help

Mega's are cheap enough at auction that having a spare around isn't that crazy a thing to do.