Ramps power through one terminal!

Afternoon! I have problems.... Last 4 months I've been building a 3d printer from scratch, never done it before. Managed to finish assembling and now actually testing.

Using Ramps 1.4, Marlin firmware.

Video of my first print attempt: [youtu.be]

I'm not much of a electronics person - basically LCD display on the ramps is suffering from bright and dark streaks along the screen, melted a bit on one of my Ardunio Mega's and I now have to power it separately from the USB so I presume the 12 volt to 5 volt diode has burnt out?!

Originally I followed a tutorial on using a PC PSU (my case 500 watt), cut the 4 cables CPU power plug and using those wires into the two ramps inputs, 5 Amp and 11 amp, and connected the two wires to turn the PSU on. However subsequent reading turns out the tutorial might not have been correct for wiring it.

Basically the print will print, then cuts out. It also suffers from jerking movements every so often which causes drift.

Applied a volt meter reading amps - the 11 Amp socket on the Ramps takes no draw when heating the hotend. The hot end is being heated through the 5amp, and with the motors running it is 5.03 amps, then when I heat the hot end its exceeding 7 amp draw which it probably causing the jerking motions (the AMPS fluctuate greatly) and the eventual cut out.

My question - why would the hot end be drawing power through the 5 amp connections and not the 11 amps. Could something have burnt out on the board?

Is there a good definitive wiring guide for a PSU so I don't make the same mistake of presumably cooking everything.

The RAMPS is still working, just. Before I replace it, want to either fix and test or at least figure out so I don't blow up another.

Bed is turned on by a Mosfet, slight cock up there as its 12 volt 600 watts so it draws and immense amount of power (my print bed size is 450 x 450).

Any help much appreciated.

Thanks, James

Edited 1 time(s). Last edit at 03/08/2018 06:53AM by PuG.

"why would the hot end be drawing power through the 5 amp connections and not the 11 amps."

because a normal 200x200 bed uses 11amps, nothing extra for a hot end. Only the bed is separated.

The most common cause of a dead voltage regulator on the mega (its on the mega, not the ramps) is a short on the 5v rail. Most commonly a mechanical endstop plugged in backwards. So the switch connects +5v to gnd instead of the Sig to gnd pins.

It not likely you did this with power supply wiring... If you wired it wrong you would have connected +12v to gnd and blown the power supply fuse or the supply itself.

Your bed is far to current hungry
600watts at 12v is 50amps! on a circuit designed for about 11amps.
I suspect the 11amp polyfuse exploded and the connectors melted with that one.
Also powering a 600watt bed on 500watt power supply is never going to work... also some of that wattage on a pc power supply is for non 12v rails.

Although a short from +5V to ground is likely to kill the 5V regulator on the Arduino, it isn't the only cause. Powering a 12864-type LCD display from Arduino/RAMPS often overloads the 5V regulator and causes it to fail after a while.

It sounds to me that you are using a ATX power supply; in which case it may be cutting out when you have a heavy load on the 12V output (the bed heater) if you don't also have a dummy load on the 5V output. This happens with ATX power supplies, especially the cheap ones, because the 5V and 12V rails are regulated as one.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the replies. The bed is not wired in at all direct to the Ramps, realised it wasn't a good idea at the start before even testing it , separate circuit via Mosfet.

I think dc42 your right, I don't have a dummy load on the 5v output.

Just I assumed, the hotend and bed came from the higher 11 amps considering when the motors are going, with the hot end on, the 5A feed is up to 7 odd. Also explains when I first initially did testing at a PLA temperature it worked without cutting out. Built it for mainly PetG.

Will see if I can find a resistor to go on the 5v or something to load it.

Edited 1 time(s). Last edit at 03/08/2018 11:59AM by PuG.

Also take a look at the 5A polyfuse. They are often crap and cause power failure. Replace it with an inline car fuse.

Right, all problems solved! for the moment.

Turns out my fault, I had forgot to adjust some of the stepper driver voltage limit which was causing the fluctuations. Unplugged the LCD as I don't really need it.

Solved my heating bed amp issue, brought in one of my spare tractor batteries

Thank you again for the replies.