Arduino fuse or mosfet getting hot / no display output
January 20, 2017 07:07AM
Hi folks,

I'm pretty new to the RAMPS topics, so please forgive my newbieness in some points smiling smiley

I hooked up my RAMPS shield to an Arduino Mega, powered it via USB and flashed the latest Marlin firmware (no settings made yet).
Additionally I connected a mechanical entstop (X_MIN) and the full graphics LCD.

As soon as I connect both +/- connectors (the green ones on the shield) to a 12V power supply, the fuse or mosfet (I'm not 100% sure which one it is) near the Arduino power input jack gets hot very quickly.
Also, the display lights up, but no output is given.
There is no load on the ramps (stepper drivers installed but no motors connected) except the display.

Is there a reason for the heat-up of the above named components?

Thanks in advance

Edited 1 time(s). Last edit at 01/20/2017 07:10AM by Royce.
Re: Arduino fuse or mosfet getting hot / no display output
January 20, 2017 08:02AM
The hot component sounds like the voltage regulator (its on the mega, not the ramps?)

It indicates you are drawing far to much power

This is commonly cause by plugging you endstops in backwards and shorting +5v to gnd via the endstop switch.

remove the end stops asap, but its already probably to late. Doing this destroys the voltage regulator.

Edited 1 time(s). Last edit at 01/20/2017 08:05AM by Dust.
Re: Arduino fuse or mosfet getting hot / no display output
January 20, 2017 08:14AM
Yes, it's on the mega.
Damn, that doesnt sound good. So I'll probably need a new mega, right?
Re: Arduino fuse or mosfet getting hot / no display output
January 20, 2017 05:38PM
If the display lights up then you haven't necessarily miswired the endstops and shorted out the regulator. The 5v regulator on the Arduino often overheats when driving an LCD. See [reprap.org].



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].
Re: Arduino fuse or mosfet getting hot / no display output
January 21, 2017 03:24AM
Thank you for that good information, dc42.
Unfortunately I don't understand this article 100%.

The voltage regulator WILL overheat when a graphics display is connected and no 5V via USB is provided?
(see " if you power a servo or a graphic LCD from the RAMPS, then you will almost certainly overheat the voltage regulator. The usual symptom is that the system will not work unless it is connected to a PC via USB")
In my case, the regulator also gets hot when 5V from USB and 12V from power supply is attached.
For my knowledge, the voltage regulator should be inactive when 5V via USB is connected.

What can I do to make this run without buying a Taurino or similar?

Thanks in advance

Edited 2 time(s). Last edit at 01/21/2017 03:52AM by Royce.
Re: Arduino fuse or mosfet getting hot / no display output
January 21, 2017 04:34AM
"For my knowledge, the voltage regulator should be inactive when 5V via USB is connected."

This is incorrect

USB power is secondary If there is a power supply to the DC in jack or the VIN pin of the mega (VIN is the way ramps does it) the power supply is fed threw the voltage regulator on the mega and the power from USB is disconnected via a MOSFET.

There is a common issue of over loading the voltage regulator.. particularly with 12864 lcd's

If you think its your problem. Disconnect the lcd, see if the voltage regulator keeps its cool.

Personally I would not run a full graphics LCD on a mega based machine, It takes to much power and eats up to many cpu cycles causing glitches in your prints.

Edited 1 time(s). Last edit at 01/21/2017 04:38AM by Dust.
Re: Arduino fuse or mosfet getting hot / no display output
January 21, 2017 06:41AM
Thanks dust, didnt knew that.
So you think it's better to run the printer without a Display at all?
Re: Arduino fuse or mosfet getting hot / no display output
January 21, 2017 07:30AM
I personally don't use a display, I have played with the main types, a 20x4 char display works fine with mega based controllers.

Many people insist you can't get good prints from a connected computer and say you need to print from SD card.. I prove this wrong every day. (but I do use a dedicated Linux machine)

But I would consider myself a casual user, not running machines 24/7 as a business type thing.
So for me a LCD is a optional luxury.

If you want one, get one.

If you really want the graphical LCD, I would recommend a 32bit controller. (eg: re-arm, duet, duet wifi, smoothieboard, various smoothieboard clones etc,
you would have to look into which supports a GLCD)
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