12864 Smart LCD with RAMPS 1.4 Strange behavior.

Hello,
I received my 12864 LCD screen and tried to hook it up to the RAMPS board. I plug in the USB cable to PC and the screen turns on, shows all the info. If i turn on the 12V power supply for ramps the screen dimms a bit.
The strangest part is when i disconect the usb from my pc and the screen just stays lid, no info showing. Plug in back the usb and the screen shows all the info, just a bit dimmed.
So if a want to see the information on the screen, i have to be connected to my pc. Strange..
I made a video showing this behavior.

Can anyone help me to fix this? Whats the point to have a lcd screen with sd card reader if i still need to be connected to a pc.
Thank you in advance

Looks like you blew the voltage regulator on the mega. I am guessing you plugged the end stops backwards...... Either that or your ramps is not making proper contact.

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End stops connected corectly. its a new printer build, didint print anything yet. all the axis goes home fine.
If the ramps would not make a proper contact, then i think the screen wouldnt show anything on the lcd all the time. Now when i plug the usb to the pc, the lcd shows all the info, i can control everything from the lcd.
No PC - no LCD

Have you installed the Diode (D1) underneath the X and Y axis Driver boards (It is half under each of them)? It is this that allows a 5V feed to the Mega when the USB Is disconnected.

Quote
AuriuX
End stops connected corectly. its a new printer build, didint print anything yet. all the axis goes home fine.
If the ramps would not make a proper contact, then i think the screen wouldnt show anything on the lcd all the time. Now when i plug the usb to the pc, the lcd shows all the info, i can control everything from the lcd.
No PC - no LCD

NO PC = NO LCD as the LCD and ramps are powered by the PC. One of the functions of USB is to provide power. I had the same issue, I am sure the backlight of the lcd is lit but no text is present when the PC is unplugged. This means the ramps board is not getting power, but the LCD backlight is powered by the ramps and not by the mega. I managed to fry the voltage regulator on my ramps when I shorted vcc to 12v vs vcc to ground. If you search end stop issues you see what I mean. Or you can head over to my blog and look at the heading "failure is always an option"

To me it sounds like you either fried the Mega voltage regulator or it was a dud to begin with. There are ways of bypassing this or repairing it as well.

Edited 1 time(s). Last edit at 10/30/2014 11:33AM by jaguarking11.

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Quote
dougal1957
Have you installed the Diode (D1) underneath the X and Y axis Driver boards (It is half under each of them)? It is this that allows a 5V feed to the Mega when the USB Is disconnected.

Will check the board for a D1 diode when i come home. Hope i find no diode there, just an empty space.

This is a pic to show where it is Most ramps as far as I know come without it installed and it is usually taped to it somewhere. If it isn't there then it should be a 1N4004



See Also Ramps1.4 Wiki page

Quote
AuriuX

Quote
dougal1957
Have you installed the Diode (D1) underneath the X and Y axis Driver boards (It is half under each of them)? It is this that allows a 5V feed to the Mega when the USB Is disconnected.

Will check the board for a D1 diode when i come home. Hope i find no diode there, just an empty space.

I checked my ramps board and the D1 diode is in place. So its not diode that is cousing this. Unlless the diode is bad, but i dont think that could be the case in the new ramps board.

There have been a bunch of new boards that the connction from the end of the diode to the mega pin is broken.

With a multimeter check you have connection from the left most leg of the diode to the vin pin on the mega

Quote
Dust
There have been a bunch of new boards that the connction from the end of the diode to the mega pin is broken.

With a multimeter check you have connection from the left most leg of the diode to the vin pin on the mega

Will check the connection of them in the evening. The left leg should be with the vertical line on the diode?

The connection between the diode and the vin pin is great. Could it be that the LCD itself is bad or damaged?

Please check 1117-5.0 on MEGA 2560 board, may mistake 1117-3.3. I English is poor, sorry!

Quote
cxandy
Please check 1117-5.0 on MEGA 2560 board, may mistake 1117-3.3. I English is poor, sorry!

Sorry can you be more specific? What is 1117-3.3?

It's a regulator device like a transistor (3 leads on side, 4th lead is the tab).

There's a bunch of variants, and one is 5.0 (5V) and the other is 3.3 (3.3V).

On a Mega, it's usually between the barrel connector and the USB socket.

Quote
Cefiar
It's a regulator device like a transistor (3 leads on side, 4th lead is the tab).

There's a bunch of variants, and one is 5.0 (5V) and the other is 3.3 (3.3V).

On a Mega, it's usually between the barrel connector and the USB socket.

Cefiar is correct.

My friend ordered lcd for himself, so i think i will wait when he receives it and will check with other one. Maybe its not my board, maybe its the lcd itself thats cousing the problems?

Update. I meassured 5V on the all the servos and aux pins. With 12V power supply i have 3.8V on the 5V pins, with only the USB cable i have everywhere 5V, if i connect both USB and 12V Power supply i have 4.5V on the 5V pins.
Something is wrong with 5V from the ramps board.

Probably mega's voltage regulator is faulty.

The Mega's voltage regulator is very likely working but overheating due to the current drain and going into thermal limiting mode. In particular, the back light on the 12864 needs quite a lot of current. Also, some 12864 displays have the back light series resistor built in, while others need an external series resistor.

I recommend driving the back light through a suitably large series resistor from the 12V supply, so that it doesn't add to the power dissipation in the 5V regulator. From memory, I think the backlight of a 12864 is rated at 100mA and it drops a little less than 4V. So a 100 ohm 1W series resistor should be about right. Or about 200 ohm 0.5W if you are OK with lower brightness.

Edited 1 time(s). Last edit at 11/18/2014 03:05PM by dc42.

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Quote
dc42
The Mega's voltage regulator is very likely working but overheating due to the current drain and going into thermal limiting mode. In particular, the back light on the 12864 needs quite a lot of current. Also, some 12864 displays have the back light series resistor built in, while others need an external series resistor.

I recommend driving the back light through a suitably large series resistor from the 12V supply, so that it doesn't add to the power dissipation in the 5V regulator. From memory, I think the backlight of a 12864 is rated at 100mA and it drops a little less than 4V. So a 100 ohm 1W series resistor should be about right. Or about 200 ohm 0.5W if you are OK with lower brightness.

I meassured the voltages without 12864 lcd, and its all the same. WIthout USB cable conected to the pc, only with 12V power supply i have 3.8V on the 5V pins.
When i connect only the USB, with no power supply i have nice 5V everywhere. It looks like ramps boards is the problem here.

Measure if Mega actually is getting ~12V to it's Vin, although it is probably cheap ass chinese voltage regulator.

As well as measuring the input voltage to the Mega, put your finger on the voltage regulator. If it is too hot to keep your finger on for a few seconds, then it is very likely being overloaded - in which case, check what else you are powering from the 5V rail. If it is cool and being fed with 12V but producing only 3.8V output, then it is faulty or there is a bad connection somewhere.

Edited 1 time(s). Last edit at 11/19/2014 06:56PM by dc42.

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Hi
This is my first post hire and first problem

I bought 12864 graphics smart controller and i have little problem with it.
After change in configuration file (Marlin V1 new) screen is working.
Problem is when press click-encoder its enter next screen but if I want to scroll thru menu its reset (turn off and on by every step).

Is it someone have similar problem or can help me have to solve it.

I tried to touch all of the mosfets. One of them is burning hot, i cannot hold my firnger even for one second to it. i disconected the lcd from the ramps and the mosfet in tha same burning hot. Cant hold my finger to it. What should i do? Contact my board seller? Its a new board.

Which device is too hot to touch? Is it on the RAMPS board or the Arduino board?

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

Voltage controller is on Mega board. RAMPS itself do not have any voltage regulators it only feeds 12V through D1 to Vin pin on Mega. Mega can be powered form USB or external power supply, but if you have connected both it takes power from external power supply and uses on board 5V regulator to step down 12V to 5V.

One other way to test if voltage regulator is working alright is to disconnect Mega from RAMPS then feed 12V to Vin or DC input jack, then measure its 5V rail. If it can not produce 5V then voltage regulator is toast. If it reads 5V try loading 5V rail with simple resistor, I would not try to pull more than 500mA (V=I*R, so for 500mA 5V/0.5A=10Omh;2.5W resitor.) If it can handle the load then RAMPS board is causing problems not Meaga.

As for mosfet overheating, which one and what have you connected to RAMPS board?

Will try to measure the 5V voltage regulator.
As for mosfets, the Q3 one is burning hot.

Q3 on the RAMPS drives the output labelled D8. What do you have connected to that output?

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

D8 heatbed
D9 two 40mm fans with separate mechanical on/off switch.
D10 hotend.

If you are running your heated bet that mosfet will get hot. How hot it will get depends on mosfet itself and how much power your heated bed uses. Check what your mosfet's part number is, then form datasheet you could calculate expected temperature rise.

PS. I found a good cdru post about it (http://forums.reprap.org/read.php?13,422091,422183#msg-422183)
"While not really helpful in determining if that board is good or not (I have no idea aside from the title is flat out wrong...it's not a RAMPS board), power dissipation (that 300 watt rating) isn't useful for how you're using it. P(TOT) for that transistor is computed by the (max operating temperature - ambient) / Thermal resistance junction-case max, or (175°C - 25°C)/.5°C/W = 300 W. You're not going to get anywhere near 300 watts out of it with how it's mounted. At that power rating, you'd need a hefty heat sink and possibly active cooling, or only operate it for extremely short periods unless you wanted to free the magic smoke that is contained inside the casing.

For gauging how hot it's going to get, which is the Achilles heal for the reference RAMPS design, you want the R(ds) value to be as low as possible. R(ds) is the resistance between the drain and source, the main path current is flowing. As current increases, the resistor heats up due to that resistance value. That transistor that you linked to has a R(ds) value of .0095 ohms with a max of .011 ohms. The recommended replacement for a RAMPS board TO-220 package is a IRLB8743PBF which comes in at about 1/4 that at .0025 ohms (.0032 ohms max). For the record, the reference RAMPS design calls for a STP55NF06L MOSFET power transistor with a R(ds) of .014 ohms (.018 ohms max).

For the math behind the numbers, presuming typical R(ds) values, 12 volt heated bed and 11 amps current (since most beds run 10-12 amps...):

P = I^2 * R

STP75NF75 - 11 amps^2 * .0095 ohms= 1.1495 watts
IRLB8743PBF - 11 amps^2 * .0025 ohms= .3025 watts
STP55NF06L - 11 amps^2 * .014 ohms = 1.69400 watts

Take each of the numbers above, multiply by 62.5°C/W, and add to an ambient temperature of 25°C. That will give you how hot each transistor will get
STP75NF75 - 1.1495 watts * 62.5 + 25 = 96.84375°C (~206°F)
IRLB8743PBF - .3025 watts * 62.5 + 25 = 43.90625°C (~111°F)
STP55NF06L - 1.69400 watts * 62.5 + 25 = 130.875°C (~276°F)

As you can see, your resistor and the reference design are going to run pretty hot (although within normal spec), while the middle one will run barely warm."

Edited 1 time(s). Last edit at 11/24/2014 08:07AM by Endlane.