Blinking LCD

Hi,

I am new to 3d printing and inherited an old selfmade printer with Arduino 2560 and Ramps 1.4. I updated the Marlin firmware to the latest stable version and more or less got everything running with the following exceptions:

• The LCD - RepRap Smart controller - is displaying Text correctly and shows the menus, but it is constantly alternating between the first menupoint and its contents (like blinking). It appears as if the encoder button would be constantly pressed. I assume that either the encoder is faulty, or there must be a short circuit somewhere. However, I could not find schematics for the controller to carry out educated probing of the board.
  Of course, I configured it in configuration.h, but what also caught my attention is that after booting the kill switch was always activated and I had to deactivate the kill switch in the pins_ramps.h for that controller assigning it to pin -1. Another thing is that the reset button does not seem to work.
  I shielded the connecting cables, so that should not be a problem.
• When I first connected the board, the temperature was correctly given for the heatbed. However at one point it went up to 330 ºC without the bed being heated. The previous owner had the kit mounted on a metal screw passing through both boards, so I guess it shorted. Anyway, I mounted it on plastic standoffs to remove the issue.
  Now the issue is that after updating the firmware and loosing the previous settings, I don't seem to be able to find the correct thermistor setting for the bed. None of the available options gives a correct value and the temperatures displayed for the bed by M105 are fluctuating a lot, while the temp reading for the extruder is rock solid. Also, if I remove the thermistor plug for the extruder, the reading reduces to -15ºC. If I do the same for the bed sensor, the reading does not change, but remains at the last read value. Connecting the bed thermistor to the extruder input pins on the board, I get the correct values for room temperature, which tells me that the thermistor setting assigned to the extruder thermistor ("1") should be correct also for the bed sensor. However, if I assign thermistor "1" to the bed pins, the output changes to 90ºC
  I also tried to assign "0" and the experimental value for 25ºC to the bed input. Both return the correct values.

Any ideas about what could be the reason? Is there any reference for testing the board for short circuits? I inspected the solder joints, cleaned it for removing any residual flux, etc. Everything checks out fine, but the above mentioned issues.

Thanks
Berthold

Sounds like that ADC on the mega is damaged...

Try moving the bed to T2 (change the pins numbers in pins_ramps.h and move the plug)

ramps schematics [reprap.org]
lcd schematics are the same as these [www.sintron.co.uk]

Quote
Dust
Sounds like that ADC on the mega is damaged...

Try moving the bed to T2 (change the pins numbers in pins_ramps.h and move the plug)

ramps schematics [reprap.org]
lcd schematics are the same as these [www.sintron.co.uk]

Hi,
I tried that, but no change. You are referring to this, true?

#define TEMP_0_PIN         13   // Analog Input 13
#define TEMP_1_PIN         15   // Analog Input 15
#define TEMP_BED_PIN       14   // Analog Input 14

If I measure Voltage at the board pins with only USB power connected, I get:

TEMP_0_PIN 5V
TEMP_1_PIN 0V
TEMP_BED_PIN 0V

Are C1,C5,C8 related to those inputs?

Thanks
Berthold

Edited 1 time(s). Last edit at 04/08/2018 09:23AM by beastro.

As for the "blinking" menu and the not working KILL and RESET:

Are you sure that your EXP2 cable is not somehow rotated 180 degrees on one or the other side?

Are the two 10-pin cables identical with regards to the position of the connector locks?

There are different versions of cables, controllers and adapters, as to the position of the connector locks, so that a wrong 180 deg rotation of the EXP2 cable could cause the kill, reset and encoder pins to be wrongly connected (and also the SD card would not function, as its signals are also on that connector).

Below is a schematic of the RRD smart controller, so you might want to check the connection of the EXP2 cable:

Quote
enif
As for the "blinking" menu and the not working KILL and RESET:

Are you sure that your EXP2 cable is not somehow rotated 180 degrees on one or the other side?

Are the two 10-pin cables identical with regards to the position of the connector locks?

There are different versions of cables, controllers and adapters, as to the position of the connector locks, so that a wrong 180 deg rotation of the EXP2 cable could cause the kill, reset and encoder pins to be wrongly connected (and also the SD card would not function, as its signals are also on that connector).

Below is a schematic of the RRD smart controller, so you might want to check the connection of the EXP2 cable:

Hi,

yes, I am positive about the connection... I triple checked the pins.
Also, the SD card is recognized, which wouldn't be the case with inverted cables.

regards