Ramps and display / 5V problems
Posted by Downunder35m
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Ramps and display / 5V problems April 04, 2016 09:06PM |
It seems that more and more people experience problems with their Ramps board when it comes to a stable 5V supply.
As I faced the same problem a while ago and needed to dig really deep through the WWW to find the cause I will sum it sum here for future reference.
Especially the Arduino Mega with a Ramps board V1.4 seems to struggle, mainly when users try to print from the SD for the first time and disconnect the USB cable.
Usual result of this action is a useless display and being unable to print.
Other users report problems with temperature readings especially if heated beds or multiple extruders are used.
So what is the cause of the problem?
In all cases I found the user trusted that the Ramps board will supply the power for the Arduino - which it does up to a certain point.
If you feel the need then check the schematics for the Ramps board and see where the 5V pins connect - and what hangs on them in your system
Long story short:
The Ramps board won't supply the 5V to the Arduino and it won't supply the 5V to the 5V pins for displays and other things either!
Instead you end up with about 3.2-3.8V that is leaking from somewhere.
Adding a 5V supply to a 5V pin won't always help either as a badly regulated and stabilsed 5V will mess even more with everything.
The best solution so far that I found and still use is actually quite simple:
If your main power supply is 12V then add this to the power input of the Arduino and all works as expected as now the Arduino supplies a stable 5V.
If your main power supply is 24V then use a 12V regulator between the 24V rail and the Arduino power input.
I used the later on my laser cutter for quite a while now and the 12V regulator does not even get warm - without a heatsink.
There are some "solutions" posted on the web that include modifications to the Ramps board, stay away from them
With a USB connection you get the 5V from your computer/laptop if the Arduino is not connected to power.
There we have a max of 500mA unless you use a USB3 port.
As the Arduino is designed to be used with multiple power sources for various purposes you can't harm it by supplying 12V while the Ramps board is doing the same.
But you can do damage and get false readings if you use an external 5V source as a substitude.
The problem with displays on a Ramps board...
I use the Reprap Full Graphics Discount Controller (what a name....) and also faced the darkness problem on my machine.
And as I used the display before without a ramps board and no problems at all I suspected the problem to be either there or with the pin assignment in the firmware.
Firmware was fine so the multimeter confirmed I only get a bit over 3V to the controller instead of 5V.
Adding 5V directly to the display solved this but the SD was unusable as it needed the 5V for the onboard 3.3V regulator
It was after this experience that I measured the 5V on the Arduino to find out there is no 5V.
So as above the easy fix was to supply power to Arduino itself instead of just powering it through the Ramps board.
Be aware though that some of these "smart" controllers can't be adjusted in brightness or contrast through the firmware settings or the encoder.
The circuit layout on some boards was simplified to say it as nice as possible.
The contrast is adjusted by a pot that is located on the back of the display itself - impossible to reach without taking the display off.
The pot on the front has no affect at all in most cases and can be ignored if nothing happens.
The brightness is fixed with a resistor.
For those wanting to know why:
The controller uses a serial connection for the display instead of the parallel connection most displays use.
The display itself can be connected in parallel mode as well - you can add a cable to the pins on the board.
A serial connection is prefered as otherwise you would need a massive amount of pins to drive in parallel mode.
It is also the only option to connect it to a Ramps board as there are not enough pins left to use without interfering.
The encoder and beeper need pins and the SD as well.
So one day a guy in china had the great idea to make it simple and gave the display fixed settings without optional jumpers for those who like the orginal design.
The original with the white circuit board should still be fully adjustable, the red and blue china models will be with fixed settings.
As I faced the same problem a while ago and needed to dig really deep through the WWW to find the cause I will sum it sum here for future reference.
Especially the Arduino Mega with a Ramps board V1.4 seems to struggle, mainly when users try to print from the SD for the first time and disconnect the USB cable.
Usual result of this action is a useless display and being unable to print.
Other users report problems with temperature readings especially if heated beds or multiple extruders are used.
So what is the cause of the problem?
In all cases I found the user trusted that the Ramps board will supply the power for the Arduino - which it does up to a certain point.
If you feel the need then check the schematics for the Ramps board and see where the 5V pins connect - and what hangs on them in your system
Long story short:
The Ramps board won't supply the 5V to the Arduino and it won't supply the 5V to the 5V pins for displays and other things either!
Instead you end up with about 3.2-3.8V that is leaking from somewhere.
Adding a 5V supply to a 5V pin won't always help either as a badly regulated and stabilsed 5V will mess even more with everything.
The best solution so far that I found and still use is actually quite simple:
If your main power supply is 12V then add this to the power input of the Arduino and all works as expected as now the Arduino supplies a stable 5V.
If your main power supply is 24V then use a 12V regulator between the 24V rail and the Arduino power input.
I used the later on my laser cutter for quite a while now and the 12V regulator does not even get warm - without a heatsink.
There are some "solutions" posted on the web that include modifications to the Ramps board, stay away from them
With a USB connection you get the 5V from your computer/laptop if the Arduino is not connected to power.
There we have a max of 500mA unless you use a USB3 port.
As the Arduino is designed to be used with multiple power sources for various purposes you can't harm it by supplying 12V while the Ramps board is doing the same.
But you can do damage and get false readings if you use an external 5V source as a substitude.
The problem with displays on a Ramps board...
I use the Reprap Full Graphics Discount Controller (what a name....) and also faced the darkness problem on my machine.
And as I used the display before without a ramps board and no problems at all I suspected the problem to be either there or with the pin assignment in the firmware.
Firmware was fine so the multimeter confirmed I only get a bit over 3V to the controller instead of 5V.
Adding 5V directly to the display solved this but the SD was unusable as it needed the 5V for the onboard 3.3V regulator
It was after this experience that I measured the 5V on the Arduino to find out there is no 5V.
So as above the easy fix was to supply power to Arduino itself instead of just powering it through the Ramps board.
Be aware though that some of these "smart" controllers can't be adjusted in brightness or contrast through the firmware settings or the encoder.
The circuit layout on some boards was simplified to say it as nice as possible.
The contrast is adjusted by a pot that is located on the back of the display itself - impossible to reach without taking the display off.
The pot on the front has no affect at all in most cases and can be ignored if nothing happens.
The brightness is fixed with a resistor.
For those wanting to know why:
The controller uses a serial connection for the display instead of the parallel connection most displays use.
The display itself can be connected in parallel mode as well - you can add a cable to the pins on the board.
A serial connection is prefered as otherwise you would need a massive amount of pins to drive in parallel mode.
It is also the only option to connect it to a Ramps board as there are not enough pins left to use without interfering.
The encoder and beeper need pins and the SD as well.
So one day a guy in china had the great idea to make it simple and gave the display fixed settings without optional jumpers for those who like the orginal design.
The original with the white circuit board should still be fully adjustable, the red and blue china models will be with fixed settings.
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