Ramps 1.4 current limiting LCD + Servo

Hello,

I have a little problem with my prusa i3 from folgertech.

I just managed (after some problems) to install the auto bed levelling with a 9g servo. Everything works fine, the servo is well connected and the 5V jumper too.

But today, I tried to connect a full lcd graphic to the ramps. And now when the servo moves it makes the lcd flicker a little bit and then put ramps in reset.

I think the problem is about current consumption that is too high for the ramps to handle between these two adds.

I don't know what to do. I have two ideas but don't know if they will work :

- Get 12V from PSU, put a little board with regulator to have 5V with good current from power supply and supply servo's 5V with it. This will avoid servo pulling too much current from ramps regulator.

- Change backlight resistor on smart LCD from 0 ohm to something higher so that the lcd consumption will be smaller.

I want to have your opinions on this problem.


Thank you in advance for reading and answering,

Madcreator

This issue comes up at least once a week on these forums. The 5V regulator on the Arduino can provide very little extra current without overheating. You should not power a servo from it, let alone a graphic LCD as well.

Also, an LCD with only a 0 ohm series resistor on board is intended to be used with an external series resistor.

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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].

Hi thank you for your answer ! I undrstand well where the problem comes from but how do you resolve it ? Do you supply the LCD and servo from external power supply ? Can't I use the 12v of the psu ?

I really searched but didn't found any solution. Even if it appear à lot, every problem is différent.

Madcreator

Quote
madcreator
Hi thank you for your answer ! I undrstand well where the problem comes from but how do you resolve it ? Do you supply the LCD and servo from external power supply ? Can't I use the 12v of the psu ?

I resolve it by using better electronics, which has a 5V switching regulator included on the board. And I don't have a servo, for the Z probe I use one of my own IR sensors instead (see [miscsolutions.wordpress.com]).

Assuming you want to continue using RAMPS, I suggest you add an external 5V regulator and power the whole Arduino/RAMPS 5V rail from it. If you didn't have the servo as well, then a simpler solution would be to power the LCD backlight through a series resistor from 12V, something like 180 ohms 1W.

---

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].

Hi I have the same issue and I was thinking to connect 5V output from LM2596 to the 5V pin on Ramps 1.4 next to the PS_ON pin.

But I am new to the electronics and since the Converter has two leads (+) and (-), I don't know where to connect (-) lead of LM2596.

Is there any suggestions?

Best Regards, Serdar.

Hi !

I have resolved mine with your solution !

So you just need to make the schematic showed in the datasheet of the LM2596. You connect the 12V input to the 12V of your PSU (Power unit fo your reprap).

And you connect the 5V output of the LM2596 to the Servo VDD (instead of putting the jumper you connect the LM2596 output).

The (-) of LM2596 goes on any GND pin of your ramps board.

If you need further help, please provide board reference, but I think you'll make it !