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Topic: weird symbols appear on my LCD screen (Read 639 times) previous topic - next topic


Jul 01, 2020, 11:44 pm Last Edit: Jul 18, 2020, 11:21 am by Paul__B

Well, that looks fairly straightforward.  Powering it via USB, operating the servomotor for any significant duration may cause the "polyswitch" on the UNO to shut down, but the problem seems to be more related to impulses generated by the relay.

A 1 mF (one millifarad or 1000 microfarad) capacitor across the 5 V and ground on the relay module itself or a 220 µF capacitor across pins 1 and 2 on the LCD (or both!) would be worth trying.  :smiley-lol:

Beyond that, it would require alternate power supply arrangements - a regulated 5 V power supply of some sort (such as a USB "phone charger" rated at 2.1 A) with certain wiring arrangements.

It is most important that the mains wiring to the relay is bundled together so it forms no open loops and is kept away from all other wiring and all wiring is bundled together as it runs from one part to another, keeping 5 V, ground and signal wires as a bundle.


Right now i don't have any capacitor but i've found a power supply that is perfect.
I've wired the "+" with the 5v of the relay module and the servomotor(it was a bit "laggy" and now with the power supply it is smooth), and the "-" with the ground of arduino.
it is working fine but the error is still there (maybe it is less frequent).
do you think some capacitors could actually solve the problem?


It was the same problem with me. I was using the LCD without a petentiometer and I used a temperature sensor with it. It showed weird symbols. But, when the sensor was removed, everything worked fine ( no weird characters ). So my suggestion would be to remove everything and just keep the LCD connected to the arduino.
Success lies within hard work.


unfortunately for my project i need the lcd screen and a sensor for humidity and temperature, i ordered a DTH22 a few weeks ago but it is still on shipment, it is a more precise sensor but i don't know if it will solve this problem.


a 100 uF capacitor on the first two pins of the screen didn't solve the problem, i'll try with a bigger one


i've read on an old forum that maybe separating the ground of the relay module and the servomotor from the ground of the arduino can reduce the interference but i don't know how to do it, if i connect them to the ground of the power supply the relay and the motor go crazy.

what i don't understand is how also the serial monitor stop working...


You may want to use a potentiometer attached to your lcd or an external power sourece for 5v and gnd. Digital pins can be used from the board itself
Success lies within hard work.

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