How to send LCD output to Arduino?

Hi All,

I have a RPM speed meter ( and the output of the senor is shown on a LCD. I can see four pins (+5V, GND, Rx, Tx) on the LCD (red box in image below). I am wondering how can I send the LCD output to Arduino (for example print the data on Arduino serial monitor)?

Thank you for your help in advance.


Usually sending data from an LCD is not supported. However those two pins, Rx and Tx, are interesting.
Do You have access to an oscilloscope so You can have a look at the Tx?
Try to get hold of technical documentation for the unit....

Why do you think these are "outputs"? RX is usually an input.

Why not just sample the tachometer signal from the fan directly, using an Arduino input? It's been done successfully by hundreds or thousands of people.

Hi Railroader,

Thank you for your reply. It seems reading data from LCD it is not possible or complicated, so I am going to read the signal from the sensor.

I thought so too but didn't want to show off.....

Hi jremington,

Thank you for your reply. I thought since the LCD had RX and TX, these are pins to receive and transmit data.

Hi aarg,

Thank you for your reply. Since the LCD directly shows RPM, I was wondering I can directly read the data from LCD.

I found the code from the link below to read rpm from a hall effect sensor (similar as mine), do you think will it be useful for my application?

Sure, but what data?

The sensor you linked does not have an LCD. It has a seven segment LED display.


Oh, I am sorry. You are right, it is a LED.
I mean the data shown on LED which is rotational speed in rpm.

Ask the seller about the purpose of those connections.

An oscilloscope or logic analyzer might reveal something interesting on TX.

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