# LM35 temperature Sensor Problem

#### sa_5ive_2004

Joined Aug 16, 2017
2
Greetings,
I would like to explain my small project to sense the actual temperature of any room using (LM35 Sensor), here below, I will write the tools I have used and the problem I faced. therefore, if there is any useful idea or information that can help me to solve my issue please advise me.

Tools:
2- LM35 temperature sensor
3- 16 * 2 LCD Screen
4- Cat 6 (LAN cable)

My problem:
I want to put "LM35 Temp. sensor with Lilypad board" in one room, and pass the connection cable from Lilypad board to LCD screen by using Cat 6 Cable with a 40M length of cable to another room, I'm sure the cable length is too much long, the result: there is no signal transferred through the cable and all data are dropped. there is any information or idea to solve this problem by using any kind of boosters or any other solutions.

hope to hear answers as soon as possible.

best regards.

#### AlbertHall

Joined Jun 4, 2014
12,331
What signals are you sending to the LCD? I2C?
If so, then there is usually no lower limit to the I2C clock speed so you could try running the I2C more slowly.

#### sa_5ive_2004

Joined Aug 16, 2017
2
What signals are you sending to the LCD? I2C?
If so, then there is usually no lower limit to the I2C clock speed so you could try running the I2C more slowly.

thanks a lot for your quick answer, but actually I'm not using i2c module.
if i will use it, i2c will solve the problem of long length ???
regards.

#### jayanthd

Joined Jul 4, 2015
945
thanks a lot for your quick answer, but actually I'm not using i2c module.
if i will use it, i2c will solve the problem of long length ???
regards.
You can't use a 40 mtr cable for Parallel LCD connections. They work at TTL levels. 15 cm is ok.

I assume HD44780 or compatible Alphanumeric Lcd.

#### shteii01

Joined Feb 19, 2010
4,644
i2c is exact opposite. It was INVENTED for short distances. You can do 1 meter using i2c. If you do some tricks, you can extend that some. There are also i2c extender chips you can use.

#### AlbertHall

Joined Jun 4, 2014
12,331
thanks a lot for your quick answer, but actually I'm not using i2c module.
if i will use it, i2c will solve the problem of long length ???
regards.
So what system are you using to drive the LCD? 4-bit parallel?

#### DickCappels

Joined Aug 21, 2008
10,127
On which end of the cable is the Arduino? We assume it is at the opposite end of the cable from the LCD.

If it is at the opposite end of the LCD, and if the LCD initialization code is write only (the LCD does not have to send data) then maybe a resistor in series with the enable pin is all you need. The falling edge of the enable signal is what latches data into the LCD controller. Actually it could be ringing on the data lines as well. 40 meters means a 240 ns round trip!

The first thing I would try is slowing down the write frequency to the LCD, especially leaving a long time (microseconds) between setting data and taking the enable low and see if that fixes it.

The next step would be to put 1 k resistors on all inputs.

Or if you are lazy like me, you would put a second microcontroller at the LCD and only send power and serial (RS-232 or similar) down the cable.

#### OBW0549

Joined Mar 2, 2015
3,566
Or if you are lazy like me, you would put a second microcontroller at the LCD and only send power and serial (RS-232 or similar) down the cable.
That isn't laziness; it's just good design.

#### AlbertHall

Joined Jun 4, 2014
12,331
Or if you are lazy like me, you would put a second microcontroller at the LCD and only send power and serial (RS-232 or similar) down the cable.
Or, to be certain, RS-485 and power.