Arduino LCD TFT Blackout after 15 minutes

[ammaralroz]

Hi.

I need help with my project. I will provide as many details. I have Arduino mega reading the temperature from 14 sensor DS18B20 and saving it to an SD card, also displaying the temperature on LCD TFT Screen.

If I don't connect the sensors, it works perfectly for hours.

but when I connect the sensors, it will work fine for around 15 minutes and then the screen blackout.

the Arduino keeps saving the information on the sd card and displays them on the serial monitor but no LCD.

The Screen will not function again unless I turn the power off for 3-5 minutes (simple off/on will not work).

the power consumption during normal operations (screen and sensors 0.2 Amp) but when the screen is off the power jumps to 0.6 amp. power supply is 5V, 2 amp.

​

I tried to power the sensors from Arduino or from an external power supply, same problem.

The DS18b20 code using OneWire and all of them are connected with the below picture.

​

forgot to mention 680 ohms between power and data, it is not 4.7kohm because of the cables length (cable resistance)

Hardware with simple power

+ LCD TFT 3.5 inch screen Screen LINK

+ Arduino RTC module ds1302

+ 14 temperature sensor DS18B20

if you need the code is ok but it is too long

[Railroader]

You really need to provide schematics.
More: Read this link and proceed according to it: How to get the best out of this forum - Using Arduino / Project Guidance - Arduino Forum

@ammaralroz

if you need the code

Try to run the project without any code.......

[Wawa]

@ammaralroz

680 ohms between power and data, it is not 4.7kohm because of the cables length (cable resistance)

Max sink current of a DS18B20 is 4mA, which works out to a minimum resistor value of 1k2.

@ammaralroz

If I don't connect the sensors, it works perfectly for hours.

Are any of them getting hot.
Leo..

[bluejets]

@ammaralroz

forgot to mention 680 ohms between power and data, it is not 4.7kohm because of the cables length (cable resistance)

Nope....
BTW...how many kilometers is your cable..???

[Wawa]

@ammaralroz

power supply is 5V, 2 amp.

How/wher did you connect it to the Mega.
Leo..

[ammaralroz]

@Wawa

Max sink current of a DS18B20 is 4mA, which works out to a minimum resistor value of 1k2

I will try the 1k2 resister today.

@Wawa

Are any of them getting hot.
Leo..

If you mean the sensors, they are connected to a car with maximum reading of 70c.

The arduino and screen environment around 40c

[ammaralroz]

@bluejets

Nope....
BTW...how many kilometers is your cable..???

Each cable between 3 to 15 meter. 3 core cable (similar to cat5).

When I connected 4.7kohm only 3 sensors worked. The more resistance I reduce the more sensors I can add.

[ammaralroz]

@Wawa

How/wher did you connect it to the Mega.
Leo..

Car charger. The project inside a car.
Tried also 12v to 8v to VIN. dame problem

[Wawa]

Where did you connect the 5volt/2Amp supply to.

1. USB
2. DC socket
3. V-in
4. 5volt pin

You said that current draw is 400mA more when the screen blanks after 15 minutes.
That's 2watt.
Something has to get hot from that.

@ammaralroz

Each cable between 3 to 15 meter.

Did you wire the sensors in a star configuration.
Would you have used less wiring when used inline.

Plenty of pins on a Mega.
You could use one pin for each sensor. Or have several groups of two or three sensors.
Leo..

[ammaralroz]

Appreciate your help

@Wawa

Where did you connect the 5volt/2Amp supply to.

5v pin
(Tried also usb from computer and vin 8v (different power supply) same problem

@Wawa

Plenty of pins on a Mega.

True. But I have small space. I can try 2 pins as start.

@Wawa

Did you wire the sensors in a star configuration.
Would you have used less wiring when used inline.

Unfortunately all wires coming to same place. So I installed this using this

[ammaralroz]

I changed the tempreture sensor DS18B20 resistor to 960ohm. More then that it doesn't read anything.

When I connected everything for an hour. It worked fine. But when I start the car engine. And tempreture start to be around 45-50. The screen disconnected and the screen back IC got very hot.
I put the screen opposite of the AC. and it is still working fine.

Not sure it is normal or faulty screen or it need heat sink?

[ammaralroz]

I have changed the screen and added heatsink. Same problem.
Working fine without starting the car. After starting for about 10 minutes the screen blackout.
PLEASE HELP

The code
final_display_With_SDCard_600_v5.ino (21.9 KB)

[bluejets]

@ammaralroz

When I connected 4.7kohm only 3 sensors worked. The more resistance I reduce the more sensors I can add.

No....you still need the 4k7......... if you add more sensors and each has the pullup, you will be dividing the resistance down...not good
3 to 15 metres of cat5 does not add up to your calculated resistance......

Think you need to get back to basics.......

How about this..?? ...just show what you have in code and in a circuit diagram that includes everything like power supply etc.

Car battery chargers (if that is what you used) are not power supplies per se...........there output is rarely smooth dc.

Beats me why you need so many sensors anyhow.

[cedarlakeinstruments]

@bluejets

Car battery chargers (if that is what you used) are not power supplies per se

I was wondering if this might be the problem. The USB car chargers that I've taken apart seem fine though: good clean output.

@OP: have you measured the 5V signal at the display when the car is running? Also, are all the grounds going to the same place?

Clearly your display is overheating. The only reasons it should are either because its power supply is above 5V, or possibly that the 5V is drooping and the control signals from the arduino are greater than the display power supply, causing a "reverse power" situation.

It's critical to take measurements while the engine is running since vibration can affect connections that are fine when it's not running.