Uno Power Supply Issue

HI guys, I have been working on a little continuity tester project recently. Basically, I am pulling 4 digital

pins HIGH (5V) and lighting the LED to confirm the continuity of the wire:

Digital pin (5V)--------wire under test---------R220ohm---GREEN LED----GND

The same setup is replicated for 4 wires individually.

I am using 9V(dc), 3A rated power supply to power the board and light 4 LED's.

For some reason, UNO board is getting very hot and has stopped working now. Can anyone please help

me figure out where the problem is.

int pushbutton = 8;
int pushstate;
int line1 = 0;
int line2 = 1;
int line3 = 2;
int line4 = 3;


void setup() {

pinMode(pushbutton, INPUT);
pinMode(line1, OUTPUT);
pinMode(line2, OUTPUT);
pinMode(line3, OUTPUT);
pinMode(line4, OUTPUT);


}

void loop() {
pushstate = digitalRead(pushbutton);

if(pushstate == HIGH){

digitalWrite(line1, HIGH);
delay(500);
digitalWrite(line2, HIGH);
delay(500);
digitalWrite(line3, HIGH);
delay(500);
digitalWrite(line4, HIGH);
delay(500);

digitalWrite(line1, LOW);
digitalWrite(line2, LOW);
digitalWrite(line3, LOW);
digitalWrite(line4, LOW);
delay(300); 

}
else
delay(1);
}

Some short circuit. Disconnect everything from the board and try if it works.

Switch is connected as shown in the link above (10k pull down resistor)

I have stripped down the whole thing down, can't see any short circuits. The board is powering up but it

won't program.

I have attached the schematics, please have a look.

Schema

technophile:
...
I have stripped down the whole thing down, can't see any short circuits. The board is powering up but it
won't program.

Is the UNO still getting hot?
If you have DMM you can check the voltage on some points: Vin, +5V, etc. Carefully!

Does it work when powered through USB?

Does the simple blink sketch work?

Note that using pin 0 as an output will prevent you from using the serial monitor ... I think it may also cause cause programming problems (specifically the resistor and LED load). I would refrain from using both pins 0 and 1.

Which part is getting hot?
Is it the 5V regulator next to the barrel jack connector? That's replacable with a soldering iron. Do you measure 5V and 3.3V at the power header?

Is it the 328P chip itself? If so, the chip is fried, get a new one from www.dipmicro.com or www.adafruit.com

Is it the USB/Serial chip, the small surface mount chip near the USB connector? You're out of luck replacing that without hot air rework station. Does the Loopback Test work? (In the Installation & Troubleshooting forum)

Hi Guys, thanks for the feedback. The board is getting hot even when powered by USB. I've noticed that

its the microcontroller itself getting hot. output of the 5V regulator is 4.3V. Power LED turns on, reset

button is working too. However, board won't program anymore.

Which type of UNO? If it is chip in socket, it is easy to replace the chip. You can buy new one with the bootloader - just replace.

EDIT: But wait, 4.3V is little bit low. Maybe, just MCU is drawing high current. Remove the chip if it is possible and check the regulator again.

Are you sure that the wires in the cable are not shorted together and sending current back from a HIGH output into a LOW one? I would tie all wires on one end of the cable to ground, then connect the output pins, resistors, LEDs to each wire on the other end.
Or better maybe, keep what you have and make the 3 unused output pins inputs while testing with the one output, that will keep fault current from flowing backward through a LOW output pin.

int pushbutton = 8;
int pushstate;
int line1 = 0;
int line2 = 1;
int line3 = 2;
int line4 = 3;


void setup() {

pinMode(pushbutton, INPUT);
//pinMode(line1, OUTPUT);
//pinMode(line2, OUTPUT);
//pinMode(line3, OUTPUT);
//pinMode(line4, OUTPUT);


}

void loop() {
pushstate = digitalRead(pushbutton);

if(pushstate == HIGH){
pinMode(line1,OUTPUT);
digitalWrite(line1, HIGH);
delay(500);
pinMode(line1,INPUT);
pinMode(line2,OUTPUT)
digitalWrite(line2, HIGH);
delay(500);
pinMode(line2,INPUT);
pinMode(line3,OUTPUT)
digitalWrite(line3, HIGH);
delay(500);
pinMode(line3,INPUT);
pinMode(line4,OUTPUT)
digitalWrite(line4, HIGH);
delay(500);
pinMode(line4,INPUT);

//digitalWrite(line1, LOW);
//digitalWrite(line2, LOW);
//digitalWrite(line3, LOW);
//digitalWrite(line4, LOW);
delay(300);

}
else
delay(1);
}

If the chip is hot, it's blown. What typically kills them is one or more IO pins were subjected to a high voltage, or allowed to sink/source too much current. I suspect the VCC/Gnd clamp diodes fail or the output transistors fail and short VCC to Gnd internally causing the high heat.

What leds are you using?? How many mA do they pull each?

technophile:
For some reason, UNO board is getting very hot and has stopped working now. Can anyone please help
me figure out where the problem is.

Was the board doing what you wanted it to do prior to the board failing due to heating up?

I am using green LED's. According to datasheet, each LED pulls 10mA current.

I'm building a continuity tester for cables containing 4 wires each and 4 LED's represent if there is good

continuity across each wire.