Arduino pro mini gets so HOT

Projects General Guidance
1

Hello everyone.
I bought two Arduino pro mini 3.3V and I was trying to make a radio transmitter and receiver like this.

I couldn't get it work, by the way I realized that the Arduino in the transmitter was getting too hot

I was supplying both with a 9V battery through RAW pin

Even when i connected it through VCC with a 3.3V regulated supply, it still got so hot

I desoldered the regulator and supply it with 3.3V through VCC but it still gets hot

The exact part with gets hot seems to be the programming pins, like RX or VCC

So I meassured the resistance of several pins and here is some of them which are different than the other Arduino which doesn't have any problems:

pin1----pin2:::::damaged Arduino ------- healthy Arduino

VCC-------GND:::::::::::0 ohm!!----------------2 kilo ohms

Well I just realized that VCC and GND are shorted, there isn't any problems with soldering and it was working fine before, what has happened to it? is it fixable at all?! what can cause and Arduino short VCC and GND?!

2

Let me mention that I guess the board works and run the code that I had uploaded before
But as it gets hot so fast, I have to unplug it after maximum 6, 7 seconds or it will burn itself

3

Show us a good image of your ‘actual’ wiring.
Posting images: Simple guide for inserting images in a post - Website and Forum - Arduino Forum

4

I'm guessing you are trying to run the NRF24 units directly from the Arduino 3v3 supply which won't work.
The author uses a 1A regulator in his project to overcome this requirement.

Not enough power handling ability from the onboard regulator on the Arduino module.

Use the NRF24 adaptors and power them from a 5V regulated supply.

Common to use a 7.4v Lipo and a small buck converter to drop down to the 5V required.

Adaptor.jpg
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BuckConv.jpg
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Adaptor.jpg
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BuckConv.jpg
BuckConv.jpg1117×1117 99.6 KB

5

larryd:
Show us a good image of your ‘actual’ wiring.
Posting images: Simple guide for inserting images in a post - Website and Forum - Arduino Forum

bluejets:
I'm guessing you are trying to run the NRF24 units directly from the Arduino 3v3 supply which won't work.
The author uses a 1A regulator in his project to overcome this requirement.

Not enough power handling ability from the onboard regulator on the Arduino module.

Use the NRF24 adaptors and power them from a 5V regulated supply.

Common to use a 7.4v Lipo and a small buck converter to drop down to the 5V required.

As you see in the second pic, I connected 9V battery to servo (bad job), so I disconnected the servo and changed the code of "receiver" so instead of trying to control the servo, I was trying to monitor the value using serial monitor (like this page). but I was not successful.

Each Arduino would start blinking after sometime and I didn't know what the cause was. I just know the couldn't run the uploaded codes. After disconnecting them from power supply and connecting again, that might became working again or still blinking.

Then I saw the receiver doesn't work anymore and always blinks (50 ms ON, 1 second OFF). So I decided to burn bootloader with the Arduino on the transmitter side.

I disconnected all the wiring.

I successfully uploaded Arduino ISP to transmitter.

Connected both Arduino together as I successfully did it before (like here)

I clicked "burn bootloader".

Then I got an error which said it failed to burn bootloader.

At that time I saw that the transmitter Arduino is extremely hot.

So Actually the receiver Arduino is not completely fine neither, but I believe I can fix it if I burn boot-loader to it using my ESP8266 WeMOS D1 WiFi.

6

After desoldering the regulator, I decided to desolder the capacitor next to it.
After that I connected 3.3V to VCC and it didn't get hot for two minutes, then started to get a bit hot.
After uploading different codes like "blink" and "Arduino ISP" and "servo", I see it hasn't got hot or even warm yet. I can't figure out what exactly happened! I hope it doesn't get hot anymore.
By the way I have some problems now with Arduino pro mini on the receiver side -_- and I'll post it in a different topic.

7

Hi,
Do you have a DMM to measure your circuit paramters.
If you remove the Nano and NRF and power the board, do you have voltages at the appropriate points?

Tom... :slight_smile:

8

TomGeorge:
Hi,
Do you have a DMM to measure your circuit paramters.
If you remove the Nano and NRF and power the board, do you have voltages at the appropriate points?

Tom... :slight_smile:

Yes I have. Now that I have removed the regulator and capacitor, every measurement is okay.

But in my previous post when I said:

erfan_m14:
pin1----pin2:::::damaged Arduino ------- healthy Arduino

VCC-------GND:::::::::::0 ohm!!----------------2 kilo ohms

It was when nothing was connected to the board even a power supply, and when I would only connect VCC and GND, there was still 0ohm resistance! so it was the cause of getting so hot.

But after removing capacitor it was fine for 2 mins, then again it became hot and there was again 0 ohm resistance, after I uploaded several random sketches, it became okay and hasn't got hot or warm yet.

9

Hi,
When you up load do you have the 9V supply connected?

If so even though the Nano "should" have protection circuitry or on board 5V regualtor, having the battery connected during upload may be causing some of your problems.

Do you have your project constructed on Vero, stripboard, protoboard, or a PCB?

Thanks.. Tom.. :slight_smile:

10

TomGeorge:
Hi,
When you up load do you have the 9V supply connected?

If so even though the Nano "should" have protection circuitry or on board 5V regualtor, having the battery connected during upload may be causing some of your problems.

Do you have your project constructed on Vero, stripboard, protoboard, or a PCB?

Thanks.. Tom.. :slight_smile:

I don't remember last night when I was uploading a code, 9V was connected or not but I don't think so.

Yet I'm using a breadboard but I will be have it on a PCB when I'm sure it works.

11

erfan_m14:
As you see in the second pic,

No, not really.
Both diagram are not legible.

12

bluejets:
No, not really.
Both diagram are not legible.

Right click on the image and click on "open image in new tab", and then zoom.

13

after 3 hours, again I powered it on and it got soo hot immediately and again no resistance between VCC and GND. I really can't guess what is going on :smiley:

14

Hi,
Can you post a picture of your project so we can see your component layout?

What are you using for your 9V supply?

Thanks.. Tom... :slight_smile:

15

TomGeorge:
Hi,
Can you post a picture of your project so we can see your component layout?

What are you using for your 9V supply?

Thanks.. Tom... :slight_smile:

From the time that I desildered the regulator, I haven't used it in any circuits, just tried controlling a servo motor and it was okay, and I powered the servo with external battery not Arduino. And it worked great, just after 2 hours, I connected TX RX VCC and GND to the USB to serial converter and connected it to my PC and it became hot

The converter doesn't have any problems because I use it with my other pro mini without getting hot

I think I should give up on the board and buy another one! -_-

16

erfan_m14:
After desoldering the regulator, I decided to desolder the capacitor next to it.
After that I connected 3.3V to VCC and it didn't get hot for two minutes, then started to get a bit hot.

Some (tantalum) capacitors can burn boards when overloaded or by wrong polarity. You may have got a series of boards with too weak capacitors, or with capacitors soldered in reverse. Check the removed capacitor whether it gets hot when connected to a power supply of the correct voltage.