XBee getting so hot it could burn me

I’ve got an Arduino Fio project going on. It’s a controlpoint button system to make airsoft games more spicy. :slight_smile:

I built a custom PCB which the Arduino connects to. It’s my first custom PCB ever.


I connected everything together to try it out. It seemed to work at first, then I started noticing random sketch crashes. The crashes are very noticeable because the start of my sketch makes a buzzer beep, and a neopixel strip lights up a test pattern.

Anyway, I thought it was just my poorly written code causing the occasional crashes, so I let the Arduino Fio with XBee run some more. It kept happening more and more so I pulled open the project box to take a look. As I picked up the PCB, I felt heat coming from the XBee (S2B 900 series). WOW was it hot. If I kept my finger on the XBee, it definitely would have burned my skin. I quickly removed the project from power and now I’m taking this issue to the forum. Anyone ever seen or heard of something like this?

Here’s a video of the heat problem reproduced. The project had been powered off for days, and the XBee heated up to unsafe levels within seconds.

My first thought was that the XBee was powered incorrectly, or shorted out? But this thought doesn’t make much sense since the XBee isn’t wired to the arduino in the traditional sense. Other than plugging it in backwards, I couldn’t have got it wrong. It’s connected straight to the Arduino Fio through the Fio’s XBee socket.

My Second thought is inappropriate power to the Arduino. Reverse polarity maybe? A short somewhere? This thought doesn’t make much sense because the sketch ran successfully, and I was receiving valid packets on the other end over the air.

My third thought is a bad XBee. Maybe an internal short. This one I can test just by switching out for another XBee, which I haven’t done yet. I’m just thinking aloud here. It helps to have someone to talk to about this sort of thing.

My fourth thought is the antenna. It’s a 2.4GHz antenna even though the XBee is 900MHz. I didn’t have any 900MHz antennas on hand, I don’t know how much that matters.

My fifth thought is the PCB. Actually this is more like the first thought, but I can’t remember if the crashing problem existed pre-PCB or not. I’ll have to hook up my testing breadboard again to check this one.

Thought six is the batteries. They are reclaimed from old laptops. Maybe they are damaged and there is some weired internal resistances that are heating up the wires?? IDK, there be ghosts here, power circuits are not my specialty!

I’ll go through each potential problem I noted, eliminating as many as possible. If anything seems obvious, please let me know. I’ll update as I make discoveries. Thanks!

PCB


Code

d3vice-controlpoint-xbee.ino

Anyone ever seen or heard of something like this?

Sure, it happens when you get the power supply connections wrong on a PCB design for instance.

Its good practice to connect a 'new' design up for the first time with a current limited power supply, this way you can identify problems before they get a chance to fry something.

Unplug the XBee.

Measure the current comming out of the battery, how much is it, is the current level normal ?

Plug in the XBee.

Measure the current comming out of the battery, how much is it now ?

How is this a Networking issue?

srnet: Sure, it happens when you get the power supply connections wrong on a PCB design for instance.

LOL :)

Thanks srnet, I will try measuring current. I just discovered my Fluke 101 can't do that, so I will have to borrow a different multimeter from a friend.

PaulS: How is this a Networking issue?

Networking device issue wink.