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Can Fez power up a 3.3v bluetooth module + 5v 16x2 LCD?


Hi, I’m just cautious because I’ve read in the past that some Fez died from ??overheating that resulted from too much load?? - not sure

As of now, I’m powering the Fez using the USB connection. It can power up the 3.3v bluetooth module, and still keeps itself normally warm.

But when I remove the 3.3v(removed from the 3.3v pin) and replace it with a 5v 16x2 LCD(placed in the 5v pin), the Fez starts to get hot, maybe 45C++? in just 10sec of using (just tested a display on the LCD,then immediately disconnect). Is this normal?

Can a 9v adapter safely power up the FEZ with a 3.3v BT module + a 5v 16x2 LCD? or should I use a different power source to power up the BT module and the LCD and not use Domino’s 3.3v and 5v pins?


If you can keep your finger on the regulator for 10 seconds then it is not too hot


I was touching the USBizi chip. :smiley:

So Fez should easily/safely power up the BT module,the LCD, and a flash drive using a 9v adapter?


You’ll probably need to figure out how much current all your devices are consuming and at what voltage they’re operating at, to really make sure you’re not doing something that’s going to kill your board’s regulators quickly.

You need to figure out how much current each of the 5v and 3v3 regulators will be called on to convert, from 9v. Remember that it’s a smaller drop (less temperature gain in your regulators) if you only are regulating 7v down to 5v instead of 9v, so if you have options, go with a power pack of 7v.


Depending on how much current your devices are drawing.

USBizi chip should NOT get any warm but note that if the board is warm then the chip will be warm and this is normal. Like I said, if you can touch the regulator for 10 seconds then ti is not too hot. If you finger hurts then you need to lower the voltage.

Linear regulators lower the voltage by converting it to heat so heat is normal to an extend.


I’m not good in electronics, how do I find the regulator?

I’ve touched a 3pin ?chip? beside the external power connector with a label “IC3” on the board, and I could only touch for a second as it was to hot.

I looked on the tech sheet of my BT module and found this:
Supply Voltage: 3.0 - 3.3 Volts
Input/Output Ports (I/O): 10
Internal Input Pull-up/down Current: 40uA
I/O Input Voltage +0.8V (low): / 0.7*VDD (high)
I/O Output Voltage 0.2V (low): / VDD-0.2 (high)
I/O Source/Sink Current: 4mA

While the 16x2 LCD datasheet from sparkfun says it uses 60mA with backlight fully on.


It is the part that gets hot on the board.

No need to see specification of anything. If you touch anywhere on the board and couldn’t keep touching it for 10 seconds then you need to lower the voltage.

Note that if you are using a non regulated power pack then your 9V power pack is probably outputting 12V.

I personally use power packs with different output voltage so I can select what voltage I want.