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Goofed BT Temp, Light, Humidity sensor...

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Hi All,


Somehow I've made a stupid mistake with this weather thingie I put together and I can't figure out what's wrong. I need your help!


Project description: Weather thingie - Reports temperature, humidity and light readings via bluetooth.

Operation is simple, connect to the device and it will report something like "27 C 57 H 96 L\r\n" ~ every second. The LED on board will alternate state every second.


I set this up on a breadboard before making the PCB as I was not familiar with the DHT11 or and quirky requirements it might have. The project worked fine on the breadboard.

I suspect I have either a PCB design fault or defective components? Perhaps? I dunno.










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Thanks yosh.

Suppose I should help you help me eh? (oops :blush:)


I have two boards (now). Same results for both...

They power up and everything appears to function as it should BUT the MSP430 is overheating to the point where it malfunctions.

As the MSP430 heats up the regulator on board will follow shortly after due to an increase in current draw. I shutdown power to the board before any permanent damage can be done.


I forgot to mention that I changed the 4K7 pull-up on the reset to 0R as the MSP wasn't starting. Which I think is a bit suspicious.


The BT module is a BK3231 (similar to a HCxx). I can connect to it, there is nothing wrong with the BT module as far as I can tell.

I have HC modules, I'll assemble another PCB and see if there is a difference there.

I assembled another board using a HC05/06 BT module. It exhibits the same behavior as the other board but I can't connect to it. I didn't bother checking its configuration. I'll do that later after I get some sleep.


I have tried removing the regulator and running directly from a lab supply but the MSP430 will still heat up.

I have not tried running without the BK3231

I have not tried running without a BT module.



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I forgot to mention that I changed the 4K7 pull-up on the reset to 0R as the MSP wasn't starting. Which I think is a bit suspicious.



The resistor for reset should/must be 47k (47.000 ohm)!

Do you power the circuit with 3V3 as in your scheme?


Did you try to solder the board step by step and check each part, e.g. first LDO, then MSP430, ... ?

Why C1=10

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47k ... not 4k7 ;-)


Out of curiosity - where were the PCBs manufactured and what is the trace width and minimum clearance. Looking at the picture you added some traces look very close to each other or close to pads/holes. Can you check if there could be a short somewhere ? For me the layout looks very tight at some places ... but maybe it is all OK and I am definitely not as expirienced as others here.

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PCB manufacturer is the very capable, fast and friendly team at Fusion PCB. I'll post a picture of the PCB tonight for your reference.

Everything is within tolerances. I wanted to keep this design single-sided (I have no reason).


I've designed plenty of boards in the past that have pushed beyond the tolerances of this particular PCB. 

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