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Goofed BT Temp, Light, Humidity sensor...

MSP430G2553 DHT11 LDR bluetooth

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#1 0xFFFF

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Posted 19 January 2016 - 08:22 AM

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.

 

 

TIA

 

0xFFFF

Attached Thumbnails

  • Weather thingie_Page_1.png
  • Weather thingie_Page_2.png
  • DSC_3660.jpg

Attached Files

  • Attached File  main.c   6.77KB   58 downloads


#2 yosh

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Posted 19 January 2016 - 10:58 AM

Hi

 

maybe you can go a little bit more into detail what is working or not (on your PCB). Does the MSP power up, is the code running (= LED blinking every second). Does the BT module (which one? guessing HC05/06 from the pinout) power up (blinking, can you connect)?

 

Kind regards


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#3 0xFFFF

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Posted 19 January 2016 - 12:31 PM

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.

 

TIA



#4 yosh

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Posted 19 January 2016 - 01:00 PM

 

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=10µF ? According to the datasheet 1µF should be ok ?



#5 Frida

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Posted 19 January 2016 - 06:39 PM

What with pull up resistor to DHT11, and open collector output from mc?

 

See

 

http://www.robotshop...s/pdf/dht11.pdf



#6 Frida

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Posted 19 January 2016 - 06:40 PM

What with pull up resistor to DHT11, and open collector output from mc?

 

See page 5

 

http://www.robotshop...s/pdf/dht11.pdf


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#7 cde

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Posted 19 January 2016 - 07:33 PM

High res picture of your PCB, Both sides.



#8 0xFFFF

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Posted 19 January 2016 - 10:01 PM

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=10µF ? According to the datasheet 1µF should be ok ?

 

I'm aware that the pull up should be 4k7 47k (typo).

The external supply is ~5VDC 200mA to the 3V3 regulator. The MSP430 is attached to the 3V3 rail (I've tested the output of the regulator)

 

I didn't do this with all of the components but I should have. I'll investigate this further tonight when I get home.

C1 is unnecessary. It's a copy paste from another schematic that had a requirement for it. Shouldn't do any harm being there.

 

 

What with pull up resistor to DHT11, and open collector output from mc?

 

See page 5

 

http://www.robotshop...s/pdf/dht11.pdf

 

Ohhh. I forgot about that. I'll bodge that in tonight. Thanks for spotting that Frida!  :)

 

High res picture of your PCB, Both sides.

 

I've updated the original post with the PCB output. I can post an actual photo of the PCB tonight.



#9 yosh

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Posted 19 January 2016 - 10:15 PM

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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#10 0xFFFF

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Posted 19 January 2016 - 10:29 PM

47k ... not 4k7 ;-)

 

Ah. Thanks yosh. It's a typo. The schematic is correct.



#11 0xFFFF

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Posted 19 January 2016 - 10:36 PM

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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#12 0xFFFF

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Posted 20 January 2016 - 10:55 AM

I attached a photo of the PCBs to the first post.

 

Wasn't enough time to get much done tonight. :(







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