This I2C project is going to be the end of me.

Projects Networking, Protocols, and Devices
1

Beginner Amateur Electrical Engineer/ Professional Expert Software Engineer

This project is going to be the end of me. I am admittedly very new to soldering.

I am trying to create an Arduino Weather Station.
Right now I am trying to use perf board to create an I2C bus to connect the following:

Adafruit BMP180 - BMP180 Barometric Pressure/Temperature/Altitude Sensor- 5V ready : ID 1603 : $9.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Adafruit TSL2561 - Adafruit TSL2561 Digital Luminosity/Lux/Light Sensor Breakout : ID 439 : $5.95 : Adafruit Industries, Unique & fun DIY electronics and kits
MOD-1016 Lightning Sensor - Embedded Adventures - Products - MOD-1016 AS3935 Lightning and Storm Sensor Module

I just want to connect the 3 of these devices to I2C.

Last night, I spent a number of hours soldering a bunch of female headers on a board.
First I connected the BMP180, then ran I2C scanner: detected success!
Then the lux sensor: both devices now detected.
Then the lightning sensor: all 3 devices connected.

I am using all-purpose flux from Lowes, so I decided to clean the board with 70% rubbing alcohol, and let it dry and test again in 24 hours.

Fast forward to today. Nothing detects.
All the devices work fine when individually connected, but when connected to the PCB nothing works.

So I decided that the rubbing alcohol was a bad idea, must have left some residue, and set out to create a new PCB.

Went through the entire process again. All 3 devices detected. Cool.

Then I decided to try to get readings from the device. Fired up the BMP180 library. And it pulled a value.

Fired up the lux sensor library, and it was very sluggish to detect....and pulled a single value.

I then decided to run the i2cscanner again. And nothing will detect.
It's as if my circuit only worked for 5 minutes, and then broke down.

Individual Sensors still work, but the PCB no longer works.

This is the 3rd time making a PCB for this, and I can't get it to work.

I attached a photo of the PCB. I know it looks like a disaster, but I swear it worked for 5 minutes.
Using 60/40 leaded solder.

It's driving me nuts.

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2

Added a photo of the other side. I know it's not sexy, but I expected it to at least by functional for more than 30 seconds.
It's as if the solder joints break down after 5 minutes of 5 volts, how likely is that? Is it my solder, my technique, my flux?

I tests continuity across all of the circuits, and they all checked out. No shorts from what I can tell.

Could the flux I'm using become conductive as it ages and shorting a couple neighboring pins? Could my arduino be cursed with a demon that is trying to break my spirit?

My Solder: Kester Solder Products 14-6040-0062 Kester Solder Products Solder | DX Engineering
My Flux: https://www.lowes.com/pd/Worthington-2-fl-oz-Petroleum-Soldering-Flux/3829729

Oh crap, it's the flux, isn't it?

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3

I am using all-purpose flux from Lowes,

I don't know what this is, but would recommend that you go to Radio Shack or some other electronics stores and buy some good quality PCB multicore solder. No need for external flux.

If the "all purpose flux" is acidic, it will destroy your board in very short order.

Check out on-line soldering tutorials from Adafruit and Sparkfun.

4

jremington:
I don't know what this is, but would recommend that you go to Radio Shack or some other electronics stores and buy some good quality PCB multicore solder. No need for external flux.

If the "all purpose flux" is acidic, it will destroy your board in very short order.

Check out on-line soldering tutorials from Adafruit and Sparkfun.

Yup, and I think it might be conductive as well. Rookie mistake I guess.
Every radio shack around me closed like last month, Sad. I guess I'll have to wait for amazon.

On the plus side, I've gotten better at soldering with practice. So when I get the right materials I should be able to whip up a new PCB in short order. Any way to clean the one I have?

5

It is probably not worth the effort to clean the one you have, and may not even be possible.

You will also need a fine tip soldering pencil, 30-40W (if you can afford it, temperature controlled). Good tools make a huge difference in your success rate!

6

Get some high concentrate isopropyl alchohol and a stiff brush. Your local drugstore may carry it.
I use 99.9% anhydrous isopropyl, bought a gallon bottle at my somewhat local electronic supply center near Boston, MA.
CVS has I think 70%, maybe a little higher, very wet stuff (30% water), takes a while to dry. 99.9% evaporates very quickly.

7

It was the solder/flux.
With some proper rosin core solder. I was able to make everything work.
Thanks for the info everybody.