Let's Make Robots!

How to make a ADXL345 for a $1.00

I2C Accelerometer

1. Get over to Analog Devices and sign-up for a sample account. They seem to be pretty nice and let you order several samples every month, I believe.

2. Order a few samples of the ADXL345 chip from Analog Devices.











3. Download the Eagle files from Sparkfun:  ADXL345 (Note the price).











4. Sign up for an OSHPark account.  Then, upload the .brd found in the Eagle files.














5. Order the capacitors.

2 x 0.1uF

1 x 10uF 

6.  Try to learn Python while the mail peoples do their magics.
















7. Flip-off your Python code and get the mail.  

8. Take everything out.  ADXL breakout board, ADXL345 chip, and caps.

9. Populate your board.  At this point, a good iron will do you well.  But as a general rule, start with the largest chip when soldering SMDs.  In our case, it is the ADXL345.  Paint some solder flux all over the exposed pads.  Now, take a very fine solder, such as .022 and put some on the tip of your iron.  Drag the droplet of solder across the exposed pads of where the ADXL will go.  Now, after the beads have cooled, paint your solder flux over the hardened beads.  The idea is to have the chip floating on this flux.

10. Place the ADXL345 on the invisible flux, hovering over the pads.  Make sure the small white dot on the the corner of the chip is in the same place the red is below.

11. Put the board on an over turned iron.  This is the most important part: Watch the chip.  What you are hoping to see is the chip magically float in place as the solder flux flows out from under the chip, leading to the solder beads bonding with the exposed copper of the ADXL345.  Seriously, don't look away :).  If for some reason you don't feel the chip has bonded at each pad, then very lightly press down in the middle of the chip.  I said lightly!

12. Cap that B.  Erm, populate the capacitors.

13. Plug and pray.

14. Realize it doesn't work because you suck at life.

15. Pull the ADXL back off, clean the pads with solder wick, and try again.

16. Repeat step 11, but this time, watch the chip, no seriously.

17. Hook it up and check it out.  The chip is both SPI/I2C ready, but I prefer I2C.  So, hook that sucker up to the Arduino and see if it works.  This fellow provided code and instructions on connecting are in the code's comments at the top.

Arduino Code for ADXL345 I2C

18. Watch as your one dollar(ish) ADXL345 does witchery.

19. Ponder the ethics of sampling chips, borrowing board layouts from SparkFun, and buying underpriced capacitors from China; all leading to saving you around $12~25--or have a beer.

20. Try not to abuse the sampling previlige.

If you have any questions, I'll do my ignorant best.

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Just wanted to tell that I managed to solder this chip on a piece of pcb.

I ordered this one:


That's even cheaper then making the pcb through osh park. And the caps are bigger on this one.

Thank you :)

Did it all go together ok? If so, I'll order a few of those boards.

The board works just fine. Only the holes for the breadboard pins are way too small. I had to use pliers to get them in. Beware that the caps are bigger so you'll probably need different ones than you had now.

Also I soldered the caps together with the big chip. Saves the soldering iron hassle.

Very humorous, informative and concise, all at once :D Way to go Lad!

Alas I wouldn't dare go SMD while I still pretty much still suck at regular through the hole soldering :| Also Mr. Ebay from the East sells these modules starting at little over 2 bucks, and maybe less if you're willing to enter bid wars :P

Regardless, very nice... I should task you with composing my next walkthrough :P Congrats :)


As for handling pythons and their like I rather muter to myself and curse angrily when they're not complying :P

This one is $4.00--and the Vcc looks regulated. But...mine...has a great personality? http://item.mobileweb.ebay.com/viewitem?itemId=310619508850&cmd=VIDESC And in all fairness, the boards were $2.00 for three. So, Mr. EBay is the better deal. But I learned a lot :)

Your post just fed my ebay beast... and I went on a bid war, and snipped one for $2.65 :P

But yeah, I'm all for learning, I also do a lot of things from nearly scratch in order to learn more about things :) However, like Max... SMD soldering still "scares" me.... so it is not something I'm eager to jump into right now :P let me master first through-the-hole soldering, and we'll see ;)

Nice humor to your post.  I do like python, accelerometers, and .... beer.  Reminds me of some boards I made from OSHpark although the accelerometers cost $3 and I laid the board out.  I will try your technique out for soldering as it will be faster than what I've done: flux/solder both the board footprint and the IC pads, then toaster oven.

It's QFN with bottom pins, no leads.  Going to try the iron method, but I'm not hopeful.

Of course, I still have to dig through the datasheet and design a circuit.


I suppose doing what worked for you before may work here.  You may want to use an eye loop or microscope to make sure things are looking good before you plop down a $15-$20 IC.  It may help to do as I mentioned which is tinning both the IC and board with solder.

Are you planning a 2 or 4 layer board for this?  I haven't gotten around to designing a 4 layer board yet, not sure if there is a free version of a good PCB design suite that enables more than two layers.  Of course there is always gEDA or KiCAD.

Congratulations-you've managed to include pictures and suggestions concerning the two things I fear most in one post-SMD soldering projects and snakes ;-) nice work though!