Archive for the ‘Soldering and DIY Fabrication’ Category

Probotix X90 CNC – Cutting Servo Mounts in Sintra PVC Foam Board



This is the first cut of my Probotix X90 CNC. Absolutely amazing!

I am using the EMC2 Linux CNC installed on an old computer installed using their Live/Bootable CD.

The model was created in Sketchup 2013 then exported to STL using this plugin :

Then I used MeshCAM 5 to convert the STL to GCODE file.

As a cutter I used a 1/16 4 flute carbide bit normally used for PCBs – the only one that I had available, but specialized 2 flute cutters should work better – I might try that. You’ll see this bit creates a lot of burring so parts needed cleanup.

The bit is mounted in my trusty Dewalt DWP611 router :

I am using a 1/4 to 1/8 collect adapter since the DWP611 comes with only 1/4 adapter.

It gives me good run-off of max 2-5mil which is ok for my application.

However ultra-precise collets can be found here:!!!Dewalt_611!!!Kit!!!PG!!!

They claim a runout of ~  0.4 mil

Here is the final result, I simply glued 2 parts together to make them thicker. You’ll see that this is a servo mount for 9g Hitec servo on 13x13mm aluminum tubing that I got from HobbyKing



Hope this helps. Happy CNC-ing !


Use extra-long headers to hold a board on a pogo pins testing jig

Adafruit has a nice tutorial on how to build a neat testing jig that allows you to test a breakout board without having to actually solder the header.

So I decided to build one for  the the acc_gyro boards. But how do you hold the board in place ? Using screws is secure but takes long time to put a board in and out. I needed a faster way to test a larger amount of boards.

Well after several experimentations with velcro tape, rubber bands , and even custom fitted clamps made out of polymorth , I arrived at this simple solution, just use some headers with extra long leads , the pictures tell it all:

The board is basically held by the plastic parts of 2 long headers. You simply spread them apart, insert the board and then , when they come back together they hold the board in place by the spring action of the pogo pins that pushes the board up.

To remove the board simply spread the headers again and the board pops up …

Hope the method could be useful to someone , so decided to share.


DIY Surface Mount on a Budget – Complete Walkthrough from PCB etching to Reflow


Sometimes you need to use a device and it's only available in surface mount form. In this article I describe an experiment that I conducted in order to create a DIP adapter for an LGA-14 SMT component  (MMA7456L Accelerometer)



I started by creating the design of the breakout board  PCB you can find the PDF here LGA14_BREAKOUT_BOARD.pdf.

Next I printed it on a piece of tonner transfer paper. To save transfer paper I first printed the design on a regular sheet of paper , then I cut a piece of transfer paper and taped it to the white sheet. Make sure you leave enough border – you don't want to print on the tape. After that the paper is fed again into the printer and the design is printed on the transfer paper this time.


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Soldering a wire to fine pitch (0.3mm) SMT devices

In this tutorial I will describe a technique for soldering to fine pitch SMD pads. Using this approach I was able to solder a wire to a 0.3mm (~ 12mil ) pad.

1) Start by tinning the pads:

– place liquid flux on the pads

– take a "ball" of solder on the soldering iron tip and gently touch the pads, if you get to much solder connecting the pads, just "wipe it off" with a clean soldering iron

– the pads that have fresh flux will attract the solder

– the tinned pads should have small "pillows" of solder on top of them.

2) The wire should be thinner than the pad. You can get a thin wire by separating a thicker stranded wire. Tin the wire the same way as you tinned the pads

– first place liquid flux on the wire

– next touch the wire with a soldering tip that has some solder on it

3) This is the main step, the main idea is to mask the pad being soldered with 3 pieces of temperature resistant tape (Kapton tape).

The setup looks "dirty" when magnified, because of the sticky flux, you clean it up usually at the end with alcohol.

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Reverse Surface Mounting of Small Leadless SMT Components

This method of surface mounting is unconventional and is not recommended for production projects. If you plan to use the device in a mobile project make sure you seal it.

It's a know fact that the surface mount devices are becoming more and more popular leaving behind the traditional through-hole mounting method. While for the electronics industry surface mounting brings a lot of benefits (one of them being the ability to pack more components per square inch) for the regular hobyst surface mount devices are often times a "show stopper".

This tutorial is for those of you who absolutely need to mount a small surface mount device for prototyping purposes and do not have the means or time to perfom a traditional surface mount. There's obviously a "correct" way to mount a SMT component and I highly recommend reading the Surface Mount Soldering guide at Curious Inventor first before attempting this method. However it's always good to know that there's an alternative method that does not require any investments in expensive SMT equipment or materials.

In this tutorial I'll describe how to mount an analog LIS244AL accelerometer (data sheet), that comes in a tiny leadless LGA-16 package. The size of the component is 4x4x1.5mm. It has 16 solder pads, each is 0.3×0.4mm. This is the tinest component that I ever have to deal with. When I first saw this device my first thought was that there's now way I can mount this little device without creating a custom PCB and using the traditional surface mounting method.

After several trials and errors I came up with an interesting method that uses masking tape in order to create bridges from the device pads to the pcb regular "through-hole" pads. I also made my work easier by bringing the device pads to the same surface as the PCB hole pads.

No custom PCB is required for this tutorial, we'll use a regular proto-board that you can find in any electronics shop. However you can create a custom PCB to minimize the distance between the device and the external pads.

First mark the desired size on the board that you'll use for your breakout board. We'll use a piece that has 4×4 holes (two pieces are marked on the picture below).

proto board

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