Sorting, sorting , sorting

Usually I store my resistors in a zip bag and there is always the worry  if I already own the right ones for a certain project.

More than a year ago I bought three smd component storage boxes and started to sort my 0603 resistors.
First you have to label all the compartments and then you fill them up with resistors.
Great care is to be taken, wrong placed resistors have to potential to sabotage you project.

Sorting the 0603 resistors was really not a project you would write home about.
But the resistor box turned out extremely useful.
In fact so useful I would not miss this box anymore.
By the time (> 1 year at least) I also forgot about all the hassle.
So I decided today it is time to fill another box, this time 0805 resistors.
To get an idea of the project, i own meanwhile more then 10k of 0805 resistors with about 170 different values.Eight back aching hours later, I finally sorted them in !!!

 

Very useful storage box

more than 10.000 sorted resistors

How to solder QFN chips like the MSP430FR5739

The new MSP430FR chip line has interesting features like embedded non volatile fram and ultra low power consumption. The chip is available in TSSOP38 or QFN40 package.I simply had to try them out.

Usually hobbyists  are repelled by the very small case and the missing pins.
But once you get used to work with the QFN package you start to prefer it over any other packaging.
Since they have no visible pins, they cannot suck the solder up via capillary suction and create ugly shorts.

To solder a qfn chip you buy a breakout board and put a small amount of solder paste at the pcb.
Beside the solder paste you add some solder flux (very important).
Then you place the chip on the board and roughly align it.
With an heat gun you slowly heat the chip and board until the flux starts to melt.
This is a very important phase because the chip will swim on the fluid and align itself correctly.
Now heat it up until the solder past melts and you are done.

The next problem you will face is how to check the correct alignment and if all pins are correctly connected to the board.I use a multimeter for that purpose. Usually the pins have a certain resistance around 5k to 1mega ohm. Measure all pins and if there are shorts suck them away using some solder wick.

Once you get used to Qfn packages and are able to solder the chip  correctly it will only require about two minutes of your precious spare time. Soon you will start to enjoy working with Qfn packages.

MSP430 in QFN package compared to a Dil20 chip

Links
MSP430FR5739
Fram
Demo video

Meet the Powerscope

Since Ti announced the Launchpad I was very excited to play with this awesome development tool.
It is like a Arduino on steroids, mostly because of it's 16 bit capability and most important it has a debugger.
When your code does not work nothing is more useful than a debugger, maybe  with the exception of a razor sharp brain and years of development experience might not hurt either.

Since the Msp430 line supports low energy consumption and have many different feature sets it is important to verify if the consumption is really as good as it could be. To see exactly what is going on, a scope is the tool of choice, but for a quick estimation the Powerscope is much more comfortable and easier to use.

When measuring very low power devices I would not recommend to use a multimeter, because of their usualy high burden voltage. To circumvent this problem, David Jones from EEVBlog designed the uCurrent , also a great tool.
The Superprobe is a somehow similar device, but it has it's own display so you don't need to connect it to a multimeter.

I also built an usb adapter to attach the Powerscope to a Usb device and measure it's power consumption.
In the attached example pictures I connected the Powersope to an Launchpad which drove a CC2500 radio device.It does not make much sense, because the attached debugger also has a unknown power consumption but it gives an idea of usage and it also shows that the TX mode consumes about 17 mA more than the RX mode .Btw. the code in the moment has no power optimisations what so ever, I was more than happy to get the CC2500 up and running,...

The programming of the Powerscope also was more than easy.
You can either use the Launchpads programmer by removing all the jumpers and insert a programmer cable or you can like me use a Goodfet programmer designed by Travis Goodspeed.
Since I don't like to solder headers just for one time programming, I made a small programming cable with pogo pins. You can use this kind of connection even for debugging.

You can buy an empty pcb at the 43oh store.

Powerscope front side

Powerscope back side

Powerscope connected to Lauchpad in TX mode

Powerscope connected to Launchpad in RX mode

Goodfet 4_1 programmer and programming cable with pogo pins

Links:

Buy Powerscope pcb
Designer thread
Powerscope Code and Info page
Goodfet programmer

Spectrum analyzer Part VII The Frame

To be able to test the modules and later insert them in a proper case they have to be secured somehow.
Scotty suggested a double sided raw pcb and to cut holes into it where the future modules will be placed.

Since I did not have such a pcb in my stock but was fortunate enough to find some brass profiles I used these to build my frame.

I cut them to size using the following template on Scotty's website and hardsoldered them.
Unfortunately  they get pretty messed up during the soldering process.
To clean them up you have to bath them in a 40% sulfuric acid solution and wipe them clean afterwards using a polishing cloth.
The last step is to drill mounting holes into the frame's edges.

Frame after soldering

Frame after cleaning

 Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector
Spectrum analyzer Part III ADC 16
Spectrum analyzer Part IV Logarithmic Detector  
Spectrum analyzer Part V Master Oscillator
Spectrum analyzer Part VI DDS 

Spectrum analyzer Part VI DDS Module(s)

Description (copied from Scotty's web page)

The DDS module is designed and configured with a filter and squaring circuit in the DDS A path.  The filter shown is a 10.7 MHz crystal filter with a 15 KHz bandwidth.  
The squaring circuit of U3 will output a CMOS level, capable of driving a 50 ohm line (J4).  
J3 output is an unfiltered output of the DDS B and will contain all harmonics and aliases of a normal DDS output.  Its output power level is approximately -8 dBm.
For best results, the Clock Input at J1 should be a 5 volt peak to peak square wave, but it will operate at a much lower input.  R3 determines the input impedance of the module.  The input clock frequency must be between 1 MHz and 125 MHz, although the AD9850 is somewhat underrated.

Build process

Soldering the dds chip is somewaht tricky, good magnifying glasses are a must.
Since the DDS chips are serially programmed, I use a different pcb (which I got in a group buy) with only 5 inputs.I think it was routed by Sam Wetterlin but I am not sure.
Studying the schema carefully is highly advisable since there is always a chance that components are placed in a different location.
Because I am building the complete" analyzer, I had to solder two of this modules, the second one is used in the tracking generator.

One of the coming blog posts will be about testing the DDS module and how to shield a Slim module properly.

DDS module rev D with serial input only

 Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector
Spectrum analyzer Part III ADC 16
Spectrum analyzer Part IV Logarithmic Detector
Spectrum analyzer Part V Master Oscillator

DDS Module

Spectrum analyzer Part V Master Oszillator

Description (copied from Scotty's web page)

The Master Oscillator, contains a 64 MHz oscillator and 3 buffered line drivers.
Each output is 5 volt CMOS that can drive a 50 ohm line that is terminated with either, a high impedance load, or 50 ohms.  A 33 ohm resistor is shown as a series element in each output.
The frequency will drift with temperature. I was able to test only one sample. It had a positive frequency/temperature coefficient of .15 parts per million per degree F (9.6 Hz / 1 deg F)

The build was fairly easy you just have to take care of possible cold solder joints around the crystal oscillator. This kind of packaging easily produces cold solder joints.

Since the unit is already tested I already shielded it.

Master Oscillator rev B

MO back side

Side view of shielded oscillator

 Links:
Spectrum analyzer Part I Controller board Spectrum analyzer Part II Phase Detector   Spectrum analyzer Part III ADC 16 
Spectrum analyzer Part IV Logarithmic Detector 

Master Oscillator 

Spectrum analyzer Part IV Logarithmic Detector

Description (copied from Scotty's web page)

The 8306 Log Detector Module has a dual function.  It is used as a detector to convert RF power to DC voltage (RSSI).  And, it is used as a high gain, RF limited amplifier.
The module has an input impedance of 50 ohms (J1) and a bandwidth of  3 MHz to 160 MHz.  
The RSSI dynamic range is -90 dBm to +10 dBm, with a DC output of +0.4 volts to +2.4 volts, on J2, "MAGVOLTS".  The Limited I.F. Output (J3) is a 50 ohm source with 50 mv peak to peak output.  
The limiter input dynamic range is from -77 dBm to +10 dBm.

Log Detector Rev 0

Build process

So far the Log Detector was one of the easiest modules to solder.

The only problem was to get hold of T1 but fortunately Coilcraft was kind enough to send me two pieces.

Once the module is thoroughly tested and confirmed working it is very important to shield this kind of units properly. 

 Links:
Spectrum analyzer Part I Controller board
Spectrum analyzer Part II Phase Detector  
Spectrum analyzer Part III ADC 16

Log Detector Module