Tuesday, May 27, 2014

Minima - Audio Module

I have made further Revisions to my Experimental Minima Transceiver Audio Module (see previous post). I still do not exactly enjoy building Audio circuits, but it needs to be done.

I have modified the original circuit to peak my interest. My circuit will incorporate (among other things) some AGC and a little more available Speaker Power. But of course, none of this has been tested and therefore operational results may be different than expected.
My Planned Minima Audio Module
This board will be 2.5x5.0 inches with 84 via's, it is not very dense, because the layout provides a human interface with normal finger spacing, and it is also size to plug onto my other Minima Modules.

I will make the first Prototype board with the Toner Transfer Method (TT) to check operations.

Unfortunately, I will be busy the next few days will not have much time to work on this project.


Sunday, May 25, 2014

Saturdays Projects

Yesterday, Jeff - K07M stopped by and we worked on some projects.

Jeff wanted to practice welding. I have both TIG and MIG welders, so we spent some time "gluing" some Aluminium together with TIG, and then some steel with MIG. With a little practice Jeff was able to "lay down" a reasonable bead. Welding is a "art", therefore practice is almost always necessary to stay proficient.

We then moved into the E-shop where we diagnosed the failed BusPirate (see previous post), we quickly isolated the problem to one pin of the Microprocessor (PIC24FJ64GA). I suspect that the failure was the result of an ESD (Electrotatic Discharge). The failed pin is directly connected to a clip lead on the end of the test cable. I have been a little lax regarding ESD abatement in my E-shop. I need to acquire a bench-top anti-static mat and maybe some anti-static floor spray.

A last minute project before Jeff left, was to "fix" my long-wire antenna haul-up cord used for the end support over the tree. The long-wire has been up for two years and therefore the support cord has (most likely) cut into the limb, and then the tree has retaliated with pitch to glue it in place. Regardless of the tree's desire to hold the cord in place, I need it to be free for Antenna adjustment or configuration changes. I had attempted to bring down the Antenna before, but could not pull hard enough to break it loose.

Our goal was to pull until; the limb broke, or the sap let go, or the cord broke. After wrapping the cord around a 2x6, like oxen, we were able to pull it free. The cord is tied into a loop, so that I can pull-up or pull-down as necessary. To alleviate future problems, we inserted the cord into a twenty foot section of 1/4 inch Polypropylene Tube (refrigerator ice-maker tube), tied a knot and pulled the tube up and over the branches where the cord rests. Hopefully the 20 foot section of tube so draped over the branches will stay in place, and protect the cord from the tree.

The 300 foot long-wire is now again at about 90 feet AGL.

Thanks, Jeff, for the help !

When I wrote this blog entry, I did not realize Jeff had blogged the same project day, check it out at: http://goo.gl/LuZE0S  :-)


Friday, May 23, 2014

Clip Leads

For the last several days I have struggled with toubleshooting some very small circuits (see previous post). Thanks to my friend Jeff - KO7M, troubleshooting was successful.

A part of troubleshooting is; measuring, stimulating, and configuring the Device Under Test (DUT), to do that jumper wires and clip leads are needed.  Over the years I have collected a "rag-tag" set of clip leads, but most are only useful for larger circuits. The few small clip leads that I have were enlisted in the recent troubleshooting effort, where only a few of those clip leads were from a matched sets.
BusPirate Prob Set

For the BusPirate I use an Adafruit.com Probe Set with 10 hooked clips on one end, which is very handy to make connections to the DTU.

Even though Jeff did not have difficulty, I found trying to clip the additional external Pullup Resistors, and test equipment on to my small board was a challenge, some of the header pins required more than one clip lead and the spacing between pins made the it even more challenging.

Pomona 5790-0 Micrograbber
By chance, one of the clip leads that I had was a Pomona Micrograbber, it seems like I have had this clip lead forever. but I had never really used it.

In the tangled mess of wires and clip leads around my DOT I found the Micrograbber most useful. It has two ports for removable wires and its claw seems to require much less space on and around the Header Pins.
Adafruit Jumper Wires

These clips can be connect with jumper wire that have square female ends. This type of jumper wires are available in several lengths from Adafruit.com.

I now really like these clips.

At the time, I did NOT know the manufactures name or a source to obtain additional Micrograbbers, they are only embossed with the letters "dli".  Google search did not provide any clues.  Additional search for "micro clips" put me onto the right path to Pomona, where I found the name and part number. They are available in Black (5790-0) or Red (5790-2). A quick check with Mouser.com and Digikey.com gave me the order number and the PRICE! They are about $9.00 each. Yikes ! A few are available on ebay.com but they were even more expensive (go figure?).

Yes, I know, very small "hooked clips" are available that are very useful (I have a few), but they are not as configuration flexible, and they are typically connected (soldered) to wires and at a fixed length. With hooked clips, connecting more than one wire generally means a second (or more) clips on the same pin. With 5790 Micrograbbers, two wires can be connected on each.

I now have four (4) Pomona 5790-0 Micrograbbers on order, . . . but I really wished they were a little cheaper!

A local group-order could save a few bucks on each and the shared postage, . . . anyone?

Note: The above Images were obtained without permission from their respective web sites, hopefully the owners will not mind the inclusion here for this endorsement.


Wednesday, May 21, 2014

Minima - VFO Troubleshooting - Cont'd 3

After four days of extreme frustration, while troubleshooting my Minima VFO Module (see previous posts), there is success!

My friend Jeff - KO7M came by today with known working tools (BusPirate) and parts (Si570). We had been troubleshooting my VFO problem via e-mail and over the phone, but we were not getting anywhere.
Jeff at the Microscope
The problem came down to, two (2) simultaneous failures, one in my BusPirate (BP) and one in my VFO Module that I was testing.

1. My BusPirate fails to generate I2C SCL (clock) signals, even though many other functions seamed to work. Without an SCL signal data can not be received by a Device Under Test (DUT), even though the BP can receive Data using the same SCL wire from the DUT.

2. The failure of my VFO was the Si570 itself, it would not accept I2C data or commands, even though it produced RF on the output. It is DEAD.

Before Today

Before today, I had created an Si570 BreakOut Board (see previous post), with just the Si570 and Header pins. My intent was to verify that the BP was working as expected, but because there are also wires, clips and connectors that could have failed results were inconclusive.
Si570 Breakout Board
Si570 Breadout Board
At this point I still could not determine if the failure was in the BP or had I damaged another Si570. So, I built a second Si570 Breakout Board. But alas, still nothing seemed to work.

Today - Jeff to the Rescue !

With Jeff's known working BP we quickly determined my VFO Module (i.e. Si570) was bad. Other I2C devices; the two Si570 Breakout Boards and a Real Time Clock Module (RTC) all work as expected.

Because yesterday I had used my last Si570 on the second Si570 Breakout Board, I could not repair the VFO Module. but we could build an Si570 Breadout Board Adapter  that connects between the Breakout Board to the Minima CPU Module. I had previously designed and did a layout for the Adapter with DipTrace, for just such an occasion. We spent the rest of the afternoon building and testing the Adapter Board.

The Adapter Board tested correctly with Jeff's BP as we hoped. It also tested and worked with the Minima CPU Module.
Adapter Board Connected to the Minima CPU
and a Coax Cable, the Si570 Breakout Board in the Foreground
Stacked and Ready for Testing
Now all Minima Modules worked as expected, we checked for a varying frequency while tuning, we estimated on the oscilloscope 20MHz at the low end, and 50MHz and the high end while Tuning across the (0-30MHz) HF band (for a 20MHz IF).
34.2MHz  (14.2+20) As Shown
with 10X Expanded Sweep Scale
Minima CPU Module and
Temporary VFO Module 
I am a happy camper - Thanks Jeff, for the help !

I can now continue my experiment Minima Transceiver Project.

I need to order a few more Si570's, and a new BusPirate (or troubleshoot and fix it).


Sunday, May 18, 2014

Minima - VFO Troubleshooting - Cont'd 2

Well, that did not work, see previous post.

I created a Si570 BreakOut Board with minimal configuration to have something that I can test and verify my BusPirate. I got the same results with the new board, the I2C Address Scan returns nothing.

I must have something wrong with my use of the BusPirate.

The Si570 BreakOut Board that I created is a little different than previously posted, it now will fit in a standard 600mil socket. Which means that it is a little bigger than the original 500mil config, but should be more useful.

Here are some of the build details.
The New 600 mil Layout
As Designed with DipTrace
The size of the board is about 0.5x0.7 inches and is 0.032 inches thick, with four via's (40mil pads, 10mil holes).

You can almost see through the PCB material, the two sided image alignment is reasonable.
A Panel of 
Double Sided Toner Transfer PCB's after Etch
(Showing the Back Side)
This is the results after: Cut, Solder Wipe, Holes Drilled, and Parts Loaded.
The Finished Si570 BreakOut Board
When I get the BusPirate operational issue sorted out, this should provide a simple verification test. It will also be a useful part for ProtoBoard experiments.


Minima - VFO Troubleshooting - Cont'd

Regardless of what I have tried, my Minima VFO Module does not seem to work, see previous post.  It does not respond to a simple I2C Address Scan from the BusPirate (BP). The problem could be a something simple on the VFO Module, a dead Chip,  the BP, or the connecting wires. I could test the BP and wires if I had a known working I2C device, but I don't.

To fix that, I am going to build a simple stand alone Si570 BreakOut Board, which will only contain an Si570 and Header Pins. If this works, it will be useful for verifying my BP and also it will be useful for other standard ProtoBoard experiments.

Proposed Si570 BreakOut Board
A simple Google search did not suggest a consensus of pin outs for a breakout board, I decided to arrange the pin in Si570 documented order similar to a DIP. The board will be about 0.5x0.6 inches. I guess I should have made the pin row spacing 600mils (not 500mils) so it would fit standard PCB DIP Sockets.

Using standard pin order requires a trace on the backside with the accompanying two via's. Two additional via's will help tie the front and back ground planes together. All soldering for the Headers will be done on the top side, because Homebrew boards do not have plated through holes, and therefore it would be difficult to solder under the Headers on the back side.

I could have included the two required I2C Pullup Resistors, but no, I wanted this to be a generic as possible.

This maybe a very useful board for my future projects, it is a simple task to make several copies while making the first, using the Toner Transfer (TT) Method.


Saturday, May 17, 2014

Minima VFO - Troubleshooting

Last week I was on Jury Duty, and therefore there was little or no time for my Hobby Projects.

But now, I need to continue troubleshooting my Minima VFO which is reporting an error on the LCD display. The error at program reset is: "Si570 comm error".

As programmed, the Arduino Sketch seems to ignore the error and continues with normal execution. If I remove (unplug) the VFO Module the program "stops" and does not get past the initial start-up stage, and therefore it appears that there is "some" communication with the Si570 (or at least the Pullups work).

My friend Jeff - KO7M, suggested using my BusPirate to ensure that the Si570 was set on the correct I2C address as published and working as expected. This will be easy because of the modular construction that I am using, tests can be conducted on only the VFO Module. This testing would be much more difficult (but not impossible) if everything was built on a single board.
Minima VFO connected to the BusPirate
I am glad I blogged my previous use of the BusPirate, it helped me to remember the commands. I think I will expand that post to be more complete.

Well, maybe it is NOT so easy, because so far, I have not found the VFO problem. In fact, I do not seem to be able to do a simple "scan" for the I2C address.

More troubleshooting needed !


Thursday, May 1, 2014

Minima VFO - Under the Microscope

I have been doing some troubleshooting of my Minima VFO, for some reason it is not "talking" with my Minima CPU module. My friend Jeff - KO7M as provided some suggestions for resolution that I am working on.
My Minima VFO
As Built
Just for fun, I took some Microscope Photos while reviewing the circuit and PCB layout for errors. Here are a few for your review.
From Pins 4 and 5 Perspective

The 3.3 Volt Regulator - SOT-89-3
and Its Output 0805 Filter Caps

Power Indicator with its attending limiting Resistor
The Resistor and LED are size 0603

Binocular Core Output Transformer
This is 32 AWG Wire

SMA RF Output Connector
I enjoy working under the Microscope, there are many things that otherwise we would not see.


Minima - Audio Circuits

With my prototype Minima CPU Module working (see update at bottom of a previous post), I have returned my attention to the Audio sections of the Transceiver. But, I still do NOT enjoy building Audio circuits - the capacitor are just too big :-).

For me, audio circuits are as boring as power supplies.

But, maybe there is room for some adventure and intrigue by implementing an alternate circuit with some very small modern parts. Also, there may be an opportunity to multi-purpose some of the circuit elements. I am just now starting to explore this idea. What ever I build, it will be compatible with the original Minima circuit.

More information will follow.

I will probable eventually build the Minima Audio circuit as originally published.