OT: Christmas project with the kids

I managed to heat up the soldering iron and melt some solder during the weekend before Christmas, but it wasn't in pursuit of anything ham radio related.  I have a RockMite kit that I've been meaning to get to, but never seem to get around to it.  But no, this weekend's project was done with and for the kids.

While bumming around Radio Shack a few weeks ago I stumbled across the neatest little Velleman 3D Christmas tree kit!  It didn't look to complicated and was only $7 so I decided to give it a shot with the kids.  Now keep in mind, my kids (the two that were most interested in helping) are 7 and 10 so I couldn't do anything too complex, but this looked right up their alley!

Just like the last little project that I did with the kids, they are still too young to solder, but they can sort parts by type, sort resistors by color code and now they are old enough to actually put the components onto the board as well!  This kit comes with two boards that makes of the planform shape of a Christmas tree.  This worked out perfectly as each kiddo was able to get one board to work on.

The project did not require much in the way of tools.  A soldering iron, some solder, and some snips.




























Our process was this:

1. The kids sorted out the components into groups together (capacitors, resistors, transistors, etc).
1. My youngest daughter, the eldest of the group at the bench, took on the task of sorting the resistors by color code, learning a bit about said code in the process.
2. Each kid got a board, and with some help from Dad found the marked locations for each component (resistor X goes into the R1 location).
3. They then bent the legs of the components so that they would fit into the holes in the board.
4. As one kiddo got a part mounted, Daddy would solder it on and trim the excess off.  By then, the next kiddo would have a part mounted and the process would continue.
5. We continued on in this vain until all of the parts were on the board (first resistors, then capacitors, then transistors, and finally LEDs).
6. Once that was done, Daddy soldered on the battery leads and joined the two halves together with jumpers (the hardest part of the project).

All in all it was a fun little project that took about and hour and a half from start to finish, and we ended up with an ornament that we can use for many Christmases to come!  

Here is a shot of the eager little technicians that help during the build out, along with the fruit of their labors:

And a close up of the finished tree:

And a couple of shots with the lights off to show the blinking motion of the LEDs:

This was a fun little project and helped to keep the kiddos entertained while Mommy was a work!  I hope to get back to some radio related projects in the near future, like maybe that RockMite kit, or installing a 4BTV vertical, or building a 12el yagi for 2m, or a "turnstile" moxon for satellite work on field day, or you get the idea...  Maybe during some vacation time that I am planning on taking in January...  Time will tell.

Merry Christmas and Happy New Year!

73,

Richard, KK4JDO

Rainy afternoon project with the kids: Coax Tester!

After finishing up the souncard interface yesterday, I thought that I would be done for a few days, but a house full of boisterous kids on a rainy day dictated otherwise.  As they say, necessity is the mother of invention, or in this case, maintaining my sanity was...  ;-)

I recalled watching a YouTube video by W5CYF (Tinker John) on how to make a simple go/go-go coax tester.  It seemed like a good project for the kids and I to do.  Like John, I used a green LED to mean the coax is bad, but hey, it's what I had on hand.

This is a simple, quick and dirty schematic of what we built:

In a project list this, there are a few things that kids can do, and a few that an adult needs to do.  While watching the kids play with the drill or soldering iron would be entertaining in a scary sort of way, the trip to the hospital afterwards would have been annoying.  However, seven year olds are good at sorting resistors by color, and 9 year olds are good at tightening screws.  They are also both helpful when small parts are dropped by fumble fingered parents.  Just remember that kids are kids, and tend to be distracted and not remember the goal.  They also like to fidget A LOT.  My son got to spend a few minutes in his room due to this, but he settled down and was back for the finish and testing.

My Parts List:

• 1 x SO-239 connector
• 1 x 9V battery connector
• 1 x 350 Ohm resistor
• 1 x Green LED
• 1 x Small project box
• 1 x 7 year old boy
• 1 x 9 year old girl

Time to Completion:

• About two hours, after all, the kids were helping me!  ;-)

Here are a few pics:

Here are the two proud builders!

Picture of the tester.

In this picture, I used a small bit of solder to simulate a piece of bad shorted coax.  Notice the green LED is on.  Green usually means good, but in this case, green is NO-GO!

Again, this was a fun little project that will give you an absolute basic go/no-go test of a piece of unknown coax.  It won't tell you impedance or length, if you need those tests go get an MFJ-259B or something similar.  If you want to make sure that you don't have a dead short and won't blow up your finals, this is the tool for you.  ;-)

73,

Richard, KK4JDO

Soundcard Interface for APRS/Packet - Part 2

Well, I finally got the PTT part of the soundcard interface working.  This was fun, and sometimes frustrating, but very educational.  I am lacking in my understanding of component level electronics engineering.  As a network engineer, I would be comfortable designing and implementing an enterprise network for a new hospital (that's a different story), but understanding why a transistor works the way it does is beyond me at this point.  So I kind of fumbled my way through this.  One thing that is very important in network engineering is attention to detail, and solid planning.  For some reason I didn't carry this over to this project, and it bit me..lol

Let me state, for the record, plan your work, and work your plan.  Don't just wing it.

Okay, on that note, on to the project.  Once again, soundcardpacket.org was a great source of information on getting this part working.  I used this schematic from their site (click on the image to see more details):

R1 = Resistor, e.g. 1K2, to reduce voltage on the IC pin 1

IC =  Integrated Circuit; this sketch shows an IC, such as a 4N33

        or PS2603 Optocoupler, which uses a Darlington pair transistor.

        (Note: to identify pin #1, look for a small embossed circle on

         the top of the IC above pin 1; or looking into the notch in one

         side of the IC with the pins down, pin #1 is to the right of the notch.)

D1 = Diode, e.g. IN4001, would shunt any potential reverse voltage

        that might damage the sensitive diode/emitter in the IC.

        (Note: the band printed on the diode marks the cathode end,

        which attaches to the Serial Port/IC Pin 1 line in the sketch above.

        The opposite/anode end attaches to Ground.)

In the last post about this project, I built the receive and transmit cables that connect the output of the radio to the input on the soundcard, and the output on the soundcard to the input on the radio.  This worked well for listening to APRS and packet conversations, but I couldn't join in without manually keying the mic, which works okay if you're doing PSK31 or other HF digital modes, but isn't as easy with packet or APRS.  With this addition, a signal is sent via the PC's comm port to key the PTT circuit on the radio.  This allows the radio to be keyed via software instead of manually.  This allows things like APRS beacons to work normally.

This particular design uses an optocoupler to isolate the radio and the PC, while still allowing communications to flow.  This, along with the audio transformers used in the last post, helps to eliminate ground loops and voltage differentials, which are a source of hum in your transmission audio.

While building my version, I found that I didn't have the required 1.2K Ohm resistor, so I substituted a 1K and a 220 Ohm resistor in series.  This took a little additional space, which was at a premium in the tiny project box that I used, but ended up working well.  As you'll recall, in the last post, I decided to build this in a project box, instead of as a set of cables.  I think that in the long run my way will be more durable since there will be less movement of the internal solder joints due to cables wiggling around.  Time will tell.

A couple of issues that I ran into:

1. On Windows XP (need to upgrade my shack PC), the serial mouse driver keeps the RTS pin HIGH, which causes the mic to key if nothing has taken ownership of the comm port that you are using (AGWPE, Digipan, etc) to bring it LOW.
2. The pinout of the IC that I used was different than the one pictured in the schematic, don't blindly trust any schematic, do your homework first.  It saves solder (and frustration)
3. Don't use too small of a project box, it is easier to do things if you have the room to do them in.

A couple of lessons that I learned:

1. When if doubt, check solder joints.
2. Follow the voltage, step through the circuit with a multimeter and make sure that you are seeing what you expect to see.
3. Amperage kills...  This applies to ICs and other components as well as people.
4. Be sure that the part is installed correctly BEFORE soldering...  

My Parts List:

• 1 x 4N33 Optoisolator
• 1 x 1K Ohm resistor
• 1 x 220 Ohm resistor
• 1 x IN4001 diode
• 2 x 1/8" mono audio jacks
• 1 x 6-pin mic connector to interface with my TR-7730

Time to Completion:

• This part took me about eight hours due to lack of understanding and being too trigger happy with the soldering gun.  Next time should go smoother as hopefully I have learned my lesson on this.

Here are a couple of pics:

The IC and diode on the bottom right, and the two resistors on the bottom are all that make up this part of this circuit.  The other two resistors and the two transformers are for the rx and tx circuits.  You can also see the two audio jacks that I used to connect the PC and Radio.

This shows the completed and closed project box.  Again, while I at first thought that smaller would be better, after building it, I should have used a slightly larger box.  The next one that I build will be a bit bigger.

These are the cables that I built to connect the computer to the project box, and then on to the radio.  The gray DB9 connector attaches to the comm port for RTS based PTT.  The other end of that cable is an 1/8" mono connector that attaches to the project box.  The 6-pin cable actually has two pig-tales, one 1/8" mono for audio, and another 1/8" mono for the PTT signal.

And here is a shot of the APRS terminal showing me sending and receiving traffic.  I need a better antenna to hit more than one or two stations directly, but thankfully, one of the stations that I can hit is a digipeater/IGate.

All in all this project was a lot of fun and extremely educational.  It is also a LOT cheaper than buying another SignaLink.  I think that I have around $20 invested in this, plus my time.

73,

Richard, KK4JDO

Soundcard Interface for APRS/Packet

Happy 4th of July to all of my American visitors (and also to everyone else, although I don't imagine that it is quite the same).  Not that I have that many visitors from anywhere, but it's the thought that counts.  It's been a few days since I posted anything, so I wanted to get this up on the site.  I've been enjoying my SignaLink USB soundcard interface for digital modes on HF, but I would like to run APRS on the same PC, and running two SignaLinks with APRS can be problematic.  Besides that, I didn't want to spend another $70 to $100.  So I decided to build my own interface.  There is a great resource for this at: http://www.soundcardpacket.org/.  They walk you through the build options and troubleshooting if needed.  That being said, I've borrowed their schematics to post here (full credit for the schematics goes to them).

For this interface, you will need three connections, one for receive, one for transmit and one to activate the PTT switch on your radio to allow the transmission.  I am 2/3 of the way there.  I have the send/receive portions complete, and am waiting on the parts for the PTT circuit (it requires an opto-isolator, which I couldn't get from Radio Shack).

I tested the receive and transmit using DM780, which is part of the Ham Radio Deluxe suite, and was able have a QSO via PSK31 on 14.070MHz (manually keying the mic, which is annoying).  That being said, it seems to work well, and hopefully the parts will be in soon for the PTT portion.

Here is the schematic for the receive cable.  The radio that I am using (old Kenwood TR-7730) does not support audio out via the MIC at line-level, so I opted for the 1000:8 transformer to allow me to use the speaker out jack on the back of the radio:

And here is the schematic for the transmit cable:

These are fairly basic circuits and do not require a lot of time or effort to build out.

My Parts List:

• 1 x 1:1 audio transformer (transmit cable - RS Part #274-1374 - these are getting scarce)
• 1 x 1000:8 audio transformer (receive cable - RS Part #274-1380)
• 1 x 100K Resistor
• 1 x 1K Resistor
• 2 x mono audio jack
• 2 x stereo audio jack

Time to Completion:

• This one took a few hours to put together, but quite a bit of time finding the right transformer.

Here are some pics:

(I nabbed the TR-7730 pic off of the net, but it looks identical to mine)

I decided to build this out as a stand-alone box with audio jacks instead of as a set of cables for neatness.  I'm an engineer by trade, and am rather stuffy about how wiring looks.  Stay tuned for the next installment in this post when I get the parts in the complete the PTT circuitry. 

73,

Richard, KK4JDO

Update to the PTT Mic via USB Project

So since I've gotten into trying to learn Morse code, I needed some type of oscillator, so that I can hear my key as I practice.  You can purchase an oscillator from companies like MFJ, or you can make the on the cheap with a piezoelectric buzzer and a 9v battery.  I chose a slightly different route.

My option was to add a 1/4" jack to my PTT desk mic via USB project box.  I did keep the piezo buzzer in case I wanted to practice without interacting with the PC, but I am currently using a program called MorseRabbit, which can accept input from the keyboard spacebar.  Only, in this instance, the input is coming from my straight key, which in turn is connected to the Teensy USB microcontroller, which is emulating a keyboard.

My Parts List:

• 1/4" mono audio jack (panel mount)
• 5v piezo buzzer
• bit of wire and solder

Time to Completion:

• 30 minutes, including adding the necessary code to the "sketch"

Here is a pic:

Here is a copy of the code "sketch" that I am using:

#include <Bounce.h>

Bounce button0 = Bounce(0, 10);

Bounce button1 = Bounce(1, 10);

void setup() {

  pinMode(0, INPUT_PULLUP);

  pinMode(1, INPUT_PULLUP);

  pinMode(12, OUTPUT);

  pinMode(14, OUTPUT);

}

void loop() {

  // Update all the buttons.  There should not be any long

  // delays in loop(), so this runs repetitively at a rate

  // faster than the buttons could be pressed and released.

  button0.update();

  button1.update();

if (button0.fallingEdge()) {

   // press and release CTRL

   Keyboard.set_key1(KEYPAD_PLUS);

   Keyboard.send_now();

   Keyboard.set_key1(0);

   Keyboard.send_now();

   analogWrite(12, 200);

  }

 if (button0.risingEdge()) {

   // press and release CTRL

   Keyboard.set_key1(KEYPAD_PLUS);

   Keyboard.send_now();

   Keyboard.set_key1(0);

   Keyboard.send_now();

   analogWrite(12, 0);

  }

  

if (button1.fallingEdge()) {

   // press and hold space

   Keyboard.set_key1(KEY_SPACE);

   Keyboard.send_now();

   analogWrite(12, 200);

   //analogWrite(14, 255);

  }

 if (button1.risingEdge()) {

   // release space

   Keyboard.set_key1(KEY_SPACE);

   Keyboard.set_key1(0);

   Keyboard.send_now();

   analogWrite(12, 0);

   //analogWrite(14, 0);

  }  

}

You have to forgive the sloppy wiring, it was too much hassle for this project to etch a pc board.  Now I have the ability to practice CW on my PC, both sending and copying!

73,

Richard, KK4JDO

Fun Project with the Kids

Here is a fun little project to do with kids.  It is also educational.  This was done a few years ago, but we still have fun with it from time to time.  This is a simple electro-magnet built by winding some copper wire around a steel screw, and connecting it to an electrical current (low voltage provided by some "AA" batteries) via an on/off switch.  I stuck a little LED in there to show when it was turned on, not that it was needed with a switch that was labeled, but it was fun.

My Parts List:

• 1 x Project Box
• 1 x 6' of copper wire
• 1 x Screw
• 1 x SPST switch
• 1 x LED (with resistor built in)
• 1 x power connecter (really not needed, batteries could be inside of project box)

Time to Completion:

• About four hours with the "help" from the kids.  ;-)

Here is a pic:

Just a fun little project.  I'll work on getting some pictures of it in use.

Thanks,

Richard, KK4JDO