(Now a bi-weekly program)

April 23, 2013

Join the "CWTD Yahoo Group" for email discussion in between our bi-weekly sessions by clicking here.

1) Precision Arduino Clock with Remote 7-Segment LED Display
2) Tools for the Homebrewer's Workbench
3) Cool Product of the Month: Si4707 Weather Band and SAME Data Receiver


We cover three topics this week! ...

1) Remote 7-segment LED Display for the Precision Arduino Clock -- This installment of the Clock project combines the XBee RF link topic from last time with a 4-digit,7-segment multiplexed LED module to provide remote display of time for the radio shack.

2) Tools for the Homebrewer's Workbench and Workshop -- This collection of "essential tools" for the homebrewing workbench will turn you and your projects into a star!  Seriously, they are mostly inexpensive and every good homebrewer should outfit his shop with these basic items.  

3) Cool Product of the Month -- A new regular segment is added to our bi-weekly program, describing a cool new product for us homebrewers ... this time it's the Si4707 Weather Band and SAME Data Receiver.  Just think of the cool thinks we can do with this little board in out Ham Station Mesh Network ! ;-)

And once again we are pleased to have Frank N3PUU with us as a co-host!  Frank is quite the technology experimenter and it continues to be a pleasure for Joe and me to be working with Frank on our ongoing homebrewing platforms. 

73, George N2APB, Joe N2CX  &  Frank N3PUU

Podcast ... Either click on this MP3 podcast recording to play the podcast live on your computer, or right-click to save the mp3 file for local archive or later enjoyment.

Online Text Comments

Captured from listener posting in the text chat window during the program (comments relate to the live discussion at a given moment of the program) ...

<20:23:44> "John - NG0R (Mac)": does any one have a feel for who has the best price on xbee series 2 modules?
<20:24:37> "Charles WC5MC": http://www.wulfden.org/TheShoppe/freeduino/rbbb.shtml  wulfden RBBB
<20:24:52> "Bob - N2OJJ": I got my uno chip from virtualbotics on amazon for sub $5 and it came with the 16mhz crystal
<20:25:24> "Joe N2CX": Te Cheapest XBee soource seems to be Digikeu
<20:25:26> "Frank N3PUU": John, I find DigiKey has excellent pricing on Series 2 modules
<20:26:22> "Bob - N2OJJ": I also bought a bare diavolino board for $4.95 from evilmadscientist for another $5 and made a spare UNO with that chip
<20:40:20> "George - N2APB": Absolutely! There are several ways to go to lessen the cost of getting into the Arduino. The modules are available for those who either can't build it up from scratch, or those who don't want to take the time to do it. Either way is a good to go.
<20:42:08> "Alan W2AEW": If you watch the flyers in the newspaper, you'll often find you can get that same meter for FREE with any purchase. And it even comes with a battery
<20:42:28> "Bob - N2OJJ": I want to try plug cutter bits. the 1/4 in should be good
<20:50:36> "Pete - WB2QLL": Best way to start holes in metal where you want them 5pc center drill countersink set HF 42280
<20:50:48> "Bob - N2OJJ": most magazines have a 20% off coupon thats good to use for something big like that shear.
<20:52:42> "Pete - WB2QLL": The Stanley tin snip nowadays is also Chinese
<20:53:11> "Alan W2AEW": Look for Exelite brand hand tools - very nice
<20:53:43> "Alan W2AEW": oop, I think they're spelled Xelite
<20:53:53> "Alan W2AEW": or Xcelite
<20:56:11> "Alan W2AEW": If you do a lot of re-working, one of these is awesome! http://www.amazon.com/Hakko-Desoldering-Kit-With-808/dp/B000ARPULW/ref=sr_1_1?ie=UTF8&qid=1366764933&sr=8-1&keywords=haako+desoldering
<20:57:07> "Bill - KD5TFD": ditto on the Hakko 808 ... like an undo tool ... make ya fearless
<20:58:03> "Terry WB4JFI": For creating isolated pads on a PC board, I bought a Lenox 12158 hole saw kit. 3/8, 1/4, 5/16, & 3/8 size
<20:59:18> "Alan W2AEW": The first time i used the Haako-808 to desolder through hole parts, I nearly fell out of my chair when the parts I desoldered from a multi-layer through-hole board literally fell out of the holes. pain free!
<21:00:32> "Joe N2CX": Terry where did you get the Lenox hole saw kit?
<21:02:00> "Joe N2CX": Alan good point on using the hot air tool for through hole parts. Great ffor densely packed printed circuit boards!
<21:02:01> "Terry WB4JFI": I believe I got it through Amazon quite a while back
<21:02:16> "Joe N2CX": Thnaks Terrry I check it out.
<21:04:13> "Terry WB4JFI": The hole saws do not have a centering pin, so you have to be a little more careful about walking it on a board
<21:06:26> "Bill - KD5TFD": nice sdr project to decode the data on your pc ...
<21:07:33> "Joe N2CX": Terry I find that making the isolated pads is best with my HF drillpress - helps elinimates oopses from my shaky ahnds!
<21:08:18> "Joe N2CX": Weatheradio is the Canadian equivalent to the US NOAA radio - same freqs and SAME!
<21:14:08> "Bill - KD5TFD": spark fun stock went down by 4 in last 4 mins~
<21:14:45> "Bob - N2OJJ": I'M still waiting for xbee's in mail but soon...
<21:15:20> "John - NG0R (Mac)": George & Joe, nice show tonight
<21:18:20> "Bill - KD5TFD": A junior one
<21:25:16> "Bill - KD5TFD": http://www.google.com/url?sa=i&source=images&cd=&cad=rja&docid=lPMxefwepQD9lM&tbnid=EbGHAA_Wi14TOM:&ved=0CAgQjRwwAA&url=http%3A%2F%2Fwww.wharton.co.uk%2Fdigital_clocks%2F490_050.htm&ei=cDR3UfaHDKu62gWDuIDwDg&psig=AFQjCNGTL3Yc7PFbvHUHNtkMuwhZlXQK6w&ust=1366853104252987
<21:28:40> "Frank N3PUU": Bill, take a look at this link: http://doc.ntp.org/4.1.0/driver36.htm
<21:29:59> "Bill - KD5TFD": tnx for the link

Part 1: Remote 7-segment LED Display for the Precision Arduino Clock

This is installment of our ongoing Arduino project starts bringing together the various experimentation threads we've been doing so far: 

1) The basic Arduino Clock displaying time to an LCD;

2) Its synchronization with an accurate external source;

3) The Real-Time Clock chip (DS1307) and use of it to maintain time through power cycles of the platform;

4) Wireless communication between two Arduinos using the modular XBee radios; and

5) Display of the clock information to a 7-segment, 4-digit multiplexed LED module

So what we are focusing on this now is the start of our Ham Station Mesh Network in the form of a remotely located clock connected by RF link to the base station Arduino controller!



Experiment 3:  Radio Link for Remote Clock

In this experiment we again use a couple of "Series 1" XBee modules in default, out-of-the-box configuration to set up a remote clock display node using a 7-segment, 4-digit multiplexed LED display.  The base Arduino+RTCC+XBee sends the time code wirelessly to the remote node:  XBee+Arduino+Display


1) Base Arduino Node: Transmitter (shown on right) ...  clock_phase_2g_xbee.ino

2) Remote Display Node: Receiver (shown on left) ... Remote_Clock_v1a.ino


The Precision Arduino Clock operates the same as it has recently evolved to work in conjunction with the DS1307 Real-Time Clock chip to keep accurate time, even when the power goes down of course, and displays the date and time to the LCD display on this "base station", as shown on the white breadboard in the photo below.

However this time we are starting to use a new 7-segment, 4-digit, multiplexed LED module from Adafruit Technologies.  This display is controlled by a set of i2c control lines coming from a second Arduino sitting on the plugboard situated on the left side of the photo.  This "remote" Arduino is connected wirelessly to the Base Arduino by using those little XBee radio nodes we used last time in establishing a link between two "terminals" for bidirectional textual communication, as well as between a remote node measuring temperature and the base node displaying that temperature.

So this time we are using the same "transparent" protocol for the two nodes to be sending raw data between them, but we are only using one-way communication from the Base node to the Remote node, and we're sending the time digits!

The Base Arduino timekeeping sketch has some extra lines of code added to "send time to remote node", and the Remote node sits there waiting for the incoming time codes (happening every second), and it then displays those time digits to the 7-segment display!


Project Resources

Shield Schematics -- see below

Phase 0/1 Sketch -- Software for basic clock with manual register count-up (for software training purposes) and sync with tone decoder via CHU signal. Also handles external sync input.

Phase 2b Sketch -- Software now uses the RTC chip for date/time retention and timing. Current time set from computer when you first load the sketch onto the Arduino ... no more need for cumbersome serial console and "user time setting" menus!! Also no longer depend on "wait 1000ms" for timing ... we now let the RTC chip do it and we look for the transition of its output pin, clocking at 1 Hz interval. LED added to show RTC heartbeat. Software greatly simplified. Needs the RTClib (see next item).

Phase 2c Sketch -- Software that includes (and depends on) the RTC

Base Station Temperature Display Sketch ... Software for Base station to display temperature from Remote node

Phase 2g Sketch ... Software for Base Arduino node sending time data to Remote node for display

Remote Time Display Node Sketch ... Software for the Remote node displaying the time on the 7-segment LED

RTClib library... unzip, rename folder to RTClib and place into your Arduino libraries folder.

DS1307 Data Sheet (RTC chip)

LMC567 Data Sheet (Tone Decoder)

Arduino UNO R3 Information Page

Rookey Tone Decoder Board  

7-segment, 4-digit, multiplexed LED array





1) Mesh networks ... http://en.wikipedia.org/wiki/Mesh_networking

2) Point-to-point protocol ... http://en.wikipedia.org/wiki/Point-to-point_protocol

3) Overview of XBee ...  http://www.ladyada.net/make/xbee/

4) Which XBee module to use? ... http://www.ladyada.net/make/xbee/modules.html

5) Manufacturer of XBee Modules ...  Digi.com ... http://www.digi.com/products/wireless-wired-embedded-solutions/zigbee-rf-modules/

6) Passing discrete signals (pin hi/lo) from module to module ... http://www.ladyada.net/make/xbee/ref.html

7) Other Arduino XBee project pages:

8) XBee Manual ... https://dl.dropbox.com/u/43021514/CWTD/xbee_1/XB_802.15.4%20Manual.pdf

Part 2: Favorite Homebrewing Tools & Suppliers


Here's a list of essential tools for the homebrewer's workbench ...

1. Pad cutter crude “Island Pad Cutter”


    Harbor Freight  Item# 95343 “3/8" Double Sided Rotary Spot Weld Cutter” ... <http://www.harborfreight.com/3-8-eighth-inch-double-sided-rotary-spot-weld-cutter-95343.html>


    Smaller one can be selected from the Harbor Freight Item#1637 “7 Piece Brad Point Wood Bit Set” ... http://www.harborfreight.com/7-piece-brad-point-wood-bit-set-1637.html


    YouTube video on using brad point bits for this: ... <http://www.youtube.com/watch?v=uFLdDTT5-wk>

2. Cheap good enough DMM - Harbor Freight Item # 98025: ... <


    Good enough for casual use, often on sale for as little as $2.99.


3.  Cheap good enough drill press - Harbor Freight item # 60238 ... http://www.harborfreight.com/speed-bench-drill-press-60238.html


    N2APB and N2CX have used them continuously for over 5 yrs.


4. Hand punch (Manhattan pads, mint tin holes) - Northern Tools Item # 14572 ...  http://www.northerntool.com/shop/tools/product_16698_16698


    Harbor Freight sometimes a similar one in stock


4a.   8” Bench Top Shear/Brake Harbor Freight Item # 90757 ... http://www.harborfreight.com/8-inch-bench-top-shear-brake-90757.html


    Good for cutting and bending light sheet metal.  Also very good for cutting PC board material.  Used

    for cutting pc board stock for 100's of NJQRP/AMQRP kits.


    Freight charges are not trivial and the delivery guy grumbles when he makes delivery.



5. Drill bits and step drill bits. 


    Harbor Freight and Northern Tools items with Vanadium coating are economical.  Drilling PC board stock dulls them quickly.



6. Infrared Thermometer with Laser Targeting, Non-Contact – Harbor Freight Item # 69465 ... http://www.harborfreight.com/infrared-thermometer-with-laser-targeting-non-contact-69465.html


    Often on sale for as little as $29.95.  Good for checking component and heat sink temperature.


7.  3" Mini Tool Grinder/Polisher Harbor Freight Item # 94071  ... http://www.harborfreight.com/3-inch-mini-tool-grinder-polisher-94071.html


    Good for grinding and polishing small DIY parts and pieces.


8.  4" Mighty-Mite Table Saw Harbor Freight Item # 93211  ...  http://www.harborfreight.com/4-inch-mighty-mite-table-saw-93211.html


    Best for precision cutting small metal, plastic and wood.  Great for trimming connectors and IC

    sockets.  Comes with diamond blade but not recommended for pc board stock.


9. Stanley Snip, Straight, 12 In Stanley Item no DWHT70287. Available at Grainger and other industrial suppliers ...  http://www.grainger.com/Grainger/STANLEY-Tin-Snip-24A439


Good tin snips for cutting sheet metal and pc board stock.  Do not use a lesser quality snip.  N2CX has used the same similar pair for over 30 years!


10. Good quality flush cutter, needle nose pliers, nick-free wire strippers –


    Microcenter has a good selection of these as do Digikey and Mouser.  Stuff from Radio Shack and Harbor Freight or other knockoffs will dull and get sloppy very soon.  Quality matters in these commonly used hand tools.


11.  Automatic Center Punch with Brass Handle Harbor Freight Item # 621 ...  


    Good for precisely marking where holes are to be drilled.

12.  Dremel tool - AC or rechargeable - any good hardware store or hardware megastore

13.  50W Ungar soldering iron (Manhattan construction) - Lowes or Home Depot


14. "X Tronic 4000 Series" Model 4040 XTS Hot Air Rework Soldering Iron Station Kit

The name says it all.  At over $100 it's in a different class than the usual soldering iron but indispensable for high quality surface mount work.




Part 3: Cool Product of the Month ... Si4707 Weather Band and SAME Data Receiver



The Si4707 Weather Band and SAME Data Receiver is ...

The Si4707 IC is the industry's first weather band (WB) radio receiver to include a specific area message encoding (SAME) processor.

The Si4707 is a feature-rich solution including 1050 Hz tone detection, automatic frequency control, dynamic channel bandwidth filters, and digital tuning. In addition, the Si4707 provides a programmable reference clock and supports an I2C compatible 2-wire control interface, SPI, and a Si4700/01 backwards compatible 3-wire control interface.

The Si4707 incorporates a digital processor to provide SAME data, advance error correction, and SAME data quality metrics. Using this feature, the Si4707 enables broadcast alert data such as severe thunderstorm warning or flash flood watch to be displayed to the user.

Available in a tiny 3 mm x 3 mm QFN package, it eliminates the need for a front-end tuner IC, external ADC, DSP, RAM and numerous discrete components found in traditional SAME weather band radios.


- Weather band support (162.4–162.55 MHz)
- SAME processor
- 1050 Hz alert tone detection
- Frequency synthesizer with integrated VCO
- WB digital tuning
- Programmable reference clock
- 2.7 to 5.5 V supply voltage

Weather Radio Background:

NOAA Weather Radio All Hazards is a network of radio stations broadcasting continuous weather information directly from a nearby National Weather Service (NWS) office.

NOAA Weather Radio broadcasts National Weather Service warnings, watches, forecasts and other hazard information 24 hours a day. It also broadcasts alerts of non-weather emergencies such as national security, natural, environmental, and public safety (see: AMBER Alert) through the Federal Communications Commission's (FCC) Emergency Alert System.

The United States, Canada and Bermuda operate their government weather radio stations on the same band using these frequencies:

162.400 MHz
162.425 MHz
162.450 MHz
162.475 MHz
162.500 MHz
162.525 MHz
162.550 MHz

All stations transmit a 1050 Hz tone immediately before issuing a watch or warning, and this serves to activate the alert feature on many older radios. Except for Bermuda, all U.S. and Canadian stations transmit WRSAME codes a few seconds before the 1050 Hz tone that allow more advanced receivers to only listen for certain warnings that carry a specific code for the local area.


Specific Area Message Encoding, or SAME is the protocol used to encode the Emergency Alert System (EAS) and NOAA Weather Radio's SAME Public Warning System in the U.S. and Weatheradio Canada in Canada.

SAME data is transmitted as an AFSK Data Burst, with each individual bit lasting 1920 Ás (1.92 ms) each, giving a bit rate of 5205/6 bits per second.

[sound file: Same.ogg]

The entire SAME specification can be found at: http://www.nws.noaa.gov/directives/sym/pd01017012curr.pdf

Si4707 Weather Band Receiver Breakout Board

The QFN package is rather difficult to solder without reflow equipment. Sparkfun Electronics has created a "breakout board" containing the Si4707 and required support components. This breakout board is designed to run a 3.3 volts and brings the following signals out on 0.1" pin headers:

- 3.3V Power & Ground
- Antenna & Antenna Ground
- Audio & Audio Ground
- Si4707 Control Signals:

The breakout board sells for $29.95 and is available at https://www.sparkfun.com/products/11129

Sparkfun has produced example Arduino code for controlling the Si4707 which is available on github: https://github.com/sparkfun/Si4707_Breakout



Weather Radio General Information:


SAME Data Specification:


Si4707 General Information:


Si4707 Data Sheet:


Si4707 Programming Guide:


Sparkfun Breakout Board:


Sparkfun Example Arduino Code:


Sparkfun Breakout Board Schematic:


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