AmateurRadio.com

In a recent conversation with my good friend Lewis, we started discussing Morse code, training and the old equipment that was used to educate and teach the code to newcomers. In particular we discussed the old Datong D70 practice oscillators.  Lewis carried on the tell me that his Datong  like so many others started sending odd illegal characters and essentially rendered the kit useless. Of course you could whip of the lid and replace the logic chips, but I thought of recreating the Datong functionality in a new Arduino sketch.

So here is a breakdown of what the Datong offered:

1. Either Mixed, letter or number combinations
2. Groups of 5 characters
3. Variable speed ( up to 37.5 word per minute)
4. Variable character spacing (up to 4 seconds)

The Datong also allowed you to connect a telegraph key, and your headphones. But for now I will focus on the code generation element of the project.

The finished project has just a handful of components and can easily be created on a breadboard, or indeed if you have an old broken Datong you can reuse the box and panel to really replicate the old kit.   The complete project includes 3 variable resistors (1K LIN) for Character speed, gap and volume. It also needs a 3 way switch to select the mode.

The Arduino I’m using is the UNO. Arguably the most popular Arduino on the market, but I have also tried the sketch on a Nano and it works fine – just some customisation of pin assignments is all that is needed.

On start up the Arduino checks to see which switch is LOW – it also saves the current mode and checks if the saved mode is the same as the current selected switch. If this is different, then the Arduino has had a change in the mode selection and resets.

When generating the tones, the Arduino randomly selects a character from an array. With that chosen letter – it calls a function and plays the corresponding tone functions. 2 functions exist as a DIT and a DAH.

The rest of the functions are dedicated to allowing the speed and gap to alter and also displaying the results on the LCD panel (completely optional).

Here is a short video of the kit working, and a link to the source code.

In a recent conversation with my good friend Lewis, we started discussing Morse code, training and the old equipment that was used to educate and teach the code to newcomers. In particular we discussed the old Datong D70 practice oscillators.  Lewis carried on the tell me that his Datong  like so many others started sending odd illegal characters and essentially rendered the kit useless. Of course you could whip of the lid and replace the logic chips, but I thought of recreating the Datong functionality in a new Arduino sketch.

So here is a breakdown of what the Datong offered:

1. Either Mixed, letter or number combinations
2. Groups of 5 characters
3. Variable speed ( up to 37.5 word per minute)
4. Variable character spacing (up to 4 seconds)

The Datong also allowed you to connect a telegraph key, and your headphones. But for now I will focus on the code generation element of the project.

The finished project has just a handful of components and can easily be created on a breadboard, or indeed if you have an old broken Datong you can reuse the box and panel to really replicate the old kit.   The complete project includes 3 variable resistors (1K LIN) for Character speed, gap and volume. It also needs a 3 way switch to select the mode.

The Arduino I’m using is the UNO. Arguably the most popular Arduino on the market, but I have also tried the sketch on a Nano and it works fine – just some customisation of pin assignments is all that is needed.

On start up the Arduino checks to see which switch is LOW – it also saves the current mode and checks if the saved mode is the same as the current selected switch. If this is different, then the Arduino has had a change in the mode selection and resets.

When generating the tones, the Arduino randomly selects a character from an array. With that chosen letter – it calls a function and plays the corresponding tone functions. 2 functions exist as a DIT and a DAH.

The rest of the functions are dedicated to allowing the speed and gap to alter and also displaying the results on the LCD panel (completely optional).

Here is a short video of the kit working, and a link to the source code.

You are probably familiar with the Ground Fault Circuit Interrupter (GFCI), also called Ground Fault Interrupter (GFI), Residual-Current Device (RCD) and a few other names. While doing some electrical work for a family member, I discovered Arc Fault Circuit Interrupters (AFCIs) in the breaker box. Having a genuine Electrical Engineering degree (two, actually), I’d like to believe that I am reasonably up to date on basic house wiring. But somehow AFCIs had escaped my attention, even though they started appearing in the National Electric Code over 10 years ago.

A bit of searching on the internet revealed that these newfangled devices are intended to detect arc faults are below the trip level of a normal circuit breaker. Think in terms of a frayed extension cord that arcs over, creating a fire hazard, but not exceeding the 15 ampere rating of a typical house circuit. As usual, the Wikipedia entry is a good place to start. AFCIs detect arcs by monitoring the current behavior throughout the 60 Hz cycle. There are characteristics in the waveform that indicate an arc condition exists, causing the AFCI to disconnect the circuit. This article goes into more technical detail if you are interested:

New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)

Just like GFIs, AFCIs are available for installation in the main breaker panel and for installation at the electrical outlet. The diagram below shows the block diagram of a typical single-phase AFCI. This is not your old school circuit breaker but a complex system that performs both arc and ground fault detection. As already mentioned, the arc detection is performed by sensing the current behavior. The ground fault detection senses the difference between the current leaving and returning to the device. If there is a significant mismatch between the two currents, a ground fault has occurred.

From “New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)”

This post is just a quick introduction to AFCIs, with a USA perspective. Your local building codes are now or will soon be requiring AFCIs on new construction, so you’ll probably encounter them sooner or later. The National Electrical Manufacturers Association has a website with additional information: www.afcisafety.org.

73, Bob K0NR

The post Meet the Arc Fault Circuit Interrupter appeared first on The KØNR Radio Site.

This year at the RSGB convention we will be running a buildathon based upon the same format of the other successful build events in the past – this is an excellent time to attract a new audience to our events.

This year however we are using a new kit. The Acorn II kit developed by Kanga Products and M0XPD, is a Software Defined Radio kit that runs on the SSB portion of 40m. But the kit can also be configured to run on any HF band – assuming you have a Band pass filter & a suitable Local Oscillator. The kit has been developed to allow you to pipe in an external Local Oscillator and allow you to connect Band pass filters for other HF bands.

The kit was developed to run with the M0XPD Si5351A Arduino shield, which allows you to use the Arduino as a VFO. And can plug straight into the radio as a local oscillator

Using just a stereo line in on a sound card, and some widely available SDR software (Such as HDSDR), you can get great results from little financial outlay. It is indeed a great introduction into SDR.

I built one of the prototypes here is a video of the build. I will cover configuration & set up in a forthcoming video – perhaps when I have access to a good 40m antenna

This year at the RSGB convention we will be running a buildathon based upon the same format of the other successful build events in the past – this is an excellent time to attract a new audience to our events.

This year however we are using a new kit. The Acorn II kit developed by Kanga Products and M0XPD, is a Software Defined Radio kit that runs on the SSB portion of 40m. But the kit can also be configured to run on any HF band – assuming you have a Band pass filter & a suitable Local Oscillator. The kit has been developed to allow you to pipe in an external Local Oscillator and allow you to connect Band pass filters for other HF bands.

The kit was developed to run with the M0XPD Si5351A Arduino shield, which allows you to use the Arduino as a VFO. And can plug straight into the radio as a local oscillator

Using just a stereo line in on a sound card, and some widely available SDR software (Such as HDSDR), you can get great results from little financial outlay. It is indeed a great introduction into SDR.

I built one of the prototypes here is a video of the build. I will cover configuration & set up in a forthcoming video – perhaps when I have access to a good 40m antenna