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'My Morse Guide', an AVR Electronics Kit Project
My Morse Guide is an electronics kit aimed at young people. The kit delivers both some fun in soldering the kit together as well as having a kit for playing with Morse code. My Morse Guide is a project by Ivo PA1IVO, Leo PA0LEZ and Marianne, and is a successor to the successful Share Your Morse project for the Jamboree On the Air 2013 at Scouting Elfregi Zaanstreek. This page contains a technical description of the project.
Er is ook een pagina met algemene informatie in Nederlands aanwezig.
The My Morse Guide electronics kit delivers the following functionality after it is successfully soldered together.
With the 'Key' key it is possible to send Morse code yourself with the kit, or an external Morse key can be connected via the PCB terminal block (short-circuit for key down).
- With the 'Mijn Morse' key the (pre-programmed) name of the owner is sent in Morse code, or the radio call sign in case of a radio amateur.
- With the 'ABC...789...Zulu' key the all characters, numbers and NATO alphabet words are send in Morse code, one at a time.
- With the 'Woorden' key the (pre-programmed) secret words are sent in Morse code, one at a time.
- With the '(Speaker/LED)' key the speaker and LED can be switched on and off for sending Morse code.
- With the '(Toonhoogte)' key the pitch of the Morse tone can be set.
- With the '(Snelheid)' key the speed ('WPM') of the Morse code can be set.
The schematic of the electronics is displayed below.
Table 1: Component list.
The heart of the logic of this kit is based on a small AVR microprocessor. The selection for a chip in the AVR range is only based on previous experiences with AVRs, and therefore the availability of software, programmers, and knowledge. A PIC microprocessor should probably also be able to do the job.
The AVR selection was based on the following criteria:
By using the AVR Compare Devices page (well done!) we selected the ATtiny85V, which has only 8-pins in a DIL housing, a supply voltage down to 1.8 Volt, and the maximum memory in this range.
- Low price
- Dual in-line package, so easy to solder for small childeren
- Low voltage, minimum 1.8 Volt was preferred over 2.7 Volt, as we are using two AAA batteries
- Maximum memory taken the criteria above into account
We looked for a small speaker, being a speaker and not a piezo buzzer. With a real speaker you are able to change the tone frequency, which is not possible with a piezo.
The speaker selection was based on the following criteria:
It is hard to find small PCB mounted speakers that are not piezos. We found one at Farnell (it's really a speaker, we opened one ....). It clearly peaks in volume at the resonance frequency of 2048 Hz, but it is still usable a few hundred Hz above and below the resonance frequency.
- Low price
- Easy to mount on a PCB by just soldering
- Availability on the semi long run (in case more kits have to be produced)
- Reasonable sound production, both in volume and in tone clearness.
The AVR software was developed with Atmel Studio, and therefore written in the C programming language.
All (electronic) components to build one kit.
Front and back side of the printed circuit board (PCB).
Connection for an external morse key and the empty battery holder.
A My Morse Guide badge connected to a real morse key
Research and development for the My Morse Guide project.
An AVR Dragon programmer is used to perform high voltage serial programming (HVSP) to the AVR.
HVSP is required to be able to use the reset pin of the AVR as an extra input.
Zero-insertion-force (ZIF) connector together with the AVR Dragon in an enclosure.
Extra connection to the PCB for easy testing.
© 2014-2017 by Ivo Klinkert, PA1IVO - Contact