PICAXE ELECTRONIC KEYER SHIELD
AN ELECTRONIC KEYER SHIELD FOR THE PICAXE AXE401 SHIELD BASE
PEKS Shield BASIC Code PEKS Bill of Material PEKS Schematic
Are you currently experimenting with the PICAXE AXE-401 development shield base? Have you had your fun with it? Have you boxed it back up? Not sure what to do with it? Why not make a simple yet small Morse Code electronic keyer!
The Keyer Shield Base
The PICAXE™ AXE-401 development kit with the PICAXE-28X2 chip is available from Altronics here in Australia for less then 20 dollars. It's an Arduino compatible shield base with the ability to except many different types of shield boards like Ethernet, MP3, stepper motor controller, motor PWM, LCD, GPS, GMS etc. etc.
Searching And Searching
Not wanting to reinvent the wheel, I searched and searched the internet. After numerous searches, not one electronic keyer shield project could be found. So, it was off to the back yard shed to make one.
The Prototype Shield Board
The prototype keyer shield artwork was painfully made with MS Paint. This can be exhausting on the brain as you have to continuously remember trace width, pad size, component pin out dimensions, scaling, mirror image etc. etc. It definitely keeps the mind active. Laser printing to high gloss photo paper, transferring the image to prepared copper with a cheap laminator and etching with Ammonium Persulphate was the technique used. The main problem with the prototype keyer shield is the header pins need to solder to the top of the keyer shield board while all the other components solder to the bottom of the board. This requires a double sided circuit board which I can not produce in the shed. Hence the reason the .BMP art work was sent out to be professionally made.
The Finished Shield Board
If you decide to build this project, remember the header pins solder to the component side of the board. Connections to the shield board are all made with screw type edge connectors. The RELAY terminal is a normally open contact from the reed relay. A reed relay was used do to its speed of operation and quietness. I have used other small relays in past keyer projects and they tend to sound like telegraph sounders. The KEY terminal is for an iambic paddle key. The centre screw of this terminal is the common. The BUTTON terminal is for a momentary, normally open push button of your choice. The SPEAKER terminal is for the connection of a small 2 inch speaker for side tone. The LED terminal is for a 5mm LED and the colour is your choice.
First of all, I would like to point out that I am not a programmer by profession or as a hobbyist. I definitely burned the midnight oil on a few occasions. In the end, I simply toyed around with the code until I got it to do what I wanted.
Assuming you're knowledgeable with the PICAXE development shield base, apply power and down load the BASIC code into the PICAXE-28X2 chip with the free PICAXE software.
The BASIC code is found above. Just cut and paste it into the PICAXE BASIC text editor.
When ever power is applied, the code will immediately start to execute. Upon power up, you will have 3 blinks of the LED or about 2 seconds to determine what the keyer does. If you do nothing upon power up, it will always be an iambic mode B keyer. I personally hate mode B but it seems to be the flavour of the day.
Upon power up...
1] Do nothing for two seconds = Iambic Mode B
2] Hold the Dot paddle closed = Iambic Mode B Auto Spacing
3] Hold the Dash paddle closed = Iambic Mode A
4] Hold both paddles close = Iambic Mode A Auto Spacing
Practice Modes: (in groups of 5)
5] Push button closed = letters
6] Push button, Dot paddle closed = simple punctuation [ , . / ? @ ]
7] Push button, Dash paddle closed = numbers
8] Push button, both paddles closed = letters, punctuation, numbers
A Word About Auto Character Spacing
This is an interesting topic. I believe Auto Spacing or Auto Character Spacing being one in the same may have started with some of the old logic gate Accu-Keyers of the early 1970's or maybe even the single IC Curtis keyer chips from back in the day. Regardless, AS or ACS is a technique by the electronic keyer, "when required", to add two extra dit length spaces, in addition to the mandatory single inter element dit space, for a total of 3 dit spaces. These three dit spaces are the correct spacing between the end of one character and the beginning of the next character. This forced 3 dit space stops the operator from sending strings of characters together.
Those expert CW operators who use a keyer with ACS enabled would not notice anything unusual. When I tried ACS for the first time I was totally disturbed by it. This was actually my electronic keyer trying to tell me I was not keeping good timing while sending. Over time and with practice, it has helped me not to run characters together and send more proficient code.
How to exit the modes
If you're in a CW practice mode, just squeeze both key paddles and the code will return to the 8 menus. If you're in a keyer mode, momentarily press the push button and the code will return to the 8 menus. If you press the pushbutton for more then about 2 seconds, this will send the CQ CQ message. The default is CQ CQ VK6HV, so remember to change my call sign to your call sign in the BASIC code before downloading to the PICAXE chip.
The PICAXE-28X2 chip has 4 memory slots, slot 0 - slot 3. Each slot has 4096 bytes available. In this project the BASIC code only uses 1,030 bytes of slot 0. This means there is a huge amount of code space unused for project improvement. Feel free to make changes and improvements.
1] If you're going to experiment with this project, then solder the Jaycar 10K PCB mounted potentiometers onto the PEKS shield board. If you are going to mount the PICAXE shield base and PEKS shield board into a chassis, do not use the Jaycar 10K pots. Use panel mounted 10K potentiometers of your choice and wire up the pots to the green edge connectors.
2] In Morse practice modes, it is probably better to let the keyer key your rig with the side tone on and the break-in off as your radio sidetone audio quality is better then the PICAXE speaker audio.
3] The PICAXE software can be found here: http://www.picaxe.com/
4] If you have dots and dashes on the wrong paddles, just swap the other 2 key wires.
The finished PEKS PICAXE Electronic Keyer Shield together with the PICAXE AXE401 shield base.
The PICAXE AXE401 shield base, the commercially made PEKS Electronic Keyer Shield board and the homebrew prototype PEKS Electronic Keyer Shield board.
The commercially made double sided PEKS , PICAXE Electronic Keyer Shield board.
The homebrew PEKS, PICAXE Electronic Keyer Shield board.