This project is finally finished and was the subject of an article in the Spring 2001 Iowa QRP Journal. The keyer is based on an inexpensive PIC chip and a keyer program that is available on the web. Construction details are presented so that the keyer can be duplicated if desired. The finished product is housed in an off the shelf enclosure that is roughly 2.5" x 1.5" x 1" in size. It has an internal battery and sidetone speaker. Assembly is very simple because the board mounts on internal standoffs and is held in place by the screws that hold the two halves of the enclosure together. The paddle and keyer output connect via board mounted 3.5mm phone jacks, eliminating the need for interconnecting wiring.
This keyer has been the primary keyer at my station since December 2000. I am very happy with the way it operates. It is small, lightweight, and has all the features I need for day to day operation. The standard memories make calling CQ painless and the user programmable memory works great for sending a contest exchange. Because the keyer is always powered by the coin cell, memories and setup parameters are retained when the keyer is not in use.
Keyer Design
This keyer is based on the K1EL design. K1EL offers several keyer kits, pre-programmed PIC chips, and a variety of other interesting products. You can check out the offerings at his web site: http://members.aol.com/k1el/. To encourage homebrewers, K1EL was nice enough to put the source code for his K8 keyer in the public domain. I programmed a PIC chip with the K8 code but one could also buy a chip from K1EL that has been pre-programmed with the K9 code. The K9 features a faster way to change code speed and a few other options. Both the K8 and K9 have many nice features. The K8 for example has three standard messages built in and two that can be user programmed. It accommodates Iambic mode A and B, can automatically insert appropriate inter letter spacing, has a tune mode, straight key mode, practice mode, and much more. I modified the K8 code slightly to allow another method of code speed adjustment. To learn more about the features of these keyers go to the K1EL web site and download the appropriate manual. I think you will be surprised at the features available in these keyers and the quality of the documentation that K1EL provides.
Below is the schematic of the keyer. The battery is a common CR2032 coin cell and the board is designed to accommodate a battery holder for this part. The CR2032 is rated at 220 mAh. When the PIC chip in not responding to a paddle or pushbutton input, it is in the sleep mode consuming 1uA. When the circuit is active it consumes about 5ma. The battery should therefore provide many hours of active operation and many years of standby operation.
P1 is the connection for the push button switch. Q1 provides keying for the positive keying voltages associated with most modern transmitters. The paddle should be wired to pull the Dit and Dah inputs to ground. The resistors and capacitors on these lines provide the PIC chip with some measure of protection against electrostatic discharge.
PIC Keyer Schematic
Construction Details
The links below provide additional construction information including a PCB layout, parts placement guide, parts list, enclosure drawing, and building instructions.
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