D-Cell Battery Pack With Integrated Keyer Paddle
Concept
I wanted to build an emergency power supply for the FT-817 that is
portable, low-maintenance, and low-cost.
Alkaline cells have a good shelf life, so they can be stored in bulk, eliminating
the need for trickle charging or other types of maintenance. This project is very simple and can be built
in just a few hours.
Materials
The PacTec (http://www.pactecenclosures.com/)
LH68-175 plastic enclosure seemed like the ideal size to house 8-10 D-cells,
but it needed some minor modification.
The bottom pylons meant to hold a PC board need to be lowered to allow
room for the D-cells. The top pylons
need to be removed altogether. Getting
the D-cells in is a snug fit, but the next larger-sized enclosure is bigger
than I wanted to work with. I
originally was planning on 10 D-cells and a separate keyer paddle unit. 10 fresh D-cells will have a slightly higher
voltage (16.1 V) than the FT-817 allows and I was uncomfortable with that. Removing one D-cell gives a fresh-battery
voltage of about 14.4 V and made room for the keyer paddle.
The base and pivot point top are cut from .025 aluminum sheet.
After having some bad experiences with plastic battery holders, I found
some aluminum D-cell battery holders that are nearly as inexpensive as plastic,
but more durable and withstand soldering on the lugs much better. I used model PH-BH65 from Action Electronics (http://www.action-electronics.com/index.htm). There are other models, including one that
holds two D-cells available from Mouser Electronics (http://www.mouser.com/). If I were doing it again, I would go with
Mouser.
I used surplus snap-action switches (also called “microswitches”) for
the keyer paddle. I found that the
Cherry Electronic Products E23 model was suitable. Detailed information is available at http://www.cherrycorp.com/english/switches/miniature/e21.htm. Mouser Electronics appears to have them
in-stock as well.
The actual paddle was cut from 3/4” by 1/8” aluminum stock. Being an old-time bug operator, I opted for
a single-paddle key, rather than a squeeze key. Either could be built, with the dual-paddle being just a little
more complex. The snap-action switches
don’t make for ideal keying action, but they simplify construction at low cost
and never need cleaning or adjusting. I
tried a couple prototypes of a dual-paddle (squeeze) key, but it seems to be
more difficult to get the right combination of force vs. travel on the paddle
using the snap-action switches. Not
being a squeeze-keyer, I’m probably not a good person to judge the results,
however.
Images (click on image for large view)
Alternate view for squeeze keyer paddle
Last updated: 4/14/2006