Field Power Supply -- Addendum

Barry M. Batts of Corona, CA wrote to me after building a similar box.
His comments highlight a few things that both he and I learned while building these boxes.
I have posted copies of our correspondence so you can learn from our mistakes,
thought processes, and "learning experiences".

Barry wrote:

Hello Tom,

My Name is Barry M. Batts. I live in Corona, California and I own a 10 "LX200. Just wanted to drop you a line to let you know that I recently completed construction of a Field power supply using your plans as a general guideline. I am very satisfied as to the performance thus far, and am wondering if you are still using yours and how has it held up under use? I wanted to thank you for such a concise article (and plans) on how to build the unit, and to let you know that it was pretty easy to build following them. I added a few features of my own and thought you might like to hear about them:

1. I constructed my box out of 3/4" plywood for the top and bottom sides and 1/4" plywood for the for the front and back. The top piece (3/4") I used a router to cut down to 1/4" or so to mount the switches and meter.

2. On the top piece I installed hinges on the back so that I could open the box when needed and wouldn't have to install and any quick connectors to any wires. This made it easy to attach the wires to everything. Also the box is slightly bigger and wider so that I can pull the battery out very easily when I want to. I couldn't tell by your pictures, but I installed spacer blocks on the bottom inside to surround the battery and to keep it in place at the back bottom of the box.

3. With the box being slightly longer and wider, I was able to mount the 18v converter on the right upper side of the box (looking down into the box) instead of in the front. This gave me enough "slack" on the 18v output connector wire to run through the top panel of the box via a "compression cable fitting" . This type of fitting allows the connector to be pushed through the connector as a whole, then pulled back to secure with a screw cap which compresses a "cone shaped" rubber "O" ring which secures it in place. I did this because I didn't feel comfortable with too many cable connections inside the box that could come loose over time. Also, I found a plastic cover (I got it off of a tool bit at work) to cover the plug when not in use.

4. I opted for 2 handles on the ends of the box rather than 1 large handle on top. I just didn't feel comfortable with one handle for carry and was concerned that the weight may be too much for my wife or children to carry with 1 hand. ( when they actually help...ha..ha)

5. Did you have any problems with the paddle toggle switches for the fan. meter, and LX200 18v power? I did....After I soldered all my wires to the switches, the switch for the fan power stayed on all the time....I may have applied to much heat when I soldered it. Anyway, I ended up going with the regular type metal toggle switches for them.

6. I felt that I would need a cover on the outside front of the box to cover the 12v receptacles so I put a hinged piece of 1/4" plywood over these.

Well, that's About it and I hope it doesn't sound like I reengineered your design, I just thought you'd like to hear from someone that built one of these baby's. Take care and thanks again for the design, also any additional input you can provide on the unit will be appreciated and any other "designs" that you know of for the LX200 scopes would nice too!!!!

Barry

My reply:

Hi Barry,

Thank for writing; I'm glad the plans worked for you. It sounds like you were able to look at them and make changes that I probably should have made when designing mine! ;)

Making the sides thicker was good, so the side handles work. Much of the little woodwork I did was simply to provide a load path for the single handle on top; stronger sides takes care of that. I still like the thinner piece on top just to avoid the router work (I'm lazy ;) but that was my second option.

The hinged top is much better. I didn't realize that the Wal-Mart deep-cycle battery isn't a "maintenance-free" type (I fried the original one last year trying to charge it too quickly) and needs access for adding water, etc. My design requires about 10 screws to be removed to take off the top and get to the goods. My box is snug enough that the battery doesn't really move around, but adding any space around the battery would require spacers as you have done.

Moving the 18v adapter up and away from the battery as much as possible is probably a good idea. I don't know how corrosive the battery gases, etc. are but the insides of the box and the adapter are looking a little "dirty" -- not bad, but enough to make me wonder. The connectors haven't been a problem, but they were all used as a quick solution to how to be able to separate the parts.

I normally carry it one-handed, and still like that idea (I can still carry other stuff, hence less trips to and from the truck). However, load transmission (and kid's help) would definitely be easier with one on each side, in a thicker side as you used.

I originally had problems with the charging switch, and about 6 months ago I somehow broke a solder joint on the master switch, which I repaired using a "wind resistant" blue-flame type cigar lighter in the field. That repair was iffy (but it got me through the trip) so I replaced the switch when I got home to be safe. Putting enough heat on the terminals for the large wire that I used was pretty tough on them, and I definitely had a "learning experience" with the charging switch (which I replaced, of course). Actually, I didn't have any problem with the little switches you mentioned (fan, meter, 18v), but did with the charging switch and the master switch.

I have left the 12v outlets open and uncovered, and have had zero problems with them. I do occasionally wipe them out with a dust rag and WD-40, but they've been reliable uncovered.

Re-engineered my design? Heck, my box is just a re-engineering of Jim Lowry's design. That's the neat thing about this project, we all take a few ideas from each other and come up with what's best for our personal needs.

Mine's been reliable. I always take it with me, even if I know 110v will be available. If nothing else, I use it to run the air pump to inflate my air mattress when I'm camping. (Which brings up one design feature I'd like to add -- I have to swap the 5a fuse for a 20a to run the 12v air pump without blowing the fuse, I'd kind of like a switchable 5a-20a fusing arrangement -- is that too geeky? ;)

Best Regards,

Tom Wideman
Grapevine, TX
tom@wideman.org

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