Power box
Intro and planning

Contents
As this is quite a large project, I've decided to split this project into several pages. Each page dealing with a different aspect of the project.
Overview
This is perhaps my most ambitious project to date. Having been using my scope, it's amazing how I've still got the same problems that I had at day 1. Namely these problems are powering the scope, transporting the equipment and keeping everything simple to setup! I've changed my scopes equipment boxes several times, but always end up cramming stuff in. Toolboxes just don't do the job. I was constantly worried that my eyepiece might get damaged, and I even managed to scratch my Autostar (I call it a battle scar).
Also, there are problems with setting up the scope, as the effort required to plug in my dew heater mean's that most nights it's just sitting in the box, and not helping to stop the inevitable onset of Dew.

That's enough of the problems, now for the solution. I've just bought a new 85Ah Marine/Leisure battery; it's about the size of a 44Ah Car battery. And it weighs in at 23Kg's. Not light, but it's more than enough to supply power for my scope and all camping type needs for an entire weekend. I know it's kind overkill, but it's cheaper than a 24Ah Sealed Lead Acid battery. (About 1/2 the price, give or take). Besides, I'd rather have too much power than not enough.

I figured that this is OK for lugg-ability, as the finished unit will probably weight in at about the same my OTA or tripod. But I don't want it to be much more.

At the moment, I'm still working on the design of the box. Currently I'm in the process of getting the components together for what will be built into the unit. The idea is that I'll be able to pull one lead from the box, attach to the scope, and everything will be powered up in one foul swoop.

Another consideration that I've got is to try and help preserve the scope and increase its life. To that end, I'm going to make a power distribution box, that will attach to the scope, this will be used to supply power for the scope and dew heater, as well as take the strain from the weight of the wiring loom. (Currently the bulk of the weight is taken buy the scope's power connector, which is not a good thing)


Basic Design
This project will be sub divided into two parts, firstly there's the power box itself, then there will be the distribution box on the scope.

One thing that is not a concern for this project is saving power, there's 85Ah! To play with! 85Ah!!!!! Seriously though, There's still not excuse for wasting power needlessly, it's still worth considering the environment. And already I'm 1/2 thinking about a solar charger project which will power my scope forever, for free! I'm only half thinking about it as I want to be able to add this, and not design my box in a way that rules it out.

Power box contents
What's going into the power box?

This one of the most important questions for the project, if I get this right, it'll cut down the need for toolbox's alot. Currently I'm working on the devices that will built into the box, here's a list of the items that I want to build into the box.


Each of these devices is a seperate circuit in it's own right. Lets spend a little time talking about each of these. I'll skip the battery as you already know about that. (85Ah! Still can't get over it)

Dew Heater Controller
This is the controller from the Dew Heater project. If you like, you could call this the Mk2 Heater. Again it's based on the same design, I'm just implementing it in a slightly different way. The controller will be run directly from the battery, then a single pair of wires running out to the scope. (See the section on the distribution box for what' happens next) Also, I'm going currently researching a circuit that I can used to give a visual in the dark feedback on what setting the heater is currently on. (It'll be a variation on the Battery level meter)

Battery Level Meter
This is a simple circuit that will display a bar graph of the current battery condition, I'll know in plenty of time for when the battery will need recharging.

Fuse Board
I think a really nice touch would be to have a proper fuse board, this is a really simple circuit, and will help to finish the box properly.


Lighting
This is another important thing to think about, Instead of using torches for most of the work I'm thinking about making a Red light lighting circuit. As we all know, it's a real pain in to work with a torch all night, Afterall I'd need to hold the thing all night and it just plain gets in the way. I've tried a strap to attach it to my head, but it's just irritating as the thing never points where I want. My idea here is to make a few low power lights that can be turned on and off as desired. There will be one in the Power unit, lighting the control panel, and box itself. A little desk light, that can be used for looking at maps/books and stuff like that (probably won't get used much). Also another light on the scope itself, to illuminate eyepieces, and other stuff on the scope.

Others
I did think about putting in a little FM Radio, that would be a fun item, as it wouldn't pull alot of juice, and during a long lonley observing session would give me something to listen to. Also an illuminated clock, would be nice. These items I've decided are a little to much for the moment, but there will be room on the box to do this later.

After alot of thought, and an attempt at constructing a purpose built box, I found that it would weight too much. There would also be practical problems of fitting the electronics into the box. So for the time being, I've had to drop the idea of a purpose build box. Instead, I've opted to leave the battery loose, and fit a cable and plug, which connected into the project box.

Scope power distribution box
This box will be used for a couple of jobs. First, it'll provide a single point of contact from the power box, One plug and I'll be up and running. Second, take the physical strain from the weight of the cable. (better that than the scope) Third split the power on the dew heater so that I can plug in several heaters at a time. And finally, provide a place to plug in the Red Lights.

It's important that this box can do all of the above, whist still being as small as possible, if it's too big, it'll get in the way of other devices that attach to the scope. This is perhaps the simplest part of the project, and provided that I design it properly, it can be build and uted before the rest of the project is completed.
I'll need to build a custom lead, which accept power for the scope. That'll be enough to start with.

©Copyright 2005 Colin Dawson
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