Power Box 12volt - 18volt - 110volt
for the LX200

       

by Jim Lowry <jim-lowryatt.net>
Other designs:

-----A ONE PARAGRAPH "ABSTRACT'-----

Designed to provide portable power for the amateur astronomer. One 12 volt battery provides 12 volt outlets for various accessories, 18 volts to power a Meade LX200, and 110 volt AC current to power an external clamp light with a 40 watt red bulb. This lamp comes in especially handy when leaving a dark site in the middle of the night!

-----THE ACTUAL "TEXT EXPLANATION"-----

During the last year, I got very tired of lugging various "pieces" to provide all of the necessary power for a typical viewing session. In addition to my main battery supply, I needed my Meade 12 to 18 volt converter for the LX200. But I also needed a pigtail clamp when using a dew remover or 12 volt hair drier. Then there was always the question if the battery held enough charge for the planned session.

With these problems in mind, I set about planning something which would hold everything in one convenient box - providing any and all voltages that I would need. I also decided that 110 AC current would be a great added benefit. Thus the idea for my "Power Box" was born.

EXTERNAL CONSTRUCTION
12 inch pine boards were cut to make a 12" by 12" by 12" box, with the sides actually being 15" to give clearance for dewy grass. I simply screwed them together as well as gluing, except for the top board, giving me easy access to the inside unscrewing only four screws. The wood was stained, and then triple coated with polyurethane to protect from moisture.

TOP PIECE
The top holds a one piece double switch, one acting as the main power switch, and the other to prevent accidental power discharge if the external carriage bolts somehow get connected by a conductor. There are also two plastic capped cigarette outlets - one for 12 volts and one for 18 volts. A standard radar detector coiled cord connects my telescope to the 18 volts. The other is available for using my dew protection system. On top are also two carriage bolts. These provide easy clamp on access to recharge the battery. The Radio Shack motion detector allows me to leave the telescope in the yard or on the porch to cool down, without worrying that "uninvited" guests get too close. Finally I have a strong handle mounted in the middle for easy carrying.

FRONT PIECE
The front holds the Radio Shack 0 to 15 volt meter, and a standard wall mounted 110 volt switch and double outlet. This is connected to the internal inverter, capable of providing 300 watt continuous power from the 12 volt battery. There is also a bank of three identical switches. One powers the meter, which is direct to the battery so that the master switch does not have to be on to check the power. A second switch activates the alarm, and the third is empty for possible future expansion. There are also three standard cigarette outlets for extra accessories.

OTHER PIECES
Both the left and right pieces have a 3 inch square hole cut out for ventilation purposes, covered with standard mesh screening. The 12 volt computer fan is mounted inside one of these blowing air out. This prevents any build up of heat from the inverter and various converters.

My 34 amp hour battery was bought at a hobby supply store for around $80. The electronic pieces cost around $50 from Radio Shack, and the 300 watt inverter was $69. I now have enough power for several nights of viewing without the dew protection system, and at least 10 hours of viewing using all dew accessories. Charging the next morning takes less than one hour with a standard automobile battery charger set to automatic.

Subject: Field Power Box 

From: Thomas Wideman <twidemanearthlink.net>

Thanks to Jim Lowry for the great field power supply design in the Topical Archive!

I had to tinker, so I built a slimmer model and have put info about it on my site at:

   <http://home.earthlink.net/~twideman/powerbox.html>
     Note: should open a new browser page over this one.

Subject: Battery Pack Design URL    

From: Pat Lanclos <SkySgtaol.com>

I have yet another submission for you to consider posting on the MAPUG archive. It is a webpage I have developed showing and describing a 12v battery system I made to power my telescope. Maybe some other MAPUGGERS will find it useful. The address is:
   <http://members.aol.com/planclos/index/battery.htm>
     Note: should open a new browser window over this one.

Subject: Battery Box Design  

From: Rob La Pointe <m81pacbell.net>

Hopefully, the images will speak for themselves or contact me.

Subject: LX200 18 Volt Power Source 

From: Ray Wallace <ray_wallacejuno.com>

One of the problems LX200 owners have is finding a reliable system that produces 18 volts DC to power their telescopes. The common solutions on the commercial market seem to be DC to DC converters for about $100 a piece that are overpriced and inadequate for the application. Another alternative is gel cell packs. They can suffer from inferior quality components and circuit design. After having a $100 DC to DC converter burn out, I made an 18-volt system that is both inexpensive and, electrically, as good or better than anything I've seen commercially available.

It uses 2 car batteries. One is in my car, the other one I bought at K-Mart for about $35. I bought 3 x10' long, light duty, extension cords for a few dollars a piece, and 3 sets of alligator clips made to connect to car battery terminals also at K-Mart. From an electronics store, but not Radio Shack, I bought an ECG970, a heat sink and a 1k ohm, 10 turn, pc mount potentiometer and a plastic box to put the regulator assembly in. The ECG970 is a positive variable voltage regulator. The potentiometer connects between the output and ground pins of the regulator and allows it's output to be varied between 2 and 35 volts.

Also, this particular regulator provides up to 3 amps output. Plenty of power for the telescope and any accessories. The 2 batteries are connected in series with one of the extension cords to produce 24 volts. The extension cord and alligator clips on one end of the regulator box should have their polarity marked (+-) for quick reference. The positive (+) clip is connected to the positive battery terminal that has 24 volts output. The negative (-) clip is connected to the extension cord coming from the negative (-) terminal of the battery. The lead on the other end of the regulator is connected to the telescope.

During the initial setup, I monitored the regulator output while I operated the telescope motors in fast slew. I adjusted for about 18.25 volts. Plenty of power for any motor operating scenario. As for pro's and con's: The con's are I switch the batteries every week or two using the car to keep the batteries fresh and charged. That's about a 5 minute job. The pro's: clean DC with plenty of power. No worries about burn out (the regulator or a motor or motherboard).

Subject: LX200: Field Power Solutions  

From: Larry Owens

I use a home brew power system, that actually fits into a computer bag. I setup the 10" LX200, set the power bag under the scope, pull out the 18v wire, plug in the dew heater (20w) and optionally the computer and I'm set. I use this system even when AC power is available, because since everything is in the bag, it's more trouble to find extension cords, set out the power supply and there are of course more things to trip over. I even have room in this bag for binocs and a flash light or 2, but it's pretty heavy.

The power system consists of a lawn tractor lead-acid battery and a 150w continuous (200w for 5min) power inverter from Radio Shack. Attached to the battery is a cigarette lighter type receptacle, wired directly to the battery with the + terminal of the battery covered with a plastic protector. I then have a "Y" adapter plugged into this to power my DC dew heater and to plug in my inverter. Into the inverter I plug the Meade 18v power supply (which I keep in the bag permanently - just pull out the wire) and the laptop when necessary.

To charge the system, I attached two 50w 4 ohm resistors in parallel for current limiting to a smaller DC receptacle. I plug my 15v laptop power supply into this and it charges the system nicely overnight. During charging the resistors get warm to the touch when the battery is low, and after a few hours the resistors are cold to the touch indicating no more current flow and a complete charge.

I've used this system for about 3 months so far, and have used it continuously for as long as 8 hours, with lots of slewing, dew heater on full 20w and a couple of hours of computer. Do not yet know how many hours I'll get out of this since I've never run the battery down.

I considered using a higher wattage inverter, but the 150 watter doesn't even get warm under the load. Since it will handle 200w for as long as 5 min, and since slewing is an intermittent high current activity, I think this is more than enough.

Cost: The inverter was $79, the battery was $39, I had the computer bag, and various connectors and components no more than $15. I also had a suitable charger which could be built for another $20 or $30. My investment: $133.

Subject: 12/18/120V Power Box Design URL

From: Danny Cobb <dndcobbbellsouth.net>

I have yet another 12/18/120V Power Box design, download a Acrobat PDF file by clicking here.