2016-11-13: RED LIGHT SHELF

If most astronomy stuff took place in the daytime I wouldn't need this, but it's dark out there at night, and I like to be able to see what I just tripped over. You always do that, right?...look back at what you just tripped over? Running around in the dark with a flashlight is OK, but sometimes two hands come in handy when you are fumbling around with a lot of parts. It's also nice to sometimes have an 'area of light', instead of a concentrated beam. I don't really like head lamps. They can cast a lot of light toward other astronomers, they attract bugs to your face, and with the way I turn the flashlight on and off several times a minute they just aren't practical for me.

The other thing I'm always in short supply of is a place to put things. Then it hit me -- a lighted shelf!

I ended up with the idea to use the same material for the shelf as those white plastic cutting boards. They are made of high density polyethylene. I wasn't sure how good it would be with light, but it seemed like it would be sturdy enough, and I hardly ever chop vegatables while using my telescope, so no conflict there. I ordered a piece 8x10" and 3/4" thick from TAP Plastics. They are stores on the US west coast you can just walk into and have pieces of plastic cut to order. Cool idea. Kinda like Kinkos for plastic. I had to mail order mine. I started to have visions of the plastic glowing a nice red color.



After looking through a lot of options on SuperBrightLEDs.com I ordered two. Sooo...the first one wasn't quite what I had in mind. Nice if you need to signal airplanes, though. The second choice was six loose LEDs connected in series. Much better. These LEDs had a max current of 50mA and six of them drew 40mA at about 13.5V. The battery voltage of my telescope stuff should normally be less than that. At the other end the battery voltage could be around 12V. Will that be bright enough?

The game plan was pretty simple. Drill six 1/4" diameter holes a little deeper than the LEDs and then connect them with a 1/4" wide trench for the wiring. Used a drill, duh, and then my favorite tool, my compact router. I'm lousey at drilling and routering, but it turned out OK. I just need to slow down sometimes.

Since the LEDs were wired in series there was one wire that just had to run to the last LED, and the other which had to stop at each LED. I'm glad there were only six. It was all a bit tedious, because everything had to be just the right length. I covered up my soldering mistakes...I mean the bare LED leads with shrink tubing.

The shelf needed a lip to keep things from rolling off. With the wires tucked into the trough I took some scrap redwood and made a facing for three of the sides. I predrilled everything before putting in the LEDs, so all I had to do after the soldering was move the wires out of the way of the screws and put things together.

   

Before finishing everything I gave it a whirl. Not bad. The HDPE may be a little too dense. It looked a bit better in person than it does in these pictures, but the plastic didn't quite glow the way it did in my dreams. Still, not bad.

Once the LEDs were wired up I drilled a hole in from the trough, another hole up from the bottom to intersect it, then I fished the two wires through. All of the wiring is hidden, except where it pops out of this hole.

Spiffy, huh? I left the loop of extra wire for the LEDs in case it was ever needed. The power cord is terminated with a 4-pin Amphenol connector that I use on my power box. I just used some 18-gauge red and black speaker wire for the power cord.

While I was deciding on the number of LEDs, and got an idea of how bright the different voltages were going to be, I kinda thought I'd get a voltage supply that would always pump up the voltage to 13.5V, and then lower the voltage and/or current to the LEDs from there to make them dimmer. Once I tested things a bit further I decided that 12V would make the LEDs bright enough. That simplified things. The battery voltage should normally always be above 12V, so they will always be brighter than 'bright enough'. I bought the dimmer box in the picture when I bought the LEDs. I decided to just use it. It controls the voltage from whatever the input voltage is down to about 8V. The physical and electrical size is overkill, but this is just a prototype, so it's OK.

At a dimmer setting I suspect will be bright enough for when I'm in cruise mode and not needing a bunch of light I measured the LEDs drawing less than 6mA. Of course, the lights will be off 99% of the time. These are "super bright" LEDs and they really do get bright quickly with a small amount of current when I compared them with some regular LEDs that I had.

So now the fun and games were over. It was time to figure out how to attach this thing to the tripod. I envisioned this being the worse part. I'll be opening a fortune telling business next week. It should do well. It's not the fact that I didn't have any idea what I was doing, or the part where I wasn't sure that I could come up with something. It was the part where I knew that no matter what I did there was going to have to be a 5-1/2" long hole drilled through something that had to line up with the two holes in the ear posts. I can't drill a straight hole of any length even with a straight bit.

I replaced the 3/8" round-headed bolt that is between the ear tabs for holding the tube on top of the tripod legs with a cap bolt. That made it stick out more. At this point I wasn't quite sure why I did that. That bolt was going to be involved, but there were a lot of rumors from the voices in my head about how. The right idea would come to me as I stood in the hardware store a few days later.

I started with a section of leftover redwood 2x4" that had been cut down to a 2x3". 1-1/2" x 2-13/16" to be exact for no particular reason. I used my scroll saw and generally cut the one side to the size and shape of the area between the two ear posts with the curved corners. You'll notice there are no close up pictures of that step.

The block was attached to the shelf with three fine brass-plated screws countersunk into the top. I may switch to stainless steel for the production version. I'm always afraid these cheap brass-plated things will snap off. I've had that happen before.

To keep from having to drill one long 5-1/2" hole I cut a dip in the side of the block facing the mount so I would only have to drill two shorter holes. Now the probability was double of drilling incorrectly. Notice how the hole that the long bolt (1/4"-20 6") is going into is a little misshapen? See what I mean? After a bit of scraping and twisting the drill bit it all worked out in the end.

So while I was standing in the hardware store (I told you this was going to happen) I figured out that by adding a smaller block of wood to the one with the long bolt, and running a shorter (1/4"-20 3") threaded bolt through it perpendicular to the long bolt I could screw the short bolt toward the mount which would tilt the shelf up and exert pressure on the whole assembly to keep the shelf from wobbling around. It would just tighten up everything. And what better place for the shorter bolt to land than...



...the cap bolt that I had no idea what to do with! You mate the shelf to the tripod with the long bolt, then adjust the tension of the whole thing by screwing the short bolt into the head of the cap bolt. The cap bolt takes a 5/16" hex wrench, so the short bolt's 1/4" diameter fits in the hole and doesn't wobble around very much. Nice! Since all of the pressure on this bolt was going to be in one direction I just pounded a T-nut into a 5/16" hole in the block of wood for threading. The head of the short bolt sticks out on the other side of the block and acts as a knob. It all just has to be finger tight. The shelf naturally droops a little when you put it on, so this tension adjusting bolt solved a bunch of problems. Even nicer!

This was a nice find. There wasn't going to be very much room between the end of the long bolt and the bottom of the shelf, and I really didn't want to hold the long bolt in place with a regular nut -- that would involve tools. Wing nuts were too big. This 3/4" plastic ball/knob with a 1/4"-20 metal insert is a little slippery, but it works perfectly. The 6" bolt was just the right length...for a change. I didn't have to cut it off or anything. Only the last inch or so is threaded, so it's not always chewing things up. I just added a brass washer to each end to keep from scratching the ear tabs.



That's all there is to it! You might notice that the width of the lip around the edges in the finished version is less than it was earlier. I just used some pieces that I had laying around that were 1/2" wide. That was too wide. Despite the fact that atoms are mostly empty space the lip pieces of wood next to the mount and the two silver knobs that hold the Losmandy 12" extension tube on to the tipod tube still couldn't occupy the same space at the same time. I redid everything with 1/4" thick pieces of wood. That fixed everything, and it made it look a little better too.

   

A couple action shots during construction. This 8x10" size shelf on a Losmandy GM-8 with the 12" extension stays out of the way of the counter weight shaft down to a mount latitude adjustment of about 12 degrees with it mounted on the northeast side of the mount. That's the side where my mount controller box has settled. I point the leg with "Losmandy" on it to the north when I set up.

For times that I don't want the red light shining up I made a mat that fits inside the lip out of two pieces of laminating paper with a layer of aluminum foil between them. This will keep the light out of your eyes, and the shiny side makes the light below the shelf a little brighter than without the mat.

After I see how this version of the shelf performs I'll get on making the REAL version. I've already started a list. It will be the same idea, but new and improved and prettier. It's gotta be prettier. There's not a lot of opportunity to make it shinier.

THE END

UPDATE:

So I finally got around to redoing the shelf with the 1/2" piece of cutting board material and the solid piece of wood for the mounting blocks after the first of the year, however, I got to step 1 -- removing the wood mounting blocks -- and decided the original shelf was good enough for now. I did take a 1/4" roundover router bit to the wood blocks to make them look a little better, and some sandpaper to the wood sides around the edges to fix up a couple errors. I may go back after it with a 1/2" roundover bit. More has to make it better. I'll get some run time on it and see if I need to make the new version.

2018-09-04