Project: The Star Trek Room

[ChrisQ]

Hello, and thanks for any help you guys can give me on my project.

First a little background so you can see what I want to accomplish in the end. I tend to run on a bit so please skip the next couple paragraphs if you want to get right down to business.

For my midlife crisis I decided that I enjoy building models and in the last couple years have built a couple dozen star trek models. At some point I converted an extra bedroom into a home theater room where I can watch my shows while models are flying around the room. I painted the ceiling and 3 walls black, put some rope lighting up, and have been hanging them from the ceiling. It looks cool (ok it looks nerdy), but not cool enough.

As the centerpiece of the room I bought a humongous 1:350 Enterprise (I only hope mine turns out half as well as the one in the link) and decided it had to be lit. Then I realized the rest of them would look pretty crappy and decided to rebuild all the models again and light them all. Plus I need a lot more practice at modeling (and wiring) before tackling the big one.

I have bought a bunch of the models again, and a couple lighting kits so far, and am building the first of the lighted ships.
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Now, here is where I need some help planning. I have successfully modified an ATX power supply so that I can just wire up whatever I want it to power. This is where I got my only recent knowledge of electronics. I am using it to power some fans on a spray booth I just built and plan to mod 2 more for this project. One for my bench and one to power all the models.

Here is my plan:

I will be introducing each new model as it is built, meaning at first there will be one kit on the circuit and at the end there will be 10, 12, or more.

The kits each run between 6 and 9v. I have done a little reading and found that I can use either voltage regulators or just beef up my resistors to slow down the juice.
I also will be using an ATX PSU on my bench to test these models as I am building them so adding proper resistors or a voltage regulator to the kits will have to be first on the list.

My concerns:

1. After many ships are on the circuit, will the ship on the end of the line get enough power?

2. How do I properly reduce the current to each model?

3. Any other suggestions will be appreciated.

 

[(*steve*)]

1) if you need anything like 12V at 18 amps I will be very much surprised. For LED lighting I would be surprised if your total current draw exceeds 1A.

2) Check the sticky that describes how to use LEDs. There's no such thing as "reducing the current". You just have to make sure that everything is set up for 12V and the correct current will be drawn from the power supply.

3) Since your theatre is likely to be often in semi-darkness, I would probably design lighting to operate at low current from 5V and ensure that the current is still safe at 12V. Since you're using a PC power supply, you can switch from 5V (dim) to 12V (bright) depending on the ambient lighting conditions.

edit: The kits run on 6 to 9 volts? I assumed you would be designing the lighting yourself. (So much for following your recommendation to skip reading bits ) Are they just lights? Are they LEDs, or bulbs? What current do they draw?

 

[ChrisQ]

Thanks, Steve. I knew I was being lazy when I typed about reducing the current. Rather than trying to decrease the output of the PSU, I want to make sure the electronics can handle it. I will check out the sticky tomorrow night. I still don't quite have a grasp of it.

As for switching to 5V, I wish I had thought of that before spending an hour making that stupid picture. I could probably wire the room for 5V and call it a day. It'll always be dark in there, and I don't want the light from all those models brightening the room too much anyhow. All the different lighting kits are rated for 6V or higher so as long as the leds will still light up at 5V I can just install them without changing anything.

I will build the first model, hook it up to 5V and see if it's acceptable.

 

[ChrisQ]

Just noticed Steve's edit - so far I have bought two kits. The first is the Madman's Deluxe 8. The guy's web page says it will run on 6-12V, but the directions on the kit just tell you to hook it up to a 9V battery. Had I read the website more carefully I would probably have not worried about this just yet.

However, the kit I bought for the big E came with a 6v power supply even though the site says "no power supply included".
The instructions say "Never use a power supply that's more than 9 volts for this kit."

As for the rest of the small ships, I do not want to spend $40 a pop on another 8 kits or so. I figured I'd do the first couple with pre-made kits and then after I've learned a little I would just buy the blinker boards and learn how to the models from scratch. In that case I will still need to understand how to make sure the leds will handle 12V.

For that I will read the sticky on LED's

 

[shrtrnd]

This is an idea for you. When you start building your own lighting for your ships, look into the circuits and kits for fading LEDs, or color changing LED's, instead of just blinkers. I've been impressed by the effects some of these LED circuits visually, and it would give your ships more the effect of being 'alive' with activity, rather than just the 'ho-hum' of blinikers.
Just a thought for you to consider.

 

[ChrisQ]

Thanks, shrtrnd. Fading led's are already on my radar. As are sound effects.

 

[ChrisQ]

I just came across a seemingly excellent idea while reading up on voltages.

If I set up my power supply using a 12v as positive and 3.3 as ground, it would give me a current of 8.7v which is pretty much perfect for my needs.

Will this work out as intended or will I come stumbling out of the smoke filled basement with bloody stumps where my hands used to be?

 

[(*steve*)]

This might work if you placed a load on the 3.3V rail which drew more current than the load you were placing between the 12V and 3.3V rails, otherwise it could be messy.

The 3.3V regulator will expect to be a current source, not a current sink. Weird (and possibly bad) things may happen if you try.

 

[ChrisQ]

Yes you are correct; it would work in some circumstances but not for me. I just found this from another source:
"If you DO have a sense wire for the 3.3v. , connecting the the 3.3 v. part of the supply, using the 3.3v. voltage as a buck voltage against, say the 12v. to get 8.7v. will not work. You will see 8.7 v. with a volt meter but when you load that 8.7v. circuit the power supply may go into protective mode and shut the whole supply down."

So I will not be returning the box of LM317s I just purchased. I searched and read some of the previous threads people have started here on how to design their voltage regulators, however I am not sure how to compute my specific requirements for heatsink, capacitors, etc.

I will start my own thread in the Circuit forum so hopefully you and others can get me started.

 

[ChrisQ]

Update:

After completing the power supply used to test the models on the bench I have gotten the first model painted and wired. I am just starting on sealing the seams but she's lit up. I started with this one because it was extremely simple to light and good practice for a noob. 2 jumbo white led's and one 3.3 white for the nose.

The U.S.S. Defiant

Now before I can mount this in the Star Trek Room, I need to wire that room and get another 6v power supply. I have found that I can purchase a 6v wall wart that will push 1.5 or 2A so that will be the way to go. No need to modify another ATX power supply for that.

 

[davenn]

looking good, well done
I did similar things with the enterprise A and D models in years gone bye

cheers
Dave

 

[ChrisQ]

1) if you need anything like 12V at 18 amps I will be very much surprised. For LED lighting I would be surprised if your total current draw exceeds 1A.

Ok I need to ask a question now that I think I have a little bit better understanding of things.

I had purchased a 6V, 1500mA wall wart a while back and am now about to get busy wiring the room. But since I have learned to use the LED calculator I realize it was not such a sure bet that 1500mA would be enough for all of these ships. So I need some verification of my math to make sure I understand this right.

I have learned that a common 3.3V white LED draws 20mA or so. When you do the resister calc you plug in 25mA just to be safe. I used this value as a base and extrapolated from there.

The largest ship I am building has 56 of these white LED's so by my handy Windows calculator, just that one ship = 1400mA at 25mA per LED.

Therefore I am figuring that all the other ships in the room with their 5 to 15 LEDs will probably at least match that so I am looking at between 2A and 3A by the time the last ship is plugged in. Since I have not planned out the lighting for these ships, that is my best guess at present.

Add on some LEDs for shelf lighting and other projects in the room (could end up with as many as 200 LEDs on this circuit) and it seems that I am back to using an ATX power supply for the job. At least I know the ATX will not burn up from being overworked, and I will put a 5A fuse on it to protect the circuit.

Please feel free to confirm or refute my thinking and add any suggestions. The two requirements I have is that the system runs on 6V and is activated by a single switch.

 

[(*steve*)]

There are several issues.

The first is that you will probably not want all the LEDs operating at 20mA -- they may be *very* bright.

The second is that if they are rated for 20mA, then 15 mA is safe, 25mA IS NOT.

Thirdly, if you have red, orange, yellow, or green LEDs then you may be able to have two in series.

I would calculate the minimum safe value for the resistors (use 20mA as the current) then see how bright the LED is. You may decide to use a larger resistor value in order to get a dimmer LED. Try each type of LED out and figure out how bright you want it to be, and therefore the value of the resistor.

In a darkened room you may get away with under a mA each. I would be tempted (if I were going for realism) to have the navigation lights fairly bright (say the full 20mA), Any lights illuminating the exterior (e.g. those illuminating the vessel's identification etc.) dim enough not to overpower other LEDs, and finally lights representing "windows" etc at varying at possibly quite low intensity.

The overall effect I would try to achieve (and your aim may be totally different) is that in darkness you see more effects than you under full illumination -- it would lend it a type of realism.

To be even more clever, you could fit a sensor somewhere so that the bright navigation lights are dimmed in very low light conditions to improve your movie watching experience.

 

[ChrisQ]

Thanks for the reply, Steve. In truth, for my first ship I figured out what LEDs I was going to use for it and then asked the counter person at the electronics shop for help with the resistors. I will probably try to compute them myself for each ship I am building and then check my results with the expert at the shop until I am doing it correctly.

However, when you visit ledcalc.com, and hover your mouse over the question mark for Desired Current, it states that most LED's run at 20 to 30mA and 20mA is a good value to use if you are not sure of your specific LED.
Should I be ignoring that and calculating for 15 instead of 20?

Even at 15 or 20 it will still put my total power requirements over 1500mA and possibly 2A by the time I am done. I don't even want to screw around ordering a 2A wall wart. I have already converted another ATX supply tonight and just need to build an LM338 circuit for it so I can regulate the output to 6V.
I used an LM317 on my bench supply but I will never surpass 1.5V on the bench. I need the LM338 for up to 5V.

Using the variable output will also also enable me to dim the lights even more should they be interfering with the movie watching.

As for the brightness of the ships, that is indeed an area of concern going forward and as I build each one I fully intend to try different resistors to achieve the proper effect. Since I have completed the Defiant I am ready to get the room wired so I can see it in action. After that I'll have a better idea of the brightness required, and I will also be able to test them out in the room before sealing them up.

Thanks again (if you made it this far )

 

[(*steve*)]

(if you made it this far )

Yep

A major point of my post is that you would probably want different brightness on different LEDs.

Have you tried these LEDs at 20mA? Do you know how bright they are? Have you considered what 100 of them at that brightness would look like? Your model (unless it is about a metre or more in length will probably be too bright to look at (OK, slight exaggeration)!

Your original post said the LEDs were 20mA and you were using 25mA "for safety". Excess currents will kill LEDs. I was looking at the specs of some 20mA LEDs a couple of days ago and the specs suggested a lifetime of only 1000 hours at 20mA. Yours may have significantly greater lifetimes (I would normally expect 20,000 to 50,000 hours) but increasing the current will dramatically reduce this.

 

[ChrisQ]

Yep

A major point of my post is that you would probably want different brightness on different LEDs.

Have you tried these LEDs at 20mA? Do you know how bright they are? Have you considered what 100 of them at that brightness would look like? Your model (unless it is about a metre or more in length will probably be too bright to look at (OK, slight exaggeration)!

Your original post said the LEDs were 20mA and you were using 25mA "for safety". Excess currents will kill LEDs. I was looking at the specs of some 20mA LEDs a couple of days ago and the specs suggested a lifetime of only 1000 hours at 20mA. Yours may have significantly greater lifetimes (I would normally expect 20,000 to 50,000 hours) but increasing the current will dramatically reduce this.

Now I understand. The model on the bench right now will be using several interior LED's to illuminate over a hundred windows, and then several other LED's on the surface as navigational lights and the like, On the surface lights I will first try using resistors based on 15mA and if they are bright enough for me that is exactly what I will do.

The model that has 56 LED's is indeed a meter long. Here is the one that inspired me:

If you watch the video, you will see at just before 3:00 that it has 2 modes, and uses different LEDs for each mode. So it's not really that bright. I will normally operate it in Warp mode which does not use as many of the LEDs all at once. I can use the ship's 2nd mode as a lamp.

 

[(*steve*)]

Here is the one that inspired me

That is indeed inspiring. Someone went to a lot of effort.

 

[ChrisQ]

Hello Steve and everyone. Update to my thread:

In the middle of building my ships I stopped to build a computer console to replace the stereo cabinet with a PC tower shoved in it. It still sucks but it's much cooler than a half empty stereo cabinet. After many months I am finally done and now can return to building the ships. The pc is water-cooled. The base of this console also houses that ATX power supply I was previously talking about modding to supply 6 volts to all the models. It's running strong and ready to power 100 ships if necessary

The console In daylight
In normal viewing environment

Since I had a big empty space in the middle, I built a little diorama of a ship's engine room in the base and used the reservoir from the water-cooling loop as the warp core. This is what took me so long (at least 8 weeks working a little each night):
http://img.photobucket.com/albums/v260/Kraq/DSCI0163.jpg
http://img.photobucket.com/albums/v260/Kraq/DSCI0170.jpg

The buttons on the console control the PC inside and the power supply for the models. There is a digital voltmeter that monitors the voltage on the power to the models.
The monitor that is built into the console displays LCARS readouts while the screen on the wall is for watching the shows.

And this thing took me so freaking long I almost set it on fire on numerous occasions. I am glad it's done so I can get back to lighting up starships. I was about halfway done Voyager when I decided I needed to build this, so hopefully it won't be another 5 months before I can post some more progress.

 

[KJ6EAD]

If you installed a track or monorail lighting system and powered it with 12VDC you could use it as a mechanical suspension system for the models with one or two connections to the track and use individual regulators on each model/kit to reduce the voltage as necessary. It would be relatively easy to move or reposition models and would accomodate additional lights to sofly illuminate the model hulls so they wouldn't appear as disembodied points of light in space.

 

[ChrisQ]

I thought about that in the beginning but there are to be so many models of varying sizes spread out in so many points around the room that its not an option. It wouldn't be a single track; the room would look like a train station. It's easier just to run a single circuit around the perimeter of the room and then run leads out to each model as I get it built.

If I could figure out how to take pictures in this room properly, I would post some. Right now, it's either blinding bright with a flash or pitch black with no flash and I have no idea how to set the camera to take a good pic at the correct lighting. It never comes out even close to how it really looks.