Sunday, November 29, 2015

Myrtenaster Prototype Build Write Up Part 2: Pneumatics

Time to start the handle and add the pneumatics.

I bought a bike tire inflator (Genuine Innovations Ultraflate Plus CO2 Inflator) to provide a quick burst of air. Unlike Crescent Rose, Myrtenaster doesn't require much air, just enough to shoot out some glitter.

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In order to shoot air, it needs these CO2 cartridges.

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The only place to store the inflator is in the handle. The batteries for the lights will also go there but that will be when I have the RGB LED circuit up and running properly. But first, the cylinder full of glitter has to be able to attach and detach from the handle. Twist some craft foam into the center to hold a rod of some sort.

Had an old LED flashlight lying around. Took it apart.

The flashlight cone piece works perfectly for the handle. I'll paint it later. It even fits one of the Vex gears I had lying around!

Fits nicely.

Glued the cone piece on the gear, cut a piece of cardboard paper roll tube, attached the bike inflator and the rest of the side guards to the cardboard piece.

Now to add the parts for the pneumatic system.

 1/4" ID NPT clear tubing, 1/8" ID NTP clear tubing, brass tee fitting 1/8" NTP, Campbell Hausfield 1/8" NPT Tank valve, KQ2H07-35S, and KQ2H07-34S. Attach them to the tee fitting by applying teflon tape to the threads of the pieces and screwing them together. Like so.

Not pictured was attaching the blue tubing and the respective KQ2H07-35S part. The other wing guard of Myrtenaster was fitted on to open and close. Fins were fitted to spin the cylinder manually, no space for a motor powerful enough to spin it. Would have been heavy too.

Open and closing of the wing guards are made by use of velcro.

 Ran a test shooting of the system.

Works as intended. 

Things left to do:
-solder electronics
-mount electronics
-put together pneumatics
-mount pneumatics
-create handle(handle not complete)
-attach handle


Myrtenaster Prototype Build Write Up Part 1: Basic Chassis

Let's get started.

Started by buying a cheap China made light saber; it glowed green.

Took  it apart and...

Yuck, no resistors. Counted 20 LEDs in parallel connected to a push switch and 3 AA batteries. For the record don't hook up LEDs without a resistor in this situation. You will severely shorten the life span of your LEDs. Bad practice. The plastic blade is now ready to be used.

Next, we need to build a chassis of sorts. A skeleton to hold all of the pneumatic and electrical parts to the prop. To start, I decided to build the barrel first. Pretty simple, a wooden dowel rod and two discs cut out of leftover foam board. Poke a hole in the middle of it and stick the dowel through.

Myrtenaster has 6 slots on where the dust cartridges lie in the barrel. To simplify, I measured and drew 6 lines all meeting at the center, like how one would cut a pizza into 6 slices. I then hot glued rectangular pieces of foam board to create space for the 6 glitter cartridges.

I bought a glitter pack from Walmart. It had all the colors I needed and was the right size for the barrel.

I lied, the shakers ended up being a bit big. However, it ended up working out as I first covered the outside of the barrel with stiff white felt and cut out the appropriate space for the shaker to fit. Worked out quite well.

Since the electronic parts haven't come in yet, I went ahead and decide to start the pivoting side support that allows this whole part to pivot off the handle. I used Tatsutetsu's free blueprints as a guide to draft the support patterns to the size of my current prop, which is bigger than what his prints show.
Way bigger than the prints. An earlier stage test arrangement of parts.

Next was to attach the blade to this barrel. This barrel is also suppose to spin so in order to do so, two circles of foam board were cut and a hole was poked through them. Because there are not suppose to spin with the barrel, they can not be attached in any way to the wooden dowel rod. Side rectangular pieces were added for support of the two circles and as a start mount for the blade. Extra room was made for the electronics later. They are attached to the foam board by 2 pairs of wooden dowels through pre-made holes in the blade.

 I then attached the side supports to the current prop by cutting a small polygon piece and poking a hole through that and the side supports. A wooden dowel was put through the holes to create the pivoting effect.

Not bad for progress. No problems yet.

Things left to do:
-solder electronics
-mount electronics
-put together pneumatics
-mount pneumatics
-create handle
-attach handle


Myrtenaster Prebuild Write Up

Go right to part1
Since Crescent Rose is now in the testing and refinement stage, I am left with loads of time.
I have decided to create Myrtenaster.

In the show, it can shoot dust.

and change blade colors.

Also it shows the barrel moving in operation

 Additional images show the operation of dust and reload mechanisms.

Dust expulsion mechanism

Hinging mechanic

Already this is going to be simpler than Crescent Rose due to the lack of needed movement that Crescent Rose demands. All Myrtenaster does is shoot dust, light up in different colors, hing/unhinge and spin the barrel. Compared to Crescent Rose, it is simpler but Myrtenaster still requires a good amount of engineering knowledge to emulate it all. Especially when you have to pack all of that into something that is smaller than Crescent Rose.

The main goal here is to recreate the hinging, have dust blow out and have the blade light up. The spinning barrel will be secondary since it is a minor effect and I am worried about space issues. If everything else fits and works well then I will try to add the spinning barrel effect. Otherwise don't expect it.

Hinging the prop is easy. The image for the hinging mechanic basically shows how it will be done. One pivot point and three attachment points.

To shoot dust, it would be much like shooting projectiles, abet tiny ones. Projectiles can safely be shot manually, through a spring powered mechanism (think of the Nerf guns that you have to pull back before shooting) or through a burst of air (think of the Nerf guns that you have to pump air into). There are ways in which you can shoot projectiles through electric means but those are no good for shooting tiny dust like projectiles. In terms of trying to shoot tiny dust like particles, air would be the best way. After all, it is how the industry does spray painting and air brushing (All use air to carry tiny paint particles to the target area). Due to the fact that the prop is fairly small, the air shoot mechanism will have to be compact. This means using canned air or something similar.

Having the blade light up is a bit more challenging. Myrtenaster shows 6 different colors.

Purple, white, yellow,blue, red, cyan
Essentially, the blade will have to light up in 6 different colors. I decided to make my own circuit because finding a light source that can light up in 6 different specific colors is either non existent, expensive, too big, or not having the control I needed. The choice to go with individual LEDs and not LED tape is that I needed a 360 full circle degree light to light up a lightsaber-like blade. LED strip/tape at most can go only halfway since the LEDs sit on a surface. To get the blade to light in 6 colors with individual LEDs, you can buy batches of different color LEDs or buy RGB LEDs. RGB LEDs are LEDs that can light up in red, green and blue all in one LED. What is interesting in this case is that if you take a look at the 6 colors, notice that these colors all appear on the RGB color model.

 Add the fact that space will be limited and it makes it very convincing to use RGB LEDs. So it will be done. With that decided, the next thing to figure out is circuit design. RGB LEDs don't do much themselves, they need a corresponding circuit to power it all up. In LED circuit design, there are a couple ways of doing this.

One way is to connect your LEDs in series with one resistor.

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Another way is to connect them in parallel with a common resistor.

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Or connect them in parallel with each LED having it's own resistor.

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Or one can use any combination of the above.

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And another way is to is a current regulator.

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Or one could use a voltage regulator instead.

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There are many pros and cons to each.

Doing LEDs in series with one resistor is easy to calculate and put together but it requires a lot more source voltage to power a whole setup, especially when running 10+ LEDs. In addition, if one LED goes out, all of them do and as the voltage lowers with continued use, you will begin to see an interesting brightness effect as the voltage continues to drop where the first LED is brighter than the second, which in turn is brighter than the third...and so forth until the last LED is completely dim. Aka no brightness control.

Doing LEDs in parallel with a common resistor requires a bit more calculations and soldering but you can run many LEDs off a lower voltage battery and having one LED go out will not affect the other LEDs. However, a common resistor means that each LED will get different amounts of current due to variations that come in manufacturing, and each LED will give off different amounts of lighting as a result. Not that great with brightness control. Doing LEDs in parallel with each LED getting it's own resistor fixes this somewhat as a resistor given to each LED will equalize the current given to each LED and in turn give a better brightness control. Sounds better but still not using this type of design.
Doing a combination of series and parallel design will, if well done, allow the designer to maximize brightness and efficiency but a full string of LEDs in series will still turn off if one LED goes out and a loss of brightness will occur.

A less common way of creating an LED circuit is to use voltage/current regulators in addition to resistors. Resistors are good for getting the right amount of current to your LEDs... at one point in time. Truth is, battery voltage is not constant throughout it's use. As in, when you make your calculations, you assume that the battery voltage is constant before it drops dead. That is not how a battery behaves, as you use it, the voltage drops to different levels at a non linear rate. So as the voltage drops, you get a dimming effect that reduces the brightness of your LEDs. To fix this, you use a voltage regulator or a current regulator that keeps the supply voltage constant even as the battery drops in voltage. Issue here is that the calculations are a bit more complex then doing it through resistors.

Considering that I will be using RGB LEDs and that I want the best robust brightness, the current regulator is the best design for me as each color in the RGB LED turns on at different voltages. The only thing constant between the colors is the current required.

Alternatively, if the RGB LEDs are not up to my standards, I can use a high power  RGB LED. Due to the power requirements of one of these devices, I will have to use a heat sink and any electrical components in the circuit will have to handle high amounts of power. I will go into more depth about these types of LEDs if the low power option does not work.

This'll be an interesting project.