Lights & Sequencers for Faux tank treads

[Conradaroma]

So, I thought I'd post here for any ideas at all.

I'm working on a fairly significant (for me at any rate :shock: ) project for the playa this year, and need to start working on some lights.

What I'm looking to do is make some faux tank treads out of sequenced lights, so it looks like they are moving forward in the night time. There will be quite a few lights, two different treads, each being about 20 ft long, so that means I will have one long light around the entire tread (just over 40ft or so), then I would like to have faux tires driving this track, so smaller circular lit shapes that drive the outside one.

Now, I've had a couple of thoughts on how to light this, one would be to use individual lights and sequence them, the other would be to use light strands or something. Alternatively, I could use EL wire and sequence bands of that...

My only problem is that I'm not sure what would be the best way to make the sequencer. I figure I could buy one, but will I be able to find one that can do all that I need it to do? Alernatively, could I program one using a POS computer or something? I'm a linux guy, so could get an old laptop and give a try to programming something out on the serial port...dunno how that would work though.

anyways, this guy's looking for approaches, so if you know of any tips you could give me, I'd greatly appreciate them. And then on playa if you're around I'd love to stop by and give you a lift somewhere.... ;)

Kippler

[robotland]

It sounds like you're ready to put a LOT of work into this, but here's a low-rent solution that might bear experimenting with: Using existing Xmas light strands. It's off-season now, but some have to be available from SOMEWHERE- And some have decent "chaser" settings. Look for LED lights over incandescent, for energy efficiency. Perhaps the suggestion of separate "treads" could be made with thin slats of wood covered with mylar or foil, to reflect the light.
Also, ask Dragonfly Jafe what HE'D do.

[AntiM]

If you'd prefer encased lights: I got a sequenced rope light at Spencer's, cheap and very pretty, 120v, but I'm willing to bet 12v couldn't be far behind.

[robotland]

Or one could invert.

[phil]

Hi, Conradorama, er, aroma :->,

I have no idea how realistic you want to be, but let me tell you about my high school physics class, where the teacher asked us to determine the angular velocity (or was it momentum? who cares?) of a rolling tire.

It turns out that if the car is going 10 miles per hour, the top of the tire is going 20MPH forward, the front of the tire is going 10MPH down, the bottom of the tire is going 0, and the back of the tire is going 10MPH up. This shocked me to the extent that I remember it these 40 years later (I graduated in 1965.)

It turns out this physics is actually correct. If you watch a bulldozer or tank running on treads, the bottom treads actually don't move, and you can see it - the tank or bulldozer runs forward over the treads that lay on the ground. ( Visualize putting your foot in front of a bulldozer and letting it run over your foot.) The top treads have to move forward faster than the tank (twice as fast, in fact) to lay down and stay down for the tank to roll on over them. (With round tires, there's not enough time to see this happening.)

So if you want your 'tracks' to appear realistic as you ride along on them, then have to be timed to that the track on the ground appears to be motionless as long as your vehicle is above them, then pick up at vehicle speed, go twice vehicle speed on top, then vehicle speed down to the ground.

Or don't worry about it. As you wish.

[Mister Jellyfish Mister]

Thanks, Phil. That was just cool to read.

[dragonfly Jafe]

...another way of stating the desired effect is to have the speed of the sequencer equal the speed that the vehicle is traveling.

For instance, say you are zooming along at the max. speed of 5mph... if the sequencer is also going 5mph (with the top moving forward and the bottom moving backward), then the top will appear to be moving at your 2x speed of 10mph (5mph vehicle speed + 5mph sequencer speed), the front and back tracks will be moving at 5mph (just the sequencer speed), and the bottom track will be moving at 0mph (5mph vehicle speed - 5 mph sequencer speed).

How you make a variable sequencer that can do that, I have no idea (it's why I'm building one for real...seems easier to me!)

[phil]

...another way of stating the desired effect is to have the speed of the sequencer equal the speed that the vehicle is traveling
>snip<

I think that might be right, but my powers of accurate visualization fail me.

How you make a variable sequencer that can do that, I have no idea (it's why I'm building one for real...seems easier to me!)

I know people who have their bikes hooked up to EL wire 'cartoon frames' so that when they pedal faster, the animations speeds up. I've looked at their bikes, and there are sticky things on the spokes which appear to trigger certain frames to be on. Sorry, I have no clue how it was set up, only that it worked.

[Token]

How you make a variable sequencer that can do that, I have no idea (it's why I'm building one for real...seems easier to me!)

A counter that drives a demultiplexer which sequences the lights. Input clock can be derived via magnetic or optical pickup from the axle.

Place 16 points on the wheel and a pickup. Can use a Hall Effect device (old style automotive distributors circa the 1970s) or use a photo diode/LED with some reflective tape or an old computer mouse (not the new ones that light up but the old style with the rolling ball). Feed the signal into a 4 bit counter. Use counter lines to drive the demux. Set demux input to high. connect demux output to FET gates for switching.

This would cause one light to chase in the group of 16 lights proportionally to the rotation of the wheel.

You can add more groups of 16 lights by driving additional demuxes from the same counter. Just interleave the 16-light groups to taste.

Parts:

74LS93 - Counter or 74LS193 for Up/Down counter (when in reverse count down)
74LS154 - 4 to 16 line demux
Power transistors to perform switching of the demux output lines.
Misc. power and supporting passive components.

Should cost in the $50 ballpark for parts.

You could increase the number of pickup points and low speed accuracy by employing a divide by 2 counter or somesuch.

[Token]

I'm a linux guy, so could get an old laptop and give a try to programming something out on the serial port...dunno how that would work though.

Sorry I missed that part. There is indeed a way to skin the cat with some clever coding.

You can set the state of the parallel port pins from C via a Linux library:

http://parapin.sourceforge.net/

Good general info on legacy ports can be found at:

http://www.beyondlogic.org/spp/parallel.htm

They are Windows-centric but the info still applies regardless of OS.

You could use one of the control lines to sample the axle speed and the data lines to sequence the lights. The only hardware needed would be the Switching Transistors for the lights.

[Megaflow]

You an use El wire and run a Cat9 sequencer to make the treads look like they are moving. We did this last year with our Chariot and had sequencers running the wheel spokes and the 6 channel horse making it trot as we drove. The Cat9 has many patterns and runs 10 channels with a speed control. They are around $75 from Coolneon. It takes alot of wiring to make it all happen but it really looks cool when you get it right. Be sure to dust proof all your wiring connections and sequencers.

[robotland]

I just had to re-read this whole thread, because it made my brain feel so good the first time!

Fszszt. *sigh* Friszsitzit. Endorphin Release Aaahhhh.