This is for other Ghostbusters Props that don't fit into the categories above.
Thanks to Tristen (killer96) releasing his amazing digital files for the GB2 Tripod Traps, I ended up building a set of these over the past few months for our South Australia Ghostbusters display table.
It was a really enjoyable build, and I highly recommend building these for your franchise!

I'll be posting updates as I go here, as these props aren't entirely finished yet (they're usable but I have some further improvements to do).

I'll post individual posts below so I can keep things more manageable and easier to read.


Obviously we're talking about the devices used in the GB2 "We're Back" montage at the Orrefors jewelry store, as seen here:
Yes, Tristen spent several years digitally recreating a prop which was on screen for SIX SECONDS :lol:
(Worth it! :heart:)

You can find Tristen's thread here, with a link to the GitHub files: ... 6#p4977826

  • I'm not super interested in screen accuracy but Tristen's files/instructions will help you with that if it's important to you (links to accurate parts, metal cutting plans, etc)
  • I'm only building two of these, not all four
  • Technically they're known as "Polarity Rectification Tripods", but for simplicity I'll call them "Tripod Traps"
  • At this time I'm not bothering with the small yellow control box and the large black box
  • No sound effects
Basically these are just going to be "something cool to put behind our display table at events".

First Unveiling
The South Australia Ghostbusters had an event in March 2023 at our local Museum, so I wanted them ready by then. Here's the finished product, where they're at as of right now:

And a brief video demo:

(To be continued below...)
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Gathering Parts

Tristen's instructions include sources for many of the screen accurate parts needed, but many are either sold out, or don't ship to Australia, or outrageously expensive if they do ship here. So I went with "close enough", even though in some cases that came back to bite me later.

For electronics, I wanted each tripod to be 100% powered by 5V USB powerbanks. I wanted everything to run off 5V (no 12V components).

The first thing I picked up were the photography ball-mount fittings for the tripod antenna heads, close enough to the original. I bought two packs of 5 because I need 6 total (3 on each tripod):

Then 10-segment red LED bargraphs:

I needed an analog gauge for the front of each, but I wanted them to actually operate. Powering a genuine VU-Meter seemed like a headache without a complex control circuit (I gave up researching this) so I went with Volt Meters.
I knew I'd be controlling it from an Arduino which can do up to 5V of PWM, but the only suitable gauges I could find were 20V. All the others were too large to fit (I had already printed the enclosures by this point so I didn't want to have to Dremel out large chunks to fit different gauges). Luckily they were cheap, shipped quickly, and ended up being super easy to modify:

For the center column I bought yellow lighting gel and diffused 5V Warm White LED Strips:
(5V was intentional, I didn't want to have to install a buck converter to power 12V).

For the tripods, the genuine article were too expensive. I happened to be at K-Mart and saw they had selfie ring lights discounted to only $15 each. They weren't quite what I was looking for and I was worried about stability and installation, but for that price I couldn't say no them:
For comparison here's what the genuine article looks like:
(AU$15 is a LOT better than AU$200 :lol: )
So it's worth noting that my selfie tripods don't have full-length legs, so there's a potential risk of them toppling over if they're not setup on a stable surface. Luckily I think the tripods ended up being light enough that this shouldn't be a major problem, especially given that they're setup behind our display table instead of where the public could knock them over.

Another option is to tie sandbags to the base to weigh them down more if needed.

Also bought some lengths of black curled telephone cable and various electronics components (nothing too exciting).

Those damn acrylic tubes
The centre columns require two lengths of clear acrylic or polycarbonate tube, 3in OD on the outside, and 2.25in OD on the inside ring (which is then wrapped in the yellow lighting gel and the black electrical tape stripes).

Out of everything these proved to be the most problematic. Finding imperial size tubes in Australia is damn year impossible.

I gave up on the inner tube, I figured I could find another solution for this. So it was just the outer tube, which holds up a lot of the weight of the antenna head.

I bought some 75mm OD acrylic tube on eBay from an Australian seller. It shipped without tracking. After 3 weeks of waiting I contacted the seller to ask where it was. They never replied, they just instantly refunded me. I bet they didn't even ship them.

I contacted a local wholesaler that listed 75mm acrylic tube on their site. They said they only sell in 2400mm lengths and they don't cut to size. I only need 430mm total so this wasn't going to work. They gave me the phone numbers of their 3 retail clients. I called all three. The first two said "sorry, we'd have to order it in, which means we have to charge for the full 2400mm lengths". The third said "if only you had called before yesterday, we had 600mm of that exact size but someone just bought 200mm of it, so we only have 400mm remaining and we'd have to order the rest in for you".

Just about tearing my hair out at this point, it's 3 weeks to the museum event and I still don't have plastic tube.

I happened to be out shopping and I saw these bottles of imported water on the shelf. They were perfectly cylindrical all the way down, no imprints and a removable label. I grabbed a ruler from the stationery section and measured, and they were just about the right length:
So I bought two. They're flimsy but I figured they'd do the job for the event.
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Printing and Painting
Tristen's diagram of the parts:

I printed the pieces mostly in grey PETG on my Ender 3 V2:
Print quality was pretty rough, but I'd rather do more sanding/filling work later than have to reprint pieces.

Tripod Heads test fitting (note the huge gaps due to 0.6mm nozzle print):

(It's the underside, nobody will see this)

Then came the sanding, filling and painting. Some pieces needed more work than others. Primed everything in Rustoleum Grey Primer.

I decided on Rustoleum "Satin Heirloom White" as the main colour for the body and it worked perfectly:


For the lower V-ring piece I really built up the layers of Primer Filler to smooth it out before painting and I'm glad I did, it looks awesome (and sanding it by hand would have been very finicky). There's some layer lines remaining but not in the most visible places:
I ran out of Primer Filler or I probably would have used it on other pieces too.

Rustoleum Aluminium Silver on the Antennas, with the individual rods hand-painted copper colour:

I did try copper foil tape but I just couldn't get it to work well, maybe with more time and practice but it's a technique I just couldn't master before the deadline.
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Decals & Labels

The hero props have decals on them, I could have been lazy and gone with printed clear labels but I wanted to try the pack of Film Free Waterslide transfers I had:

Most of the decals are just small amounts of text and these sheets are expensive, so I filled the rest of the sheet with a bunch of other labels (trap, goggles, etc):

For comparison, here's the traditional transfers I tested on a trap frontplate, note the film all around them:
(They didn't stick very well to the shiny acrylic)

And here's my test of the film-free transfers:

So yes, definitely onto something here.

Warning: These transfers require heat to permanently bond them to the surface
Heating gently to bake the transfers in an oven wasn't an option for these, so I used a hairdryer carefully. Even so, some of the thinner PETG parts lightly warped and I had to press them flat again. Not a major issue because they get bolted down into place, but I wouldn't recommend trying this on a PLA print.

Here's the first transfer of the side panel, it didn't bond all the way to the edges but I actually kind of liked the way it looked:

Second one turned out much cleaner, aside from a few realistic-looking blemishes:

Front panels turned out nearly perfect, glad I practiced on the less-visible sides first:
You can still see some remnants of the rectangular waterslide transfer film around some of the labels, once it was completely dry I was able to gently rub this off with isopropyl alcohol.

The last remaining label is the side metallic V-Ring Antenna label, as seen on the hero prop:

I found the amazing digital files by Demon Vice Commander posted here:

The scale was off, it didn't line up with the screw holes. So I scaled them to the correct proportions for now and printed some out on the waterslide labels (the ones with the film, as I didn't think that would matter here). I transfered them onto aluminium foil tape and cut them out:

It's alright I guess, but my laser printer wasn't doing a great job of the black printing, the edges were pretty rough, and I wanted them to be thicker (maybe 1-1.5mm thick) so I could bolt them on instead of sticking them. Maybe I could laser cut some thin acrylic the correct size, paint it silver, then attach it to that? Or, find a thin aluminium sign roughly the right size, sand the label off, stick mine on, and file it to the correct proportions? Or, 3D print it?

Given the rapidly approaching deadline and the huge amount of electronics I still had ahead of me, I put this part of the build on hold and left it out for the museum event, so we just have four unused bolt holes on the side of the body.
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Tripod Mounting

My selfie tripods had standard 1/4" photography screw fittings on them but barely any length of threading, certainly not enough to run all the way inside the body so I could bolt them securely from the other side. We're talking about barely 10-15mm of threading here.

I tried using one of the spare ball-mount fittings as an adapter but this didn't work, they wouldn't reliably stay vertical.

So I decided to 3D model an adapter to attach the ball-mount fitting beneath the trap body and hold it firmly in place, but still be able to unscrew the tripod from the body for easier transport.

Not screen accurate but I'm really happy with how stable and secure it is.

Center Column
I needed something strong to hold up the main antenna head along with the inner light bar, especially that the outer tube was going to be a flimsy plastic bottle. So I took measurements and 3D modeled a centre tube which locks into place at both ends:
Obviously it needs to let light through so I printed it in transparent PETG:

Test fit:

To better hide the layer lines and further diffuse the light I wrapped it in a layer of baking paper, and then a layer of the yellow lighting gel around that. I used clear tape and aligned the joins on the back of the tube so they're mostly out of sight.

Plastic bottle was cut to size and taped in place, again with the join hidden on the back of the tripod.

First test lighting looks pretty good:

And the final installation with the electrical tape stripes (lining these up evenly was pretty challenging, best I can suggest is go slowly):
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OK, let's wrap this build up because I'm getting tired :lol:

Super simple here. Each Tripod has:
  • An Arduino Nano to run everything
  • A 5V USB rechargable powerbank to power everything
  • 5V Warm-White LED strip lights in the center column
  • Cool-White LEDS in the top antenna
  • An Analog Volt-Meter on the front panel
  • A 10-Segment red LED bargraph on the front panel
  • Flashing lamps on either side of the arms (V-Ring Antenna arms)
Analog Gauge
As I mentioned earlier these are 20V, which means the 5V PWM Arduino pins can't move the needle more than 25%.

Luckily they're easy to modify. The front panel is held on with tape, and inside you'll find a single resistor (I don't remember the original value):

So I snipped it out, soldered the leads together and connected it to the 5V Arduino pin. As expected, it "buried the needle" right off the edge of the gauge. So I added a 5K resistor, this was too high (it barely moved the needle). Dropped to a 0.5K resistor, it buried the needle again. I didn't have anything between 0.5K and 5K so I just kept chaining 0.5K resistors until I got the needle to sit roughly at the end. The magic number for me was 1.5K, I was able to use analogWrite() on the Arduino PWM pins to smoothly move the needle up and down. Sudden movements cause bouncing (eg if you drop from 100% to 20%), so I wrote code to move it more smoothly instead of jerking around all over the place.

When the Arduino has fully booted it jumps to the middle of the gauge (125) as its starting position.
Whenever the TimedAction callback runs, it determines a random New Position, and a random Delay before changing to the next position:
Code: Select all
int currentLevel = 0;
TimedAction gaugeTimer = TimedAction(200, []() {
    analogWrite(ANALOG_METER_PIN, currentLevel);

    currentLevel = currentLevel + random(-25, 25);
    // minimum 50
    currentLevel = (currentLevel < 50) ? 50 : currentLevel;
    currentLevel = (currentLevel > 255) ? 255 : currentLevel;
    gaugeTimer.setInterval(random(400, 3000));
As you can see it moves either up or down by up to 25 (-25 to 25). And then it waits between 400-3000ms before the next change. There are limits there to prevent it dropping lower than 50/255 (~15%) or higher than 255/255 (100%), so it always has some kind of reading visible. This delay and small jumps up/down definitely look more realistic and prevent needle bouncing.

Here's an early proof of concept demo video:

I'm sure it could be smoothed out further, by randomizing a target reading and then slowly moving there until the target is reached, then choosing a new target. So instead of waiting 3 seconds and jumping up by 25, it would jump up by 1 every 120ms.

Left/Right Red Lamps
I already had some perfect looking VCC red lamp covers from another project (actually an unfinished Warehouse 13 Farnsworth build, where I bought a pack of 10 but only need 1). But they're too big to fit in the holes.
So I 3D modeled and printed these adaptor pieces:

The lamp cover attaches with a few drops of superglue, and the LED itself just push-fits inside from underneath (basically just keep wrapping it with electrical tape until it fits snugly).

I ended up spraypainting them black.

I soldered resistors to the cool-white LEDs I had, but the hardest part was soldering to the incredibly thin telephone wire. You can't strip the plastic insulation off, you essentially have to melt it off. So I pretty much just melted it with the soldering iron in the hopes that I could wrap it around the leds, solder it in place, and then add a few large blobs of hotglue to stop them from coming apart.

Almost looks like I know what I'm doing! :lol:

At the other ends I soldered wire leads with heatshrink so I could more easily attach them to the Arduino without ever having to deal with telephone wire.

Pretty simple this one, just soldered an HT16K33 i2c board to each bargraph. 4 wires to each (+5V, GND, SDA, SCL). Didn't allow enough spacing on the first one so I had to cut a chunk out of the bargraph bezel, but it's not visible anyway:

Also hand-cut a small rectangular window of translucent red acrylic to go between the front plate and the bargraph.


Here's all the components wired up to an Arduino. Power on, short startup sequence, then into the main loop.

Nothing too exciting but it works. This was before I also made the Analog Gauge move in the startup sequence, and improved the randomization code for the gauge too.

There's a video which shows the bargraph animation on the screen-used prop. I don't really like the way it looks, it looks like a broken circuit to me. Also I don't know for sure that the bargraphs were even switched on in GB2. So I just wrote my own simple animation that I liked:

Center Light Column

Here's the center light column powered up with the warm white LED strips attached (they came with a peel-off adhesive backing):

In hindsight, I wish I'd taken the time to simplify the wiring instead of running two wires from each, it would have made life a lot easier later. But I was in a rush. Once the wires were attached and seemed to work, I hotglued them in place.

Final electronics

NOTE: I wired up and connected both the side-box blue potentiometer and front 3-position toggle switch, but neither actually does anything yet. I haven't figured out what I want to use them for, but it's just a matter of writing code to use them in some way.

OK, here's the embarrassing photo. I was designing this on the fly, occasionally swapping Arduino pins when I realised they weren't suitable (or my wires were too short to reach):

What I do love about this is that even with the super bright center column LEDs, the WHOLE device is powered by that single tiny USB cable. If I remember right it was drawing well under 1Amp, my USB powerbanks can do up to 2Amps each.

Arduino Code
If it's useful for anyone here's my code, note that this is still very much in-progress and was thrown together in about an hour (it's not very efficiently written but at least there are no delay() calls outside of the startup sequence).
I'll probably rewrite it when I next work on this project, but after that first event I don't think people were really looking too closely at what the devices were doing.

(Edit: Moved code to GitHub so it always includes the latest version)
Last edited by prodestrian on April 15th, 2023, 8:05 pm, edited 1 time in total.
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Next Steps

Found some perfect acrylic tubes on AliExpress for a reasonable price:

Cut one to size and it's already made things much more stable than the plastic water bottles (especially once it's bolted in place at the top):

Unfortunately the 3D printed inner tube doesn't fit anymore so I'll need to cut the ends off and 3D model/print an adapter. It's not visible anyway so it doesn't have to be a clean fit, to save me printing two whole new tubes.

I also have enough leftover yellow lighting gel sheet to wrap a second layer around and saturate the colour a little better. Haven't made a decision on this yet.

For the USB powerbanks I realised the selfie light tripods came with clamp-on phone holders, they were the ideal size to attach the powerbanks at the event.

The USB cables are long enough that I could potentially have them plugged into a "control box" sitting in the middle of the two tripods, but I'm not worried about hiding the powerbanks for now.

Other little details I didn't mention:
  • The antennas on top collapse/rotate for easier transport
  • The tripods themselves were more stable than I expected when the legs were more spread out
  • I made stencils and spraypainted the "01" and "02" numbers on the sides in yellow paint, with moderate success (had to do some cleanup afterwards with a paintbrush).
And finally, here's a full photo of our setup at the Museum Event (you can see the tripods next to the Vigo painting), it was a brilliant evening:
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April 2023 Upgrades

I need to use these at another event next week (just under 7 days from now) so I decided to be ambitious and get these upgraded before then. Also trying to get in the habit of posting my build logs on GBFans, it makes things easier in the long run (and helps motivate me to keep going, especially on tasks I really don't feel that motivated to be doing).

First thing's first, the code is now up on GitHub:
It may not be useful for anyone but me, but it's always best practice to version control your code.
Also added a README so if I decided to make changes in future I don't have to reverse engineer things.

I've cut the acrylic tubes down to size (approx 215mm long). The cut edge is rough and uneven but nobody will see it, the visible end is still perfectly flat as it arrived.

I've hacksawed the ends off the printed center columns as they don't fit the new acrylic tubes:

But then disaster... I spent 30 minutes trying to figure out why my 74mm print didn't fit on top of the acrylic tube, and it turned out AliExpress ripped me off. One tube is 75mm OD, the other is only 70mm OD. Which means I'm going to have to 3D model TWO different adapters. It's too late to get a replacement so I've asked for a full refund (on account of them wasting my time, plus the traps will no longer match perfectly). Swapping tubes is such a major operation that I won't be bothering to fix this later, I don't feel like cutting and resoldering all the wires for a third time.

Hopefully it's not too noticable that they're 5mm different in size.

With that puzzle finally solved I can jump into FreeCAD and start modelling something up. I'll start with the larger 75mm tube, which already fits snugly to the end of the top piece. It needs to have 10mm of padding to replace the 10mm which I cut off the inner cylinder, plus enough overlap with the acrylic tube (which wasn't accurately cut so I can't measure this precisely).

51 mins (and another cup of coffee) later... It didn't fit, because I was overthinking the design and didn't account for the top piece's inner section. Simplified it right down to just a 10mm tall ring which fits outside this inner section but inside the 69mm ID of the acrylic tube. 37 mins later...

Both sizes fit perfectly as far as I can tell, so now I need to make a start on rewiring everything. I want to simplify the lights in the center column, there's 6 LED strips plus 3 antenna LEDs. So I had 18 wires running out of the center column (6x2 + 3x2). I'm going to make life easier by tying all the grounds together, and trying to chain the LED strips. What I realised too late is that if I run jumper wires between each strip, nobody will be able to see them because it's so heavily diffused.
Much cleaner, now I only have 5 wires running into the center column (3xAntennas, 1xLED Strips, 1xCommon GND)

Everything reassembled and working again:

Disappointingly the 70mm tube is nowhere near as stable as I'd hoped. Maybe I will have to modify it to be more secure someday, or just wait and see if I get the refund from AliExpress. At least now it's easier to rewire things if I do have to swap it out. But it's good enough for the event..

Onto the second trap, this time with the correct sized tube.
Took it apart, modified the inner cylinder, and started working on rewiring the lightbar. It was a faster process, but this is all done too. Should be good to go for next weekend.

Update: AliExpress sent me a partial refund. That's great, except that the seller doesn't sell acrylic tubes individually, which means if I get a replacement I'll have to buy another set. Very clever trick, making me buy 3 when I only wanted 2 :lol:
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