Okay, okay, I know what you're thinking... yet another over-inflated, bandwidth-sucking Ghost Trap build thread. Yes, there are already many amazing trap builds here and I have been following them all myself - most recently Cristoval's great build of Sean Charlesworth's 3D printed kit. I am currently developing prop prototypes of my own, but Sean's design already incorporates all the things I'd ever want from a trap replica and does so in a really clever way. Sure, you don't get the removable cartridge, but I have no plans on installing a containment unit in my home anytime soon and it means more space inside for the cool stuff, so, whatevs...

The ghost trap has always been my favourite piece of Ghostbusting gear. Therefore, I thought I would post my own build here too. I am based in the UK, and when it comes to the finishing of 3D prints, many build threads tend to mention materials only available in the US, so I thought it may be useful to others by documenting the methods that work well for me.

I'm going all out and will be building the 'mega-deluxe' version of Sean's kit. This includes all additional hardware and the Arduino based electronics to provide lights, sound and smoke. However, I plan to make a few customisations to make the trap behave more like it does in GB1:

- MULTICOLOUR LEDs: The original design includes three bright white LEDs for the main lighting with a purple lighting gel for colour, but I would like to be able to adjust the colour and brightness so as to simulate some of the effects seen in the movie.
- CODE EDITS: I'd like the trap to behave like it does in the Sedgewick Hotel scenes as operated by Ray, so a few code adjustments will be needed.
- MORE ACCURATE SFX: Sean includes edited versions of the sound effects from the video game, but I'm not the biggest fan of them and would rather it sounds like it does in GB1. I can't seem to find them anywhere and I think isolating them well from the movie would be near impossible, so I'll have a go at recreating them as accurately as I can.

Right, 'nuff talk. Let's get to it....


First off, I'm printing all the parts in black PLA. For those in the UK, I've had good general results with Amz3d and Sunlu filaments available on Amazon. As I'll be smoothing and painting almost every part, no need to be fancy here and waste time with high resolution. Sean also provides a useful print guide which mentions the parts that require greater infill or a slower print. Otherwise, a standard 0.2mm layer height with a 0.4mm nozzle does the job beautifully:


Next comes the bit that (literally) stinks. Just because this is a 3D print, doesn't mean the final prop has to look like it's made of plastic. That's what I really dislike about the Matty traps - just all shiny and cheapo looking even though it's not all that cheapo. I want to get rid of all the layer lines and print marks, but the only way to do that satisfactorily is to use automotive body filler. Most prop making forums and videos talk about using 'Bondo' to smooth out printed surfaces - specifically Glazing & Spot Putty that can be used straight out of the tube. This is something we can't get in the UK, so the closest is Isopon P.38 Body Filler. Unfortunately, it's a two-part filler meaning you have to mix it yourself with separate hardener - this makes a messy job even messier, plus the fumes this stuff kicks out is enough to get you high as a kite. That may sound like fun, but the smell is as nasty as the paste is icky. In this case though, it's a necessary evil, so let's smear it all over everything we need to smooth out. Isopon provide an application tool, but it's tiny and generally useless, so I find it easiest to wear latex gloves and use my fingers to make sure the whole surface is covered:


I could have been a bit more careful with these parts and applied the filler a bit thinner, but you don't get long before the P.38 starts hardening and we're gonna sand the s**t out of everything anyway. Once everything is covered and left about 30mins to set, the sanding marathon begins. And nobody likes sanding. Not even prop makers. But it has to be done, so I soldiered on by dry sanding the surfaces back down to the plastic with 150 grit sandpaper. This is no fun whatsoever - especially around corners and crevices, but if you persist, you'll end up with much smoother surfaces with all the low spots evened out. This is what I like to call the 'Friesian Cow Stage':


Time to moo-ve on (see what I did there?) to the primers. You hear a lot of recommendations for Rust-Oleum Filler Primer, but this is another product not found in then UK. Instead, Halfords do a really good line of automotive primers which work really well with print finishing too:


First up, I gave everything a coat of the Filler Primer (in the photo is a smaller can of their Plastic Filler Primer, but I have found their regular Filler Primer works identically in this case and you can get it in larger 500ml cans for only £1 more). It comes in a delightfully putrid orangey yellow colour but sprays on incredibly smoothly and touch dries in 10-15 minutes:


As with the P.38 body filler, I sanded this back down to the base level (sanding wet this time with 400 grit). Even though it's touch dry in 10 mins or so, I leave about an hour before sanding. The colour of the filler primer provides a very helpful contrast between the black PLA and the white P.38, so you can clearly see the small areas it is filling. This is the point all the sanding scratches and print lines are starting to be filled. It may look a mess in but the surfaces now feel very soft and smooth and the patterns created look like they are printed on. I call this the 'Tiger King Stage':


Next, I sprayed a second coat of the yellow filler primer and an hour later repeated the previous step (again wet sanding with 400 grit paper), only this time leaving much more of the primer on the part. This simply removes any roughness and feels more like a gentle scrub. We then end up with each part being super smooth - you can see where all the layer lines, print marks and sanding scratches are, but they are now undetectable by touch alone when running your finger over them:


Finally, everything gets hit with a coat of Halfords standard Grey Primer. Once dry, I just rub everything down lightly with some kitchen roll. For all those absorbent towel geeks out there - Regina Blitz is the shitz. This gets rid of any surface dust that may have embedded itself in the primer when spraying and makes everything as smooth as possible, ready for painting. All layer lines, seams and other print lines are completely gone and the parts no longer feel plasticy as they did straight after printing.


That's all for now. Stay tuned for the next exciting episode where I literally watch paint dry...
Last edited by EctoLabs on August 11th, 2020, 3:03 pm, edited 2 times in total.
cristovalc, mike_waclo, Couture and 3 others liked this
Wow, great work on the filling and priming! I unfortunately got super fed up with the process and missed a couple spots I wished I had more patience for, but your methods really seems to produce a nice smooth finish across the board. I can't wait to see more!

Glad my build could provide some inspiration, as many before me did before I started. :)

PS. If you haven't planned to already, I can't stress enough to pre-thread or re-drill the holes on this. If the screws seem to go in a bit too tight it might end up cracking some of the pieces (doors, the small block wings that the front door pins slide into) and are a pain to fix/re-sand/paint.
cristovalc wrote: May 24th, 2020, 9:42 amI can't stress enough to pre-thread or re-drill the holes on this.
Definitely a good tip. I'm actually further along than I'm making out in the OP and I did make a mental note about your mention of the door cracking. I didn't receive Sean's kit until after most of the parts were painted, but I did test fit everything before the final coat. It all went together pretty well but I still managed to crack the door a bit when inserting one of the set screws. More on that later...
Couture wrote:Looking good. I'm gearing up for my own build with the same kit, just dreading the filling/sanding process.
Yeah, it's never the most enjoyable part of a build but it is worth spending the time doing it properly if you want a really good finish. Luckily, most of the parts have nice flat surfaces so it's not too bad. You could spend even longer working your way through different sandpaper grits but I didn't see the point in this case. I would recommend avoiding getting too much Bondo/P.38 in the pre-made holes or on parts that have a lot of grooves such as the vector plates and knobs or you'll be spending an eternity digging out solidified filler with a blunt instrument.
Welcome back guys and gals to another exciting instalment of The Correct Way of Spending Your Days During Lockdown. So... we have all the trap parts primed, which mean's it's paintin' time. So, in the words of the ledgendary Bob Ross - "Let's get crazy!"

First up - my weapons of choice. As I mentioned previously - here in the UK, Halfords do a great line of paints and primers and their Matt Black spray will be perfect for the final finish. I'm also using a couple of Rust-Oleum sprays - Elegant Finish Silver for the undercoat and Painters Touch Cherry Red Gloss for the side rods:


Thinking ahead to weathering the trap, I am not a big fan of using silver paint or a marker to draw over the topcoat. I just don't think it looks all that convincing. Instead, I'm adding a silver undercoat. Then, later on, lightly scratch off small lines of the black topcoat to reveal the metallic colour underneath - effectively mimicking the effect you would get from scratched paintwork on real aluminium.


Now the silver coat is on, everything starts to look far more like metal. There's a few print lines on one of the doors that I could have smoothed out a little better but these should largely be hidden once finished, so I pretended to not be annoyed by it and moved on. It is at this point that I suddenly realised I had forgotten about the welding effect I wanted to apply to the rear box to mimic the look of the GB1 hero trap. It's not too late to sort it out at this point so I used some black Milliput epoxy putty to mould a 'weld line' around the base of the box:


The Milliput takes a few hours to fully harden, but once ready, it's time for the first coat of matt black:


While looking at the reference pictures of the GB1 hero trap, I realised there was also some welding where the handle meets the frame so I used the Milliput technique in this area too for a touch more accuracy:


Everything else is then given the matt black treatment. I forgot to take a photo here, but I'm sure you get the idea...

Listen! Do you smell something? It must be the postman... Hooray the mega-deluxe kit from Sean Charlesworth has finally arrived from California!! Ooh, a lovely big box full of goodies. This includes the authentic components such as the CAL-R resistor, pedal relay, foster connectors, Hammond boxes, knobs, switches, aluminium and faux-metal side plates, as well as various electronics like the air pump for smoke and servo mechanism for the doors. You can grab these kits for yourself from Sean's Etsy store here:

https://www.etsy.com/uk/listing/8009689 ... it-combine
https://www.etsy.com/uk/listing/5811769 ... hanics-kit


I also ordered one of Sean's real aluminium vector plates for the side of the trap as I figured it would be hard to get the 3D printed equivalent looking anywhere near as good. Unfortunately, the holes are not pre-drilled so I used the printed version to mark where the holes need to be on the back of the plate. Aaaaand... right on cue... my electric drill decides to stop working. Bollocks. Ah well, improvisation has got me out of a few scrapes in the past so, armed with my clamp wrench (easily the most useful tool I've ever bought), I clamp in a drill bit, gaffer tape the plate to a plank of wood and start drilling through the plate by hand:


I didn't expect this to work, but I was able to grind through the metal quite easily and create the holes needed without too much bother. I then flipped the plate over and used a larger drill bit to create the countersinks from the front. In the end, I ended up with the finished plate and at the cost of only a sore wrist and a red palm. I'll let you insert your own joke here.


Sean ships an accurate MC250 CAL-R resistor but this needs the wings flattened slightly to fit between the grooves of the vector plate. Luckily, the resistor has an aluminium body so a hand file does the job - I would recommend going slowly on this, checking the fit every few seconds:


With the vector plate done, it was time to fit out both side panels. I painted the two rods red and attached them along with Sean's faux-metal side plates. These are made of plastic but really do look like real polished metal, even in close-up. The teardrop knob is actually one of the 3D printed parts that had a lot of visible layer 'stepping' on the top and the skirt , but has come out pleasingly well after the filling and priming. Just need to add the white line. Finally, added some vinyl labels from demon-vice-commander (https://www.deviantart.com/demon-vice-c ... -373970837) and things are really starting to come together:


Wheels on. Front faux-metal plate test fitted...


And hazard stripes added to the doors. Rather than painting these one, I used two layers of 19mm yellow electrical tape (as it was done on the hero trap) and cut the excess with a knife:


Unfortunately, the only component of note not included in the kit is the brass Legris banjo that sits on top of one of the pedal's Hammond boxes. I guess these are much harder to source, so I'll try and do my best with a 3D printed replica. This I printed at a higher resolution to lessen the layer lines as much as possible and to avoid the horrors of Bondo:


And then, with a bit of priming , sanding, and painting magic...


Voila! A lovely colour match along side the real brass foster connector I think. As you can see, I went ahead and followed the guide to create the GB1 style hose...

...but more of that next time when I start the assembly and make a ridiculous amount cable spaghetti.
Last edited by EctoLabs on August 11th, 2020, 3:11 pm, edited 2 times in total.
tobycj, Kingpin liked this
Coming together real nice! Love that deep black you got out of it and how smooth everything is. I might hit you up later on your technique for the weld lines once I get going on my proton pack.

I also want to give a shout out to Halfords on their gorgeous spray can design! Super jealous of those truthfully.
Aaaaand we're back with the next fun-packed episode of Rinsing Through Your Furlough Like A Boss...

All the parts are now nicely painted, so it's time to move on to the guts of the trap. I downloaded Sean's Electro-Mechanics's guide PDF from his Etsy store which is based around a shopping list of additional electronics not included in his kit. For simplicity's sake, I went with almost all of these recommended components with the exception of the main lighting. I'm mainly using Adafruit stuff here which in the UK can be ordered from Mouser.com - they ship from their warehouse in the US, but still manage to deliver (for free) in only 3 days.

The main microcontroller is the Metro - Adafruit's Arduino Uno clone:


For the smoke, I'm using 2x Joyetech eRoll Mac eCigs with a vape mixture of 80% vegetable glycerine, 20% deionised water:


Wiring everything together was straightforward but took a while, eventually producing a mess of multicoloured wires. Along with the kit items, I'm using the Adafruit Music Maker Shield for SFX playback, 2x Adafruit 3W Enclosed Speakers, Adafruit Bi-Color Bargraph (can display red, green and yellow), RS Li-Ion Battery (3.7V, 5.2Ah) and an Adafruit PowerBoost 1000 Charger (which converts the 3.7V battery power into a 5V circuit and also makes it easy to recharge the battery via micro USB):


The main lighting effects are where I deviated slightly. Instead of using three individual white LEDs and a lighting gel, I opted to use 3x NeoPixel Jewels. These are roughly the same size as the white lights that Sean used, only each Jewel contains seven 5mm NeoPixels - and each NeoPixel contains one red, one green, one blue and one 6000K cool white LED. This gives us a total of 21 pixels that can be controlled individually for lots of cool effects and pretty colours. They are also really bright which is great for the blinding effects of accidentally looking into the trap.

The great thing about the Jewels is that they can be linked together in a chain, so we only need to use one data pin on the Arduino. I created this chain with a 3-pin JST connector - the data wire connects to a digital PWM pin on the Arduino board, and also has a 470 Ohm resistor soldered inline near the first Jewel which protects the first pixel in the chain.

I also needed to modify the design of the LED mount to fit the Jewels. With my design the soldered wires can be fed into the centre of the mount and only needs a single small screw to secure in place. If anyone would like the STL for this, you can grab it from here: https://www.thingiverse.com/thing:4426034


Right, let's finally start putting this all together. The LED mounts are attached to the top section in between the speakers. As I am not using the supplied lighting gel, I cut a strip from a clear plastic document wallet instead which is sandwiched between the lighting and speaker assembly and the mesh from the kit. Leaving the plastic out completely creates a cleaner look, but I figured it would be wise to have a barrier between the smoke holes and the electronics so vape residue (which is horribly sticky from the glycerine) cannot settle on them over time:


Then, I focused on the door mechanism which is, quite frankly a work of genius. Working out a way of fitting two servo motors and a chain system as well as the bargraph and separate LED into such a small and irregularly shaped area is no mean feat, but this really works incredibly well. Fitting the small plastic chains around the axels was extremely fiddly as there's not much room for manoeuvre and the links can easy unclip themselves. A number of attempts and many unrepeatable expletives later...


Even with all that packed into the front section of the trap, there's still just enough room for the 16 (count them!) wires attached to the bargraph and yellow LED. I sanded the underside of the bargraph plate and used a load of hot melt glue to keep everything in place:


Next, I assembled the rest of the main body until all electronic components were in place, leaving off just the side panels. The doors slide into place easily, but as Cristoval pointed out in his build, it is easy to split the ends of the door panels if the threads are not carefully pre-threaded. The two socket screws at the rear ends went in fine, but I still managed to crack the plastic on one of them when inserting the mini set screws that tighten against the metal axels (I should have dug out some of the plastic in advance). I repaired this with some super glue and used set screws on both sides of each door to secure.

I'm not gonna lie - as a bit of a neat freak when it comes to cabling, this rats nest is making me rather anxious. Nevertheless, it's all starting to look like a proper ghost trap... albeit a disemboweled one:


Now it's time for the re-programming. As I mentioned in the first post, I want to edit the code to make the trap behave and sound a little more like the Sedgewick trap from GB1. With Jeremy Williams' original code, the first stomp on the pedal opens the doors and produces smoke, flashing lights and sound all at the same time. The second stomp closes the doors immediately, illuminates the bargraph and starts the red light blink and beeping. The SFX are also taken from the Video Game files that were released a few years ago and don't sound much like the movie so I want to try and recreate the sound where possible. I want something more accurate, namely:

* STARTUP WHEN SWITCH IS FLICKED ON - Need to improvise on this one, but want to replace the default sine tone with a cooler sound effect)
* FIRST PEDAL STOMP - Doors open with pinkish white light and door opening sound effect. The trap should be still and relatively quiet in its open position until the second pedal stomp as it is in GB1.
* SECOND PEDAL STOMP - Lights and sound intensify and capture sequence begins, mimicking sucking a ghost into the trap => Doors close once capture is complete => A few seconds of silence => Bargraph illuminates with an accurate sound effect => Red light blinks with more accurate beep => Blue electrical spark effect to mimic Venkman's nudge => Smoke begins to pour out of the trap.

...not too much to ask for right?

Let's get it jacked up to the computer and give it some balls! Find out how I do next time...


Last edited by EctoLabs on August 11th, 2020, 3:17 pm, edited 1 time in total.
How did you fare with the programming? I bought some neopixel jewels too, but I see that neopixels and servos conflict with each other in the same sketch unless you adopt a different library, which also requires wiring things differently than the instructions when using an Uno. I'm currently trying to figure out why my servos are going bonkers. They work okay when I run a servo test program, or when I edit the sound FX commands out of the trap code, but go haywire in the normal program. Maybe my mp3 shield is faulty.
Nuclearjungle wrote: August 11th, 2020, 7:40 am How did you fare with the programming? I bought some neopixel jewels too, but I see that neopixels and servos conflict with each other in the same sketch unless you adopt a different library, which also requires wiring things differently than the instructions when using an Uno. I'm currently trying to figure out why my servos are going bonkers. They work okay when I run a servo test program, or when I edit the sound FX commands out of the trap code, but go haywire in the normal program. Maybe my mp3 shield is faulty.

I've been meaning to update this thread for ages but been a bit busy. Yes, I spent quite a bit of time editing the code and did manage to tame the servos but I couldn't get the alternate library working at all, even when I moved the servos to the required pins.

I realised though that there was no need for the servos to be attached to the code while the lighting effects are running, so I reverted to stuck the standard library and called a servo.detach() as soon as the doors are finished opening. This means that the neopixel library can't interfere with them during the main sequences. I then only reattach the servos to the code just before needing to close the doors.

I'll update this thread properly asap and share the code I am running. Hope that makes some kind of sense!
Nuclearjungle liked this
Interesting. I'm going to try to fix my servo problem this weekend, and then start worrying about the neopixels. I might as well attempt to figure out the alternate servo library (even though I haven't heard of anyone getting it to work so far), but I'd definitely be interested in seeing what you came up with in terms of code.
You mentioned managing to tame the servos; was that only because of the neopixel conflict, or were they misbehaving for any additional reasons?

At this point, I've tested pretty much everything and replaced all the major parts, and the servos still don't behave correctly. The only things that made a difference at all were the new servos from Adafruit, which are upgraded to MG90D instead of MG90S.
Nuclearjungle wrote: August 22nd, 2020, 12:44 pm You mentioned managing to tame the servos; was that only because of the neopixel conflict, or were they misbehaving for any additional reasons?

At this point, I've tested pretty much everything and replaced all the major parts, and the servos still don't behave correctly. The only things that made a difference at all were the new servos from Adafruit, which are upgraded to MG90D instead of MG90S.

Yes, it was just the NeoPixel conflict that was the issue. I used the two MG90S servos that Sean shipped with his kit. They didn't misbehave that much really - just some fast twitching whenever the lighting effects kicked in. They were still at other times. Here's the Arduino code that I wrote for my trap. I changed it a fair bit from the original and some of it is specific to my setup, but maybe it can be of some help to you.

http://www.ectolabs.net/files/CD_Ghost_ ... .0.ino.zip

If you look at the sections relevant to the doors, you'll see I created a reusable function 'trapDoors()' to which you pass the parameter 'open' or 'close'. Once called, it attaches the servos, updates their position and then detaches them after a delay of about 300ms. This way, they are only actually active in the code for a very short amount of time and are effectively dead while the NeoPixels do their thing.

There is also the parameter 'calibrate' which I run at startup - this makes sure the doors are in the correct starting position when the trap is switched on. I think I played around with the opened and closed values as they weren't finishing in a symmetrical position to start with.

The code is commented fairly well, so hope it's not too confusing!
Nuclearjungle liked this
Thanks! After spending all day yesterday tearing my electronics apart and testing everything, I eventually concluded scientifically that my components were assembled on an ancient Indian burial ground, and therefore cursed. But then I saw your code posted today, and I immediately got to work rewiring things and uploading your code. You did an amazing job on the new sequence, and my servos seem to work properly now! I only have one small issue now that I need to figure out: I seem to be having some slight trouble triggering the trap now. I'm just using the rotary switch at this point, but if I give it 2 clicks like before, it opens and then immediately shuts and silently aborts the whole sequence. If I leave it "pressed" for a second until it proceeds to the capturing/closing phase and then give it the second click, I see the whole sequence as intended, but I can't get it to just stay in the "open" phase while waiting for a second stomp. Maybe I have something wired incorrectly somehow. Still, though, everything is looking infinitely better now with your code. Again, great job!

EDIT: Nevermind, I noticed that it stays open while the sound is playing, and you need a long sound to keep it open. You saved the day, man.
Ah, great to hear that sorted it. I wouldn't have expected it to run properly on another trap. Regarding the rotary switch, I didn't like using 7 positions when you need to do a 'double click' each time as it made it to easy to overshoot and do three clicks by mistake. I moved the stopper so you can only move it by two positions each way. That way you can turn it back and forth quickly without needing to be careful.

I also changed the sequences to behave more like the Sedgewick trap - first stomp opens the trap and remains in a primed state ready for capture; second stomp starts the capture sequence and automatically closes the doors over the ghost is inside. This will only work properly if you use the new sound files I made as the sequences are timed specifically with them. I made them as close as possible to the sounds heard in GB1 rather than the video game.

I would like to share those with everyone, so I'll try and get them together and update this thread today if I get the time. Bear with me....
Yeah, I was using the original video game sounds as placeholders with your code, but the original code used a short "trap open" sound followed by a looping sound, so it was the shortness of the "open" sound that made it quickly abort. I temporarily switched it to the extended red light beep for testing, which made everything work great. And fortunately, I had already bought some neopixel jewels.
    Soundtrack for GB 2020?

    I don't get the whole rap/hip-hop complaint. I mea[…]

    I think the opening will be in the past. Some min[…]

    So, both on Facebook and over at the RPF, there ar[…]

    Nice in detail review. Thank you. What is consid[…]