Finally at the point where I can share this. Back in November I decided to improve on my CAD skills by trying to replicate Holtzmann's remote trigger armband prop. If you don't recall, this is what she uses to trigger the release of the trap pedal, it ejects the pedal across the stage during the concert scene. She later uses it to trigger the release of her two pistols from the sides of her pack.
Unfortunately there's not a lot of good reference for this. At least one stunt version was auctioned, there's photos (with helpful measurements) in the Reference Library here:
https://www.theghostbustersreferencelib ... ton-pistol
These are missing a lot of detail, you'll notice that the batteries, switches, bolts are all fake. So I eventually gave up and just grabbed screenshots from the 4K Blu-Ray film (Extended Edition, not that it helped much).
The clearest shot is the suiting up scene in front of the Ecto:
![Image]()
The prop also changes a lot throughout the film, by the time Holtzmann gets on stage at the concert it's already been repaired with hotglue and electrical tape:
![Image]()
Anyway, after painstakingly extrapolating measurements from the screenshots and as many angles as I could find, while checking against the stunt replica to see if they'd help with the details, I came up with this:
![Image]()
![Image]()
And here's our Holtzmann from the South Australia Ghostbusters testing the first prototype earlier this year:
![Image]()
(It's unpainted and has no wires yet).
If you'd like the 3D files (for strictly non-commercial use) they're available for free here:
https://www.printables.com/model/123031 ... te-trigger
and here:
https://makerworld.com/en/models/121527 ... te-trigger
In the prototype I made the "screen" a sticker attached to a 3D printed piece, but the plan is to try to backlight this with LEDs. I specifically designed it as a 60x60x5mm screen so I could try laser etching frosted acrylic, but if that doesn't work I could just backlight the sticker.
The top LED above the toggle switches seems to be blue in the film, when Holtzmann flips the switches it changes to green (along with the screen) but I'm 90% sure this was VFX. My ultimate goal would be to use a 5mm RGB LED at the top, and RGB LEDs behind the screen, so that different combinations of switches can change the colour. Perhaps the first switch connects the power, and the second switch changes the LED between blue and green, and the screen from red to green.
NOTE: In the film Holtzmann flips both switches down at once but this seems unnecessary.
I also decided to turn the bulky "knob" on the front into a push button. Not sure what for yet. I don't think we clearly see how Holtzmann ejects the side pistols from her pack (she does seem to use the remote trigger but we don't see it clearly), maybe the toggle switches are for the trap and the push button is for the pistols? Anyway, it moves and supports a PCB tactile switch and a spring mechanism, along with clearance for wiring.
I made sure that the 4xAA battery holder can be easily unscrewed and removed so the batteries can be swapped out as needed, there's not a lot of clearance there.
Finally the side rod seems to just have some metal parts inside it, maybe stacked hex nuts over a bolt or something? I can't tell. So I decided that the side rod would logically act as an antenna, and I designed my own custom piece to go inside it and wrapped it in copper wire. I think it looks good:
![Image]()
![Image]()
So now I've disassembled it and started sanding/priming the pieces. Once that's done I'll hit everything with some satin black paint, prototype the electronics and try to get it installed, then attach all the decorative wires.
I haven't yet designed the separate keypad which attaches to the back of the armband via the ribbon cable, I'm still holding out hope I can find a cheap pre-made PCB for this (they probably scavenged it out of something real) but if not I'll just have to design my own printed version.
Please feel free to share around with anyone who might find this useful, I'd love to see some builds out in the wild! And feedback/suggestions/remixes are most definitely welcome.
Additional Reference Images
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
![Image]()
Unfortunately there's not a lot of good reference for this. At least one stunt version was auctioned, there's photos (with helpful measurements) in the Reference Library here:
https://www.theghostbustersreferencelib ... ton-pistol
These are missing a lot of detail, you'll notice that the batteries, switches, bolts are all fake. So I eventually gave up and just grabbed screenshots from the 4K Blu-Ray film (Extended Edition, not that it helped much).
The clearest shot is the suiting up scene in front of the Ecto:
The prop also changes a lot throughout the film, by the time Holtzmann gets on stage at the concert it's already been repaired with hotglue and electrical tape:
Anyway, after painstakingly extrapolating measurements from the screenshots and as many angles as I could find, while checking against the stunt replica to see if they'd help with the details, I came up with this:
And here's our Holtzmann from the South Australia Ghostbusters testing the first prototype earlier this year:
(It's unpainted and has no wires yet).
If you'd like the 3D files (for strictly non-commercial use) they're available for free here:
https://www.printables.com/model/123031 ... te-trigger
and here:
https://makerworld.com/en/models/121527 ... te-trigger
In the prototype I made the "screen" a sticker attached to a 3D printed piece, but the plan is to try to backlight this with LEDs. I specifically designed it as a 60x60x5mm screen so I could try laser etching frosted acrylic, but if that doesn't work I could just backlight the sticker.
The top LED above the toggle switches seems to be blue in the film, when Holtzmann flips the switches it changes to green (along with the screen) but I'm 90% sure this was VFX. My ultimate goal would be to use a 5mm RGB LED at the top, and RGB LEDs behind the screen, so that different combinations of switches can change the colour. Perhaps the first switch connects the power, and the second switch changes the LED between blue and green, and the screen from red to green.
NOTE: In the film Holtzmann flips both switches down at once but this seems unnecessary.
I also decided to turn the bulky "knob" on the front into a push button. Not sure what for yet. I don't think we clearly see how Holtzmann ejects the side pistols from her pack (she does seem to use the remote trigger but we don't see it clearly), maybe the toggle switches are for the trap and the push button is for the pistols? Anyway, it moves and supports a PCB tactile switch and a spring mechanism, along with clearance for wiring.
I made sure that the 4xAA battery holder can be easily unscrewed and removed so the batteries can be swapped out as needed, there's not a lot of clearance there.
Finally the side rod seems to just have some metal parts inside it, maybe stacked hex nuts over a bolt or something? I can't tell. So I decided that the side rod would logically act as an antenna, and I designed my own custom piece to go inside it and wrapped it in copper wire. I think it looks good:
So now I've disassembled it and started sanding/priming the pieces. Once that's done I'll hit everything with some satin black paint, prototype the electronics and try to get it installed, then attach all the decorative wires.
I haven't yet designed the separate keypad which attaches to the back of the armband via the ribbon cable, I'm still holding out hope I can find a cheap pre-made PCB for this (they probably scavenged it out of something real) but if not I'll just have to design my own printed version.
Please feel free to share around with anyone who might find this useful, I'd love to see some builds out in the wild! And feedback/suggestions/remixes are most definitely welcome.
Additional Reference Images
Statistics: Posted by prodestrian — March 16th, 2025, 4:45 am