Project Mini-Me Fire Breather

March at Intrigued is slowly turning into October junior. This isn’t by any divine strategy (although a spring Halloween would be awesome!). Nope, this is entirely due to looking at my post queue and realizing I need to get my ass in gear and get at least LAST year’s Halloween related posts out. If not, it pretty much snowballs from there as the prop building is already in progress for this year’s event and before you know it I’ll be in full stress mode trying to get everything planned for the big event. How the hell did I get all this done when I was still working!?!

Whining about it, isn’t going to solve the problem, so let’s get to work. Today’s featured Halloween prop is another “upgrade” project.

Our Mini-Me dragon started out as a base prop that one of my nephews or nieces gave me for Christmas. Note to others, if there is ever a need for a gift idea, you can never go wrong in the haunt department. I picked up the daddy dragon the year before at Big Lots (will show that later). It was a more featured offering with lights in the eyes, moving mouth and various dragon related sounds. The Mini-Me version looked similar, but was lacking these additional features.

Hit the jump to see how this store-bought prop underwent a dramatic improvement before heading out to the haunted trail.

Now, this prop is nice on its own, but clearly we could step up its cred if we could maybe add one or more of the features found in the larger model. Brought it up to the den to assess the possibilities. Like many of the props I’ve been acquiring lately, it was put together surprisingly well. Strong plastic sub-assemblies held together by screws. It also looked like the head would separate easily adding to the hope there was room in there to add some circuitry.

You can see the separation between the upper skull part and then the lower jaw is already hinged – you could push it down with your finger and it would snap back to closed. There were also a large number of screws which implied the pieces were hollow. All things were looking good.

Grabbed a screwdriver and started removing screws – the top portion with up of two halves first. To say I was shocked at what I found inside would be an understatement. Apparently it was already designed for the additional features, but either the makers decided it wasn’t worth the investment or there were higher priced lines they were marketing and reusing the frame was cost effective. As you can see from the shot below, the head was hollow with plenty of room to install LEDs into the eye cavities.

Now let’s take a look at the structure underneath this top skull. Not only did it already have a speaker area carved out, there was a bar pivot system that allowed the jaw to move. They added the basic spring wire tension to pull the mouth back up if it was manually lowered – it even had a lever system (see top of white lever attached to the bar just right of center). Press down on that lever, lower jaw would open, let it go, lower jaw closed. Ladies and gentleman, our planned work just got a whole lot easier.

I tackled the sound part first. Since there was already a cavity there, complete with holes to allow it to pass through better, I simply modeled a new insert in Fusion 360 that would hold a small speaker and fit perfectly inside the existing compartment – note, I even added the bump outs (look close at the inner part of the ring). Left a small hole to let the wires out and sent it to my 3D printer. An hour later, the wires were added, the speaker was glued to the inside of the insert and then hot glued into the expected location. A slot was cut in the back of the head to let the wires pass through – had a design change regarding that we’ll cover in a bit.

Next big task was to deal with jaw movement. There is no shortage of servos in the Intrigued lab. We’ve been focusing on adding a lot of movement to our haunted trail for several years now and servos have pretty much taken over the role of the heavy duty wiper motors we used to use. The servos pretty much run on 6 to 9V where the wipers were based on a 12V configuration which put a heavy drain on our power routes. Since this project only required moving a small/lightweight lever, went with the MG90S Mini. Very compact and would fit into the available compartment nicely.

Went ahead and whipped up a servo holder in Fusion 360 and printed it out on the 3D printer. There were already tabs in the skeleton for whatever mechanism they used in their other model. Simply filled up the extra compartment space allowing the servo to be held in place by the same tabs. The critical piece was making sure the servo arm was positioned so the 90 degree range of the servo would allow it to pull down on the jaw lever. The old tension spring was not technically needed anymore, but left it in just to take the pressure off the servo when it pulled the jaw back. Used a piece of wire to connect that arm to the lever and presto, moveable jaw!

I mentioned a design change earlier. It was obvious it was going to need 2 wires for the speaker, 3 wires for the servo and another 2 wires for the eye lights (latter of which still needed to be put in). Rather than waste the wire to run all those individually, grabbed some ethernet wire and used 7 of those 4 twisted pairs to power the various components. Pretty much use JST connectors (2 and 3 pin) exclusively these days – they fit tight, keyed so they only go in the proper way and splicing into the wire leads is a LOT easier than messing with the pin in Molex versions. Be sure and label those connectors!

Now there is just one cord to snake back to our proprietary prop controller that is powered by a Arduino NANO to move the servo and turn on both the eye lights and various sound clips using a DFPlayer-Mini board.  Wasn’t planning on swapping out the internal components in the skull and thus just wired those directly into each of the components without connectors – note the wires going to the top of the head where the eye lights were now installed.

Admittedly a bit pressed for time, so just brought the single ethernet cord out the back of the head. If I have time this year, I’ll probably take all the screws out of the spine and try to lay the cord in the middle to make it a little cleaner. Honestly, the extra wire isn’t really noticeable in the dark.

Here is the front shot with the top of the skull now attached.

Okay, now for the second design change. When I had the top of the skull off I noticed there was a hole in the structure that point out into the throat area. That is when it hit me – the daddy dragon had a light in there to give the impression it was breathing fire. How realistic is a dragon prop that doesn’t breathe fire!?! Quickly set about taking the head back apart. Grabbed a couple of red LEDs, slapped resistors on their positive leads and hooked them into the existing eye circuit. Carefully glued the new LEDs into the existing “throat” holes before hooking everything back up. Test triggered the sensor – we now have a fire breathing Mini-Me dragon!

Here is a shot of our new Mini-Me Dragon out on the trail. As you can tell, the daddy looks exactly like the new prop, just around three times bigger.

Here is a shot to give you a feel for the larger dragon at night. It is hit with a UV light to give it that extra spooky kick.

… and now our Mini-Me version gets to join in the haunting fun.

Hope you enjoyed this run-through on one of the new additions to last year’s Haunted Trail of Tears. Even if you do not go full out with the sound and movement, just doing something relatively easy like adding lights to an existing prop will give it that extra finish for your guests.

Stay Calm and Haunt On!