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Thermal Detonator

by RoelVeldhuyzen Jan 26, 2017
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hey im making one of these right now just had a quick question. What type of resistors did you use?

I believe I used 220 Ohm resistors here, but I'm not 100% sure on that.

I love making these! I'm not big on wiring so I glued in a little led and for the bulbs a quick wipe of clear silicone did the trick. For the red light...a red clear lego piece. No wiring needed. it doesn't turn on externally but to me thats not that big of an issue.

Hi, wonderful model! I am printing it now on my Elegoo Mars, comes out great. One question though - you write that the holes should accommodate 3mm and 1.8mm LEDs, but on my print the holes on the bottom half are 4mm wide, and my 3mm LEDs slip right through. Is that a mistake in the description? Or am I printing it wrong?

Hi, thanks for your comment. You are absolutely right, the LED measurements should be 3 and 5mm, not 1.8 and 3! I can't believe it took this long for someone to notice the mistake in the description.
I can only imagine the print looks great in resin, but keep in mind that the files are designed with FDM printer tolerances/clearances in mind and the holes should be quite tight to friction fit the LEDs, so some sanding might be needed to get the correct size LEDs to fit in a resin print :)

I've built one of these exactly as described, but the sketch doesn't run when connected to a 9V battery. It works fine when connected via USB to my computer. Any ideas?

Heres my Sketch and the wireing diagram for those who want something different. You can use a Arduino nano and a 9V battery. Have fun improving and trying.

const int c = 261;
const int d = 294;
const int e = 329;
const int f = 349;
const int g = 391;
const int gS = 415;
const int a = 440;
const int aS = 455;
const int b = 466;
const int cH = 523;
const int cSH = 554;
const int dH = 587;
const int dSH = 622;
const int eH = 659;
const int fH = 698;
const int fSH = 740;
const int gH = 784;
const int gSH = 830;
const int aH = 880;

const int buzzerPin = 8;
const int ledPin1 = 12;
const int ledPin2 = 13;
const int ledPin3 = 11;
int counter = 0;

void setup()
//Setup pin modes
pinMode(buzzerPin, OUTPUT);
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);
pinMode (ledPin3, OUTPUT);

void loop()

digitalWrite(ledPin3, HIGH);

//Play first section


//Play second section

//Variant 1
beep(f, 250);
beep(gS, 500);
beep(f, 350);
beep(a, 125);
beep(cH, 500);
beep(a, 375);
beep(cH, 125);
beep(eH, 650);


//Repeat second section

//Variant 2
beep(f, 250);
beep(gS, 500);
beep(f, 375);
beep(cH, 125);
beep(a, 500);
beep(f, 375);
beep(cH, 125);
beep(a, 650);


void beep(int note, int duration)
//Play tone on buzzerPin
tone(buzzerPin, note, duration);

//Play different LED depending on value of 'counter'
if(counter % 2 == 0)
digitalWrite(ledPin1, HIGH);
digitalWrite(ledPin1, LOW);
digitalWrite(ledPin2, HIGH);
digitalWrite(ledPin2, LOW);

//Stop tone on buzzerPin


//Increment counter

void firstSection()
beep(a, 500);
beep(a, 500);
beep(a, 500);
beep(f, 350);
beep(cH, 150);
beep(a, 500);
beep(f, 350);
beep(cH, 150);
beep(a, 650);


beep(eH, 500);
beep(eH, 500);
beep(eH, 500);
beep(fH, 350);
beep(cH, 150);
beep(gS, 500);
beep(f, 350);
beep(cH, 150);
beep(a, 650);


void secondSection()
beep(aH, 500);
beep(a, 300);
beep(a, 150);
beep(aH, 500);
beep(gSH, 325);
beep(gH, 175);
beep(fSH, 125);
beep(fH, 125);
beep(fSH, 250);


beep(aS, 250);
beep(dSH, 500);
beep(dH, 325);
beep(cSH, 175);
beep(cH, 125);
beep(b, 125);
beep(cH, 250);


Is it possible for you or anyone to post a circuit diagram?

Sure thing, I added one to the image gallery. It shows an Arduino Uno since that's all the tinkercad tool has to play with, but it obviously works the same way with any arduino you can fit in the print :)
The diagram shows resistors between the LEDs and the board since that is the best practice, but most LEDs will be fine without one in this setup.

Did you use translucent filament for the switch?

Not for the Switch, I did swap out the (red) LED cover with clear resin cap to diffuse the light a bit better.

I'v got Anycubic i3 Mega & Cura 15 and I'm not sure in which direction the parts should be printed for best results?

On any FDM/FFF printer the files should be rotated 90º from what they are in the images above. (I'll see if I can rotate the files at some point).
So the half spheres should have the largest part of them flat on the bed so the outside of the sphere prints as smooth as possible, you should need little or no support on the inside depending on how fine tuned your printer/material is.
The switch should have the top (with the little nubs) facing upward and it requires support to print correctly. the LED cover can be printed both with the flat face on the bed, or with the four legs on the bed, depending on your own preference.
Good luck!

Thanks a lot for your advice - the prints are very good.

Glad to hear it. Feel free to share your results with the rest of us if you feel like it. It's always fun and inspiring to see other peoples prints :)

Whats the best switch to use for this? and leds....link to maybe aliexpress parts

I initially used a mini push button switch, one of those four pin ones people mostly associate with breadboards. That worked fine, but the the range was a bit too small for my liking and it was a bit too stiff too.
So I switched to a simple spring and metal plate set up. Think what you find in a battery case. I soldered one wire to the spring and hot glued that to the top half of the dome. Soldered a wire to a coper plate and hot glued that to the bottom of the sliding switch. When they make contact the Arduino turns on. The range is a lot more forgiving now.

As for LEDs, anything with the right size and voltage rating should work.

Hi Roel, thanks for the print. How do the two halves stick together? I don't see a locking mechanism?

It friction fits into place. The two pieces should slide over each other tightly, making it impossible for them to accidentally fall apart.

Do you have a link to the STL of the stand in the picture?

Sure thing, I just added the file :)

What is the best way to print this?

so whenever i try to import the switch and lightcap into cura, it says can not load stl.
any help??

It works fine here, even when I re-download the files. older/newer version of Cura maybe?
Can you load them into Netfabb? If so, does exporting them to new STLs help?

dude honestly thank you

also, im not the best at wiring and stuff so if there is a picture i could use that would be great :)

Okay, I added a photo of my wiring, it's difficult to see, but I'll try and explain what you see. (here is a hi res version: https://tweakers.net/ext/f/g9txAz0Nt84JK5C6PfMRJ8NK/full.jpg ).

1, 2 and 3 are the positive leads of the yellow LEDs, 4 is the positive lead of the red LED. 5 are the negative leads of the all the LEDs, connected together to save space (you can see the leads soldered together in the top pic).
So 1-4 are connected to the Arduino pins that are mentioned in the code. 5 is connected to a Ground on the arduino.
6 is the positive lead coming from the battery, and goes to the power input on the arduino. 7.1 is negative going from battery to the spring on the switch. 7.2 goes from the other part of the makeshift switch to the power on the arduino. (you could, and probably should switch those two around, interrupt the + between battery and arduino instead of the - lead.
That's all there is to it.

Finished one using the same arduino nano to produce sound as well. Also edited the light transitions. https://www.instagram.com/p/BZ6Ipa3AHdN/

Could you share the code for the sound?

Is there a site for the wiring and code for sound?

It's not too difficult to add some sound ;-) I'm working on making one of these now. https://www.instagram.com/p/BZ3NziDAZXI/

AS an Arduino beginner it is not easy to add sound. Got the Sketch for the LEDs working and a second sketch for making a sound on a passive piezo buzzer. But I am not abled to combine those two. Any hints how you did it?

Are you trying to use a delay? You need to be able to control the lights and buzzer all at the same time. You can try this for some tips on how to avoid a delay: https://learn.adafruit.com/multi-tasking-the-arduino-part-1/ditch-the-delay

Yeah, thanks. Inam beyond that now. You are right, you have to get rid of the delay. I Used a time machine. Still figureing out the right timing of the LEDs. My result is not perfect, but it learning is in progress.

  • Posted with 3D Geeks Thingiverse Browser App

Oh, you can play sounds directly from the Arduino, no need for a sound board? That makes it easier to fit than I though. I'll need to look into this :P

Beautiful model, works great on the Form 2.

Man, that Form 2 is something.. And great job on that paint job! :)

Roel, How did you paint it? awesome job!

Steve, It was all done with an airbrush using Alclad paints. Multiple full layers with toothpaste applied after each color to get the random chipped paint effect.
I did a write up here: https://www.starwarsawakens.nl/artikelen/roels-replicas-thermal-detonator/ But it is in Dutch, sorry about that. I'm working on a manual translation (the auto translation might help you a bit, but it's not the best :P ). The photo's might be helpful, though :)

new to 3d printing, but should I print the files as they are set up now, or do I need to lay them flat on the bed? do i need rafts or supports?

The orientation depends on the slicer you use, some import them in different orientations, but they should be layed flat on the bed. Standing up like in the Thingyverse renders won't work.
You definitely want support for the top half, it has pieces that don't touch the print bed, and you might want some support in the middle of both domes (around the switch hole, for the top dome).
Good luck :)

Do you have a wiring guide?

This is how my wiring is set up. First time doing any electronics since school so may not be the best but it's working in my detonator. https://www.dropbox.com/s/nsewlf0v870odk3/Thermal%20det%20wiring.jpg?dl=0

That's exactly how I did it :)
I'm also no expert at electronics, but it seems to work fine.

Hi, what kind of switch is used in that awesome Build?
All the other parts are ordered

There is one of those standard breadboard switches in there now (https://i1.wp.com/volthauslab.com/wp-content/uploads/2016/09/btns.jpg). With a rubberish button top so it has a little bit of wiggle room. But the switch hast to be pushed all the way back and stay there for it to work.
On further reflecting I think it might be best to put a small spring and metal plate in there, like those in battery holders.
Spring on the housing, plate on the sliding switch, when they touch you complete the circuit. no switch required. That might give it a lot more leeway, is easier to stick into place and is very simple to set up.

thank you for the asnwer. i like your idea. will try it in my build.

Great, good luck. Let us know how it turned out, I would love to see the final result :)

Roel, do you think it would be possible to get a Bill of Materials in terms of the electronics? I know you mentioned the arduino nano, the LEDS and 9volt. But specifically what kind of switch was used. Can you open it up and take a few photos?


There is one of those standard breadboard switches in there now (https://i1.wp.com/volthauslab.com/wp-content/uploads/2016/09/btns.jpg). With a rubberish button top so it has a little bit of wiggle room. But the switch hast to be pushed all the way back and stay there for it to work.
On further reflecting I think it might be best to put a small spring and metal plate in there, like those in battery holders.
Spring on the housing, plate on the sliding switch, when they touch you complete the circuit. no switch required. That might give it a lot more leeway, is easier to stick into place and is very simple to set up.

Beautiful project! Is it possible to upload the code for community use with this build?

Good idea. I just added the (very simple) Arduino code to make the LEDs blink :)

What kind of electronics are inside?

There is an Arduino Nano in there. With a 9v battery and the 4 LEDs.
The nano runs a few lines of code that make the orange LEDs blink in the right sequence.

Any chance of seeing the inside of this beautiful build?

Thats awesome! so now you could build in a small beeper/speaker to make the noise!

Adding sound is a back burner project. Don't know how to do that yet. But I will at some point in the near future :)

any update on adding the sounds?

Ditto on the sounds update progress? Or did adding sounds fall off the back burner? LOL

To be honest it did kind of fall off my radar due to other projects and the fact that if I want to do it right I need to completely redesign the power management. Simply cutting off the power to turn it off won't do if it needs to play a specific sound as it turns off. Turning it on and playing sound is easy enough (as long as I can find components small enough), but that shut off sound kind of stumped me back then.
I think I will bump it up on my to-do list, though. Might have a look at it again in the future.
I did see other people who found solutions for audio over the past few years, though.