Motion Sensing Flasher With SFX




Introduction: Motion Sensing Flasher With SFX

This instructable covers a moderately simply way to put a few electronics gadgets together to make an automated Halloween greeting device, complete with flasher and sound effect box!

For about 2 years I have wanted to put this thing together. Finally, I spent about half of my last Sunday and have it ready to show.

Step 1: Components

I am partial to Electronic Goldmine for various parts ( ). I am not an employee and have no financial relationship other than I have bought various parts from them over the years.

To make this thing, I used 3 main components;

1) Ultrasonic Movement Detector II kit (various sources, various types available).
The one I used has a seperate +/- output trigger for the relays.

2) Sound FX box. I used Electronics Goldmine's "HAPPY HALLOWEEN!" box.

3) Camera Flash Module. ***WARNING: HIGH VOLTAGE, NOT TO PLAY WITH****
Most common flash modules will work, as I routed the activation to a relay. These are NOT to be played with lightly, as they charge up to 100's of volts and have a large current discharge capacity. Mine charge up to 350 Volts

Now that THAT is out of the way....Electronic Goldmine has these as well! Many selections available at their site.

The EXACT components you can use for this may differ. And the EXACT way you connect them may differ. This is just one example and is what I did. For example, you may also use an infrared sensor to detect when people walk up. And, you may have a different SFX that gets triggered. You could also add multiple flashers.

Other components include:
Box or frame to mount parts to. Even a shoe box would work.
Relays (see later)
Wire (a few feet should do)
Electrical tape
Battery connector for 2 AA batteries to flash module.
A few batteries (1 9V, 2 AA's)

And, some tools;
Wire cutter/stripper
Soldering Iron
DMM (for continuity and voltage checks)
Small perf board to mount relays on and wire to.
High Voltage Discharge Tool (see later).

Also, this is a very "quick-and-dirty" method of getting something to work. I may spend more time in the future to design my own ultrasonic sensor, have one power supply instead of each device working on it's own batteries, activate more systems, and all run off a microcontroller that has some specific actions in mind.

But, that is what also makes this project quick, simple and fun!

Now , off to put all these things together, then a short video showing how this thing works!

Step 2: The Build: Mounting Components

So, before you ever work on a project, it's a good idea to have some basic design in mind. Some concept of how you want it to look in the end.

I knew I would want some covering, perhaps a mask, on the outside. And I just happened to have some spare parts to help. I used a small black box, that already had an aluminum strip riveted to the top, so I bent the top to accommodate the motion detector, and mounted everything else inside and on the box.


The motion detector was hot glued to a particle board piece, in turn hot glued to the bent aluminum strip at top.

The sound box was hot glued to the right side.

The Flash module was hot glued to the inside of the front particle board with a rectangle cut in the middle for the flash to shine through. Also, a small hole was cut so the charge lamp could show through!

Step 3: The Build:Wiring It All Together

OK, so now everything has to work together.

The primary tool for this is a simple relay. Again...yep, you guessed it, Electronic Goldmine was my source. I used these 3.38 V relays (but MNFR datasheet showed they are good up to about 12V), and they work fine.

But you could use other similar relays.

First, I simply wired the ultrasonic motion detector's output to both of the relays. At first I tried to use the one + output line only, with the 9V Ground on the relay. This did not work. I didn't spend much time trying to figure out why, save that the 9V ground was not at the same level the trigger output "-" was. So I used the output trigger pair, and the relays started working.

One relay activated the SFX box. The other relay activates the flash module.

The relay for the SFX box is wired to inside of the SFX box, where the rubber conductive button is. One wire was soldered to the + battery terminal (on one side of the button) and the other wire was soldered to the board where the other side of the button would trigger. This was touchy on the top part, as there is only small exposed portion of trace to solder a wire. It took me a few tries, but my soldering skills are not great, and my soldering iron is even worse! To make sure the wires did not pop off....more HOT GLUE!

The relay for the flash module was wired to the flash module wires that activate the flash module.The flash charge lines were shorted to keep the module in continual charge, and a 2 AA battery holder was soldered in place of the 1.5V battery plates. This proved to a very nice improvement to the charge rate, and appears to maximize the flash output. I am not going to detail this for safety reasons. If you already know how these modules work then you are good. Otherwise it is best to stay away from them.

Step 4: IT'S ALIVE!

That's it!

As shown in first picture, the idea is to dress it up as you see fit; A mask, part of a larger display, or even just hiding in the dark by itself somewhere.

I plan to make a foam head frame for my mask to sit on, with the ultrasonic sensors sticking out the eyes, but here a video showing it in action without any covering!


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    10 years ago on Step 4

    Video has 1 flash in the dark at the end....kinda hard to see. My phone does not take the best video...a few frames droped out while shooting. :(


    Reply 10 years ago on Introduction

    Thanks. I have a bag full of flash modules and lots of sensors, so I think I may be doing more of these in the future.