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The Defusable Clock kit is NOW AVAILABLE FOR PURCHASE!


This may look like a dangerous device, but it’s really just an ordinary alarm clock — with a twist.


 

I thought it would be fun to build an alarm clock that looks just like the type of bomb that we always see in Hollywood movies. I certainly don’t know anything about how a real bomb might look, but in the movies they always have sticks of dynamite strapped together, a red digital readout, and a bunch of curly wires. Instead of just building an ordinary clock, I thought it should have a detonation sequence with a scary countdown just like in the movies. And why not make it “defusable” so I an try to stop the countdown by cutting the correct wire?

The Defusable Clock is a fully-functional alarm clock just like you’d expect (a normal beeping alarm, snooze alarm, etc.). But at any time you can press the big red button to start a scary countdown sequence exactly like bombs in Hollywood movies. There are 4 wires across the top of the clock. You have 10 seconds to choose the correct wire to cut: one wire stops the countdown and saves the day, two have no effect, and one will “detonate” the device immediately. These role of each wire is randomly assigned when the detonate button is pressed, so it’s a new challenge every time. Also, the wires are attached with screw terminals, so you can replace them easily. If you don’t want to actually cut the wires, you can just pull them out of the screw terminals if you keep the screws a little loose.

The microcontroller is an ATmega328 with the Arduino bootloader, so this clock is programmable with the Arduino IDE. The ATmega328 is certainly more powerful than needed for a clock, but this device has lots of inputs/outputs, and ATmega328 chips are now about the same price as the older ATmega168. It keeps very accurate time and requires a simple 9V “wall wart” power adapter. A special alarm mode lets you even use the countdown sequence as the alarm and require it to be defused when you wake up in the morning. What a stressful way to start the day!

We are going to offer this as an electronics kit later this fall. Only the electronics will be in the kit — nothing that looks like dangerous explosives! With some imagination, I’m sure you can make a great looking Defusable Clock for yourself, but don’t go scaring anyone with it, and don’t bring it anywhere near an airport, ok? The product page will have plenty of warnings not to use this kit for any evil purposes or get into trouble with your school, employer, or local law enforcement! There will also be a picture gallery where you can submit a picture of your clock after you build it.

UPDATE: the Defusable Clock kit is NOW AVAILABLE FOR PURCHASE!

I’m sure some of you will have some ideas and comments, so please leave them below. Keep in mind that this is no more dangerous than any other alarm clock, and yes, we have already spoken to a lawyer about all of this.

Here’s one more version I made using clay for plastic explosives:

I recently had the idea of printing a PCB design on a t-shirt. Since I don’t do my own silkscreening, I just wanted to upload my EAGLE PCB design to a custom t-shirt provider and have them do the hard part. In this post I’ll show you how you can do the same for your favorite board design. Mine turned out great!

 

First, I exported my board design from EAGLE by choosing File -> Export, then picking Image from the next menu. You want your image to be high resolution, so increase the DPI value to at least 400 to give you a large image. Choose a file location for your large PNG file.

 

I then used Custom Ink to have the t-shirt made. I chose a black short sleeve Hanes Beefy-T. The shirt design tool makes it easy to upload an artwork image. After uploading, it asks you to choose the colors that are in the image. My standard Eagle board image has red, blue, white, green, and yellow. The colors you choose don’t have to exactly match your image — it’s just for accurate pricing.


 

Then I resized the image so that it filled the front of the shirt. I also made sure to select the checkbox that says “keep the white in my image”.

 

Next, get a quote and order a shirt. Mine only cost $24.75 and shipping was free in the U.S. I thought this was a great price and was really happy with the result!

Difficulty Level = 6 [What's this?]

This is a mood lamp I build using 16 LEDs of different colors and small glass vials. The square bottoms of the vials look a lot like glass block, and the glass diffuses and scatters the light in beautiful ways. The software shows random patterns of light and the brightness of each LED can vary — they aren’t simply “on” or “off”.

The Arduino code is pretty complex because it implements PWM (pulse-width modulation) for all 16 LEDs. The Arduino board only has 5 PWM-capable pins, so providing PWM for all 16 pins is accomplished purely in the code. The lamp randomly displays different lighting patterns and can be really mesmerizing. Ok, I know you want to see it in action, so here it is (note that the music is just in the background — the lights are not reacting to it):

Construction

The base of the lamp is a piece of plexiglass about 5 inches square, and all of the wiring is on the underside of the plexi. Each of the 16 LEDs goes into a small socket made from two pins of a female header. I used sockets instead of soldering the LEDs directly so that I could rearrange the colors any way I like.

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