In this review we examine an interesting, fun and possibly a prankster’s delight – the “Defusable Clock Kit” fromnootropic design. The purpose of this kit is to construct a clock that counts down in a similar method to “movie-style” bombs, and it has terminals to connect four wires to the board. When the countdown timer is beeping away, you need to choose which wire to cut otherwise the “bomb” (alarm) goes off.
Furthermore, it also functions as a normal clock with an alarm, so you can use it daily normal activities. And finally it is based on the Arduino system which allows the kit to be reprogrammed at a later date. Now let’s move forward by examining kit construction.
The kit arrives in a re-sealable antistatic pouch that can be reused without any effort:
Detailed instructions can be found on the product website. The kit has a very clear and well-detailed silk screen on the PCB:
All the parts required are included, as well as an IC socket for the microcontroller:
However it looks like someone in the kitting department was in a hurry, things like this are pretty inexcusable – but recoverable:
Nothing that can’t be fixed carefully with some needle-nose pliers, nevertheless it was somewhat inconvenient. Some beginners may not have the patience or finesse to fix this themselves, and end up with a useless microcontroller. Moving forward, the first parts to solder in are the resistors:
… then to the other lower-profile components:
… and the rest:
Which leaves us with the final product:
The clock is designed around simple Arduino-compatible circuitry, so if you wish to alter the firware for the clock or upload your own sketch, you will need to fit the six-way header pins (in order to connect a USB-FTDI cable). As the pins are horizontal and tend to fall over, it’s easier to solder the first pin from the top of the PCB to hold it in place:
… then turn the PCB over and solder the rest.
Power is supplied via the DC socket on the PCB, and converted to 5V with a typical 7805 regulator. Therefore your input voltage can range between normal levels of 9~12VDC. Once the power is connected you can set the time for the clock and alarm for normal use. However if you feel like some sweat-inducing excitement, connect four wires each between the terminal blocks at the top of the PCB. Then press the red button to start the ten-second countdown. You can also increase or decrease the countdown time.
Your chances of defusing it in time can be quite low – by cutting one wire you can defuse it, by cutting two other wires nothing will happen and the clock keeps ticking – and by cutting the final wire… well, it’s all over. The wires are randomly chosen each time so you can’t predict which will be the correct wire. (Unless you change the firmware). Now let’s see the clock in action:
At this juncture it would be appropriate to warn the users of this kit not to … well, misuse the clock. To be honest I’m surprised such a kit originated from the US in the first place, but then again it never hurts to have a sense of humour. But seriously, to the untrained eye or casual security guard – this kit will look pretty damn real. So no making any mock explosive models with Play-Doh or metal cylinders and leaving them on the train or bus or under someone’s toilet seat. Then again, that would be good for a laugh – so please keep it at home, not in the railway station.
As mentioned earlier this kit is Arduino (Duemilanove) compatible, you can upload new sketches using a 5V FTDI cable or swapping the microcontroller over in another Arduino-style board. You have four LEDs, a 4-digit 7-segment LED module, a buzzer, and four digital I/O pins via the terminal block on the top-right of the PCB which could control external devices. Furthermore you can download and examine the clock sketch to modify or deconstruct it to determine the operation.
Apart from the laughs and possible mayhem you could cause with this, the kit is easy to assemble and works as described. It would make a great present to get someone interested in electronics, or help them with soldering practice. Furthermore it is certainly unique, and would be fun at parties and other events.
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