Cute Countdown Timer Reminds you of Impending Doom

As things get busy, whether it be an upcoming product launch, a pregnancy, or even the release of your favorite game (or movie!) sometimes it’s nice to have a little countdown timer. Not an app on your phone, but a tangible, physical timer to set on your desk. Which is why SevenSeg is such a cute idea.

[Mohit] wanted to design something that was simple, but aesthetically pleasing — he’d seen free-form electronic projects before and wanted to give it a shot. What he came up with is pretty elegant! A seven segment display is connected via 1/32″ brass rods to the controller, a Particle Photon — which is kind of like a Teensy with WiFi for the internet of things. After putting a few resistors in line with the display, and a bit of frustrating bending of wire later, and SevenSeg was complete.

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Nice Looking Countdown Timer for the Home Game Show Enthusiast

Every couple of weeks, [Roo’s] place of employment, TMW Unlimited, has a contest. This contest takes place in the form of a game show and the contestants have 30 seconds to pitch their current project to the group. A panel of judges vote on the best pitches. Winners receive cupcakes and drinks. Originally, stopwatches were used to keep track of the elapsed time, however, a stopwatch is not very game showy. [Roo] set out to make a countdown timer to add some authenticity to the bi-weekly event.

The main enclosure is a plastic fence post. Fifteen holes and 15 large LEDs are covered up by large plastic translucent spheres. End caps were designed and 3D printed to not only make the rig look good but also to serve as a speaker mount. Inside resides an Arduino that does the counting and turns off the row of lights, one every 2 seconds, as the countdown continues. A speaker not only ticks and tocks its way down with the lights, it also buzzes when time is up. Starting and resetting the timer is as easy as pushing a single button mounted on the case.

If you’ve already built a game show timer, you may want to check out this DIY game buzzer system!

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An Introduction to Clock Dividers and Psychological Warfare

A while ago, [nsayer] was inspired by a Hackaday post to build one of the most insidious means of psychological warfare. I speak, of course, of the [Lord Vetinari] clock, a clock that ticks at random intervals, but still keeps accurate time. His build, the Crazy Clock, is a small controller board for off-the-shelf clock movements that adds the [Vetinari] feature to any clock by soldering only a few wires.

The Crazy Clock is a pretty simple device consisting of only a 32.768 kHz crystal, a microcontroller, and a few transistors to pulse the movement of a clock mechanism. While psyops is great, it recently occurred to [nsayer] that this device could be used for other build.

Since the output of the Crazy Clock doesn’t necessarily have to be connected to a clock movement, [nsayer] decided to connect a LED, generating a 60Hz flashing light for a phonograph strobe. This is easy with timer prescalers and clock dividers; the original 32.768 kHz signal is divided by 8 to produce a clock that ticks every 4.096 kHz.  Divide that again by 120, and you get 34 2/15. Yes, this is all stuff you learned in fourth grade, and if you’re smarter than a third grader you can eventually whittle a 32.768 kHz clock down to a nice, round, binary number – exactly what you need for computing time.

[nsayer] posted a 240 fps (vertical) video of his Crazy Clock blinking at 60 Hz. You can see that below.

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AVR Hardware Timer Tricked Into One-Shot

[Josh] has written up two posts that those of you who use AVRs might find handy. The first post documents a C library that implements a jitter-free one-shot timer. The second post explains how it works. We think it’s such a good idea that we’re going to spoil it for you, but go ahead and read his links and check out his code.

A one-shot is a pulse generator that runs once and only once. You trigger it, it produces the desired pulse, and that’s all she wrote. Why is this handy? Many external ICs that you’ll interface with have minimum durations for signal pulses that must be respected. You could program the AVR to toggle a pin high and then sit around and wait until it’s time to toggle the pin low again, but this wastes valuable CPU time, isn’t going to be very precise, and is susceptible to timing discrepancies if interrupt routines fire in the mean time.

You’d think that you could use the hardware timers for this, but it’s not straightforward. Normally, the timers are free-running; the counter that’s keeping track of time rolls over the top and starts over again. But we just want one pulse.

[Josh]’s very clever idea abuses the timer/counter’s TOP and MATCH values in “Fast PWM” mode. Essentially you trick the counter into never matching by setting TOP below MATCH. This means that the counter spins in its loop between zero and TOP forever, doing nothing.

To break it out of its loop and enable the one-shot, you manually set the counter to a value above TOP and let it go. As it counts up, it’ll eventually hit MATCH, turn on your pin, and then keep counting. When it rolls over the top (255 + 1 = 0 for the 8-bit AVRs), your pin will be correctly turned off again and then the counter re-enters its loop. The one-shot won’t fire until you manually set the counter higher than TOP again.

So there you have it, a one-shot depending only on the hardware timer/counter module and thus immune to jitter and consuming no CPU time at all. Our hats off to you, [Josh]. Clever hack.

A Kitchen Timer Fit for MacGyver

Here’s a project that you don’t want to bring into an airport, ship through the mail, or probably even remove from your home. [ProjectGeek] has built himself a simple kitchen timer masquerading as a bomb. The build is actually pretty simple, but the end result is something that would look at home in a Hollywood action flick.

The timer circuit is built from four simple components. An 8051 microcontroller board is used as the primary controller and timer. The code is available on GitHub. This board is attached to a another board containing four momentary push buttons. These are used to program the timer and to stop the buzzing. Another board containing four 7-segment displays is used to show the remaining time on the timer. A simple piezo buzzer is used to actually alert you when the timer has run out. All of these components are connected with colorful jumper wires.

The physical part of this build is made from easily available components. Old newspapers are rolled up to form the “explosive” sticks. These are then covered in plain brown paper ordinarily used to cover text books. The rolls are bundled together and fixed with electrical tape. The electronics can then be attached to the base with some hot glue or double-sided tape.

DIY Hot Wheels Drag Race Timer

[Apachexmd] wanted to do something fun for his three-year-old son’s birthday party. Knowing how cool race cars are, he opted to build his own Hot Wheels drag race timer. He didn’t take the easy way out either. He put both his electronics and 3D printing skills to the test with this project.

The system has two main components. First, there’s the starting gate. The cars all have to leave the gate at the same time for a fair race, so [Apachexmd] needed a way to make this electronically controlled. His solution was to use a servo connected to a hinge. The hinge has four machine screws, one for each car. When the servo is rotated in one direction, the hinge pushes the screws out through holes in the track. This keeps the cars from moving on the downward slope. When the start button is pressed, the screws are pulled back and the cars are free to let gravity take over.

The second component is the finish line. Underneath the track are four laser diodes. These shine upwards through holes drilled into the track. Four phototransistors are mounted up above. These act as sensors to detect when the laser beam is broken by a car. It works similarly to a laser trip wire alarm system. The sensors are aimed downwards and covered in black tape to block out extra light noise.

Also above the track are eight 7-segment displays; two for each car. The system is able to keep track of the order in which the cars cross the finish line. When the race ends, it displays which place each car came in above the corresponding track. The system also keeps track of the winning car’s time in seconds and displays this on the display as well.

The system runs on an Arduino and is built almost exclusively out of custom designed 3D printed components. Since all of the components are designed to fit perfectly, the end result is a very slick race timer. Maybe next [Apachexmd] can add in a radar gun to clock top speed. Check out the video below to see it in action. Continue reading “DIY Hot Wheels Drag Race Timer”

ATtiny Watering Timer Turns off the Water When You Forget

ATtiny Water Timer

A pal of [Kyle’s] was regularly leaving his sprinkler on for too long. He also had forgotten to turn the water off while topping off his pool a couple of times, an embarrassing and wasteful situation. Being such a good friend, [Kyle] offered to make him a water timer. This isn’t a regular water timer that turns the water on and off at the same time every day. This device allows the user to push a button to have the unit switch on a solenoid valve, permitting water flow. After a predetermined amount of time the unit removes power to the solenoid valve which stops the water flow, successfully preventing pool overflows and excessive watering.

[Kyle] started off his design using a 555 chip to do the counting. He quickly became worried that timer lengths over 10 minutes would cause inconsistent functionality due to the leakage current of the capacitor and the charge current of the resistor. There are ways around this, but rather than complicate the design he switched to an ATtiny microcontroller. The added benefit of the ATtiny is that he could connect up a potentiometer to adjust the on-time without replacing parts or making a new unit. When the potentiometer is turned, the on-board LED will flash a number of times which corresponds with the delay in minutes. Ten flashes means a 10 minute delay. It’s a simple and clear interface.

As if the home etched PCB wasn’t cool enough, [Kyle] 3D printed up a case for the unit. The case permits access to the screw terminals and has provisions for the indicator LEDs. Check out the integrated flap in the top of the case. When this portion of the case is pushed in, it presses the PCB-mounted on/off switch.

If you are interested in making one, all of the files and code are available on [Kyle’s] site.

via [dangerous prototypes]