Building a replacement for a broken dehumidifier controller

dehumidifier-replacement-controller

We’ve thought of doing a project like this ourselves as the dehumidifier we ordered online runs the fan 24/7 no matter what the humidity conditions. But it wasn’t that [Davide Gironi] was unhappy with the features on his unit. It’s that the dehumidifier controller stopped working so he replaced it with one of his own design. The original humidity sensor was mechanical and simply broke. He used an AVR along with a humidity and frost sensor to get the appliance up and running again.

A DHT22 humidity sensor is polled by the ATmega8 chip and compared to the user-adjustable trimpot value. If it is above that threshold the unit is switched on using one of the relays seen in the image above. The one problem you have to watch out for when using compressor cooled appliances is ice accumulation on the radiator. [Davide] uses a thermistor for temperature feedback, switching the compressor off when it gets below 7C and turning it back on again when it is above 12C.

The replacement still uses the reservoir sensor and indicator LEDs. We, however, would recommend using the watchdog timer on the chip to ensure that it is reset if something goes wrong in the code.

Adding Bluetooth remote control to PC speakers

adding-bluetooth-remote-control-to-pc-speakers

[Andrzej's] plain old computer speakers are ordinary no more. He pulled off a fairly complicated hack which now lets him control speakers via Bluetooth.

He had a set of Creative brand computer speakers with a volume potentiometer that needed replacing. He was having trouble finding a drop-in replacement part and decided he would just go with a rotary encoder. Obviously you can’t just drop one of those in, he would need a microcontroller to monitor the encoder and translate the change into the appropriate resistance. He figured if he was going this far he might as well make the most out of the uC.

Above you can see all the stuff he crammed into the original case. The rotary encoder is seen on the lower left. An ATmega8 is on a PCB he made himself. The white part to the left is a digital potentiometer which feeds the resistance to the original speaker PCB. On the left is the Bluetooth module which lets him control everything from his phone. You can see a demo of that after the break.

[Read more...]

Atomic skull clock reminds us we’re dying

atomic-skull-clock

Whether you like it or not, every second that passes brings you one step closer to your own demise. It’s not a comforting topic to dwell upon, but it’s reality. This art installation entitled ‘Memento Mori’ is a haunting reminder of just that. Even with all the advanced technology we have today, we still have absolutely no way of knowing just when our time will come.

[Martin] cast a real human skull, then added a 4 digit LED display that’s attached to a rubidium atomic clock (running a FE-5680A frequency standard). The display counts down a single second over and over, measured in millisecond-steps, from 1.000 to 0.001. He built a custom electronic circuit to convert the 10 MHz sine wave into a 1 kHz pulse signal, and used ATmega8 chips running an Arduino sketch to do the rest of the dirty work.

Watching the video after the break, with that smooth mysterious music in the background, one can’t help but ponder our mortality. On a personal note, this totally feels like something you’d find in a video game.

[Thanks Martin]

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Hacking a Coffee Machine for a Better Brew

Coffee Machine

Senseo coffee makers are automated brewers that use coffee pods. [Ronald] had one, but wasn’t satisfied with the quality of the coffee it produced. His solution was to hack it apart and build his own automatic coffee machine with the innards.

The coffee brewing part of the system is controlled by an ATmega8. This reads the temperature using the NTC sensor from the original machine and actuates the various parts of the Senseo machine, and the added grinder. The timing was all done by trial and error, optimizing for the best cup of coffee.

Keeping with the trend of adding Raspberry Pis to everything, [Ronald] connected one to this build for remote control. He runs a very hacked version of LCD2USB which deals with communicating with the RPi. An Apache web server hosts a PHP script to provide a user interface, which runs a C program to tell the system to start brewing.

Unfortunately, [Ronald] didn’t give us a link to his web interface, so we can’t remotely brew him coffee. However he did provide all of the source for the project in his write up.

Nixie clock that doesn’t skimp on the number of tubes

[Nina Blum] figures that if you’re going to the trouble of driving Nixie tubes you might as well use a lot of them. The details about this clock, which were sent directly to our tips line, lists a total of thirteen tubes used. There are six Russian IN-8 tubes (large digits), four Z573M tubes (small digits), but the colon tubes and the sine wave tube part numbers were not specified.

An ATmega8 controls the segments via a set of transistors. To operate the display [Nina] included a user interface made from five buttons and a four line character LCD. There is a video showing off the menu system that includes a way to set the time, date, and toggle the various illuminated bits. We’re waiting for permission to post that clip on our YouTube channel as [Nina] only included a Rapidshare link to the movie. Right now you’ll find more images after the break and we’ll embed the video if we get to okay.

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Nixie Clock Without a PCB

Looking for an artistic way to build circuits? Don’t want to design a PCB? The Lethal Nixie Tube Clock is a free form circuit that gives you the time one digit at a time. It uses a IN-1 Nixie tube to display the digits. This is driven by ten MPSA42 high voltage transistors. A IRF520 N-FET, inductor, and a diode are used as a switching power supply that generates the high voltage needed to drive the Nixie tube. It’s probably not lethal, but there are exposed high voltages in the cube. You’d definitely regret touching it.

An ATMega8 is used to control the clock. It drives the various digits of the Nixie tube, and generates a PWM output to switch the high voltage supply. Unfortunately, the schematic has been lost. If you’re interested in the switching supply, it’s likely similar to the one explained here.

Check out a video of the clock after the break.

Via Dangerous Prototypes

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Controlling your webcam with an old Guitar Hero pedal

Hackaday reader [Tom Price] often uses Skype to communicate with family near and far, but he was getting tired of adjusting his webcam each time his kids moved out of frame. While the solution he came up with isn’t fully automated, it is hands-free, which is good enough for his purposes.

[Tom] was looking around for an electronic foot pedal of some sort when he came across a wireless 3rd party Guitar Hero peripheral that happened to fit the bill. Using an Arduino library created by [Bill Porter], he was quickly able to get the toy to communicate with an Arduino-flashed Atmega8, but things kind of fell flat when it came time to relay signals back to his computer. Using another Atmega8 along with the PS2X library, he was able to emulate the Guitar Hero controller that his foot pedal was looking for.

With the pedal portion of his project wrapped up, he focused on his webcam. [Tom] mounted the camera on a small servo, which he then wired up to the receiving end of his foot pedal rig. As you can see in the video below, he can now pan his camera across the room with a tap of his foot, rather than leaning in and manually adjusting it.

[Read more...]

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