Medical Tricorder Mark I

A handheld tricorder is as good a reason as any to start a project. The science-fiction-derived form factor provides an opportunity to work on a lot of different areas of hardware development like portable power, charging, communications between sensor and microcontroller. And of course you need a user interface so that the values being returned will have some meaning for the user.

[Marcus B] has done a great job with all of this in his first version of a medical tricorder. The current design hosts two sensors, one measures skin temperature using infrared, the other is a pulse sensor.

For us it’s not the number of sensors that makes something a “tricorder” but the ability of the device to use those sensors to make a diagnosis (or to give the user enough hints to come to their own conclusion). [Marcus] shares similar views and with that in mind has designed in a real-time clock and an SD card slot. These can be used to log sensor data over time which may then be able to suggest ailments based on a known set of common diagnosis parameters.

Looking at the image above you may be wondering which chip is the microcontroller. This build is actually a shield for an Arduino hiding underneath.

There’s a demonstration video after the break. And if you find this impressive you won’t want to miss the Open Source Science Tricorder which is one of the finalists for the 2014 Hackaday Prize.

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End Table Kegerator Hides the Tap when You’re Not Looking

What’s better than an ordinary end table? How about an end table that can serve you beer? [Sam] had this exact idea and used his skills to make it a reality. The first step of the build was to acquire an end table that was big enough to hold all of the components for a functional kegerator. This proved to be a bit tricky, but [Sam] got lucky and scored a proper end table from a garage sale for only $5.00.

Next, [Sam] used bathroom sealant to seal up all of the cracks in the end table. This step is important to keep the inside cold. Good insulation will keep the beer colder, while using less electricity. Next, a hole was cut into the top of the table for the draft tower.

The draft tower is mounted to a couple of drawer slides. This allows the tower to raise up and down, keeping it out of sight when you don’t want it. The tower raises and lowers using a simple pulley system. A thin, high strength rope is attached to the tower. The other end is attached to a spool and a small motor. The motor can wind or unwind the spool in order to raise and lower the tower.

The table houses an Arduino, which controls the motor via a homemade H bridge. The Arduino is hooked up to a temperature sensor and a small LCD screen. This way, the users can see how cold their beer will be before they drink it.

To actually keep the beer cold, [Sam] ripped apart a mini fridge. He moved the compressor and condenser coils to the new table. He had to bend the coils to fit, taking care not to kink them. Finally he threw in the small keg, co2 tank and regulator. The final product is a livingroom gem that provides beer on demand.

Demo video (which is going the wrong way) can be found after the break.

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PID Controlled Glue Gun

Internals of a glue gun controlled with a PID controller

Hot glue falls into the same category of duct tape and zip ties as a versatile material for fixing anything that needs to be stuck together. [Ed]‘s Bosch glue gun served him well, but after a couple of years the temperature regulation stopped working. Rather than buying a new one, he decided to rip it apart.

With the old temperature regulation circuit cooked, [Ed] looked around for something better on eBay. He came across a cheap PID temperature controller, and the Frankengluegun was born.

A thermocouple, affixed with some kapton tape and thermal paste, was used to measure the temperature of the barrel. Power for the glue gun was routed through the PID controller, which uses PWM to accurately controller the temperature. All the wiring could even be routed through the original cord grips for a clean build.

Quality glue guns with accurate temperature control are quite pricey. This solution can be added on to a glue gun for less than $30, and the final product looks just as good.

The Smart Humidor

humidor

If you’re a cigar aficionado, you know storing cigars at the proper temperature and humidity is something you just need to do. Centuries of design have gone into the simple humidor, and now, I guess, it’s time to put some electronics alongside your cigars.

The design of [dzzie]‘s smart humidor consists of an Arduino, WiFi shield, LCD + button shield, and most importantly, a DHT22 temperature and humidity sensor. In a bit of thoughtfulness, only the DHT22 is mounted inside the humidor; everything else is in an enclosure mounted outside the humidor, including a few buttons for clearing alerts and logging when water is added.

The smart humidor reads the DHT22 sensor every 20 minutes and uploads the data to a web server where useful graphs are rendered. The control box will send out an alert email to [dzzie] if the temperature or humidity is out of the desired range.

ATMega & ATtiny Core Temperature Sensors

temp

We don’t know if this will come as a surprise to the regular Hackaday reader, but a whole bunch of Atmel microcontrollers have a very cool feature hidden away in their datasheets. Most of them – everything from the ATMega 168, 328, 32u4, to the ATtiny85 and  84 have a temperature sensor right on the chip. [Connor] did a little bit of research on this sensor and came up with a little bit of code that spits out the core temperature of these Atmel chips over the serial port.

The temperature sensor on these Atmel chips is accessed by writing a code – ’100111′ for the Mega32u4 and ’100010′ for the tiny84, for example – into the ADMUX register on the chip. According to the datasheet, the returned temperature is accurate to +- 10°C, but that can be easily calibrated by holding an ice cube (in a plastic bag, of course) up to the chip.

With a little more code, [Connor] is able to output the temperature of the microcontroller core over a serial port. In testing, his chip started out at 20°C and reached equilibrium at 24°C after about a minute. Pretty neat, and could be used as a temperature sensor for a project in a pinch.

Hack Your Stove in the Name of Homebrewing

stovehack

[Tim] is a homebrewer. Temperature profiling during the mashing process is apparently even more critical than the temperature curve of a solder reflow oven. His stove just wasn’t giving him the level of control he needed, so [Tim] added a PID temperature controller to his stove. Electric stoves generally use an “infinite switch” to control their burners. Infinite switches are little more than a resistor and a bimetallic strip in a single package. Not very good for accurate temperature control. The tricky part of this hack was to make it reversible and to have little visual impact on the stove. A stove top with wires hanging out would not only be dangerous electrically, it would also create a hazardous situation between [Tim] and his wife.

[Tim's] brewpot only fit on the stove’s largest burner, so that was the only one that needed PID control. To keep things simple, he kept the commercial PID controller outside the stove’s enclosure. Inside the stove, [Tim] added a solid state relay. The relay is mounted to a metal plate, which screws to the back of the stove. The relay control lines run to an audio jack on the left side of the stove. Everything can be bypassed with a switch hidden on the right side of the stove. In normal operation, the switch is in “bypass” mode, and the stove works as it always has. When mashing time comes along, [Tim] flips the switch and plugs the jack into his PID controller. The temperature sensor goes into the brewpot itself, so no stove modification was needed there.

The end result is a very clean install that both [Tim] and his wife can enjoy.  Save a few bottles for us, [Tim]!

Temp-Sensitive Automatic Blinds

blindMinder

Any opportunity to shave a few bucks off your power bill is probably worth considering, especially if it’s a device like [Steve Hoefer's] Mini Blind Minder. This little guy staves off (or welcomes) the sun by monitoring the room with a temperature sensor and checking against a setpoint. If the room is too warm or too cool, the top-mounted servo will spin the wand and close or open the blinds, respectively.

[Steve] started by building a homemade Arduino shield from some perfboard to which he added a handful of discrete components: some current-limiting resistors for the RGB LED indicator light and a 10k trim pot for fine-tuning the temp sensor. Although this build forgoes an LCD readout to display precise information, it does provide feedback by stepping the RGB LED’s color through a spectrum of blue to red to indicate how the current room temperature compares to your setpoint. The two momentary pushbuttons beneath the light allow the user to adjust the setpoint up or down.

See the video below for a detailed guide to building your own, and take a look at a similar automatic blinds build from earlier this year that opens and closes in response to ambient light.

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