Raspberry Pi Solar Charger Current Sensor

Raspberry Pi Current SensorAfter constructing a solar panel and battery system to power a Raspberry Pi, I wanted to find a way to monitor how the battery and charger was performing.  There are several ways to accomplish this task, usually involving a voltage sensor, a current sensor, or both.

A voltage-based sensor can be used to monitor the charge of the battery.  Over a typical day, the battery voltage should rise as the solar panel charges the battery, and then discharge at night while the Raspberry Pi consumes power from the battery.  A common technique for monitoring voltage is to use a voltage divider.  If appropriate resistances are chosen for the voltage divider circuit, the drain on the battery from the sensor is negligable.

Another option is to use a current sensor.  A current sensor placed off of one of the battery terminals will measure how much current is flowing into or out of the battery.   Continue reading “Raspberry Pi Solar Charger Current Sensor”

Ice Clock

iceclockWhile browsing one of our favorite electronic supplier’s web sites, we found that Ladyada sells a really interesting looking clock that uses a vacuum florescent display with eight glowing digits.  This clock proved to be an excellent soldering instruction project for a younger Rusty Nail Workshop helper.

The most interesting feature is the display, which is similar to those found on VCRs, old car radios, and microwave ovens.  The vacuum florescent display was invented in 1967 in Japan and hundreds of millions are used annually around the world.  They are different than an LCD in that they use a filament to emit electrons which are diffused by grids.  The electrons strike a phosphor-coated plate and emit light, and can be manufactured to emit light in different colors. Continue reading “Ice Clock”

A Probotix CNC Machine

V90 CNC MachineOne of my interests involves robotics, especially autonomous self-charging robotics. However, I realize most of my skills center around microprocessors, wood construction techniques, electronics, and some limited computer software skills. I knew I was missing the ability to make custom, metal and/or wood components for my various projects. Thus, the need arose for a CNC machine. If only I knew how to use one!

After some online research, I narrowed down my options to a Shapeoko or a Probotix Fireball V90.  The Shapeoko is significantly cheaper and everything is made with open source license rights.  The Fireball V90 uses some proprietary components, costs more, but has a stronger setup and is more capable than the Shapeoko.  After considering my needs, I decided I wanted to be able to carve and cut both wood and metal, focusing on aluminum.  I’ll need to dedicate space on my workbench for either of these two machines, and dust collection will be an issue for either one.  I understand I will need a separate computer if I purchase the Fireball V90, and I may need separate CAD software.   Continue reading “A Probotix CNC Machine”

iPod Touch Energy Display

Energy DisplayA few of the regular readers of this blog will know that I enjoy using a Web Energy Logger to track information about my home. Not only does this device track temperatures, but I also use it to interface with a Continental Control Systems WattNode. The WattNode allows me to track my energy usage on a minute by minute basis.

Of course, once you have all of this data, you need an interesting way to display it. I originally purchased a Samsung Galaxy 7” Tab, but found the Android operating system difficult to work with. I also found the touch screen to be much less responsive than the iPhone I was using on a daily basis. So I ended up returning the Tab, and I purchased a refurbished Apple iPod Touch (4th Generation). The iPod Touch included a retina display, which was clearly a better screen than any other off-the-shelf LCD I could buy elsewhere. Continue reading “iPod Touch Energy Display”

Solar Powered Raspberry Pi

A solar panel, battery, and Raspberry PiWhen I first heard about the Raspberry Pi, a $35 computer that can run Linux, I was mildly impressed. My first problem was that I did not understand Linux, and my second problem was that I couldn’t figure out a need for a computer this inexpensive. Like all of my other projects, it was just a matter of time before I figured out that not only did I need to have this computer, but that I would find the perfect use for such a device.

Since I had missed the original order date for the Pi, I was either doomed to wait 10+ weeks for one to ship, or I would have to purchase one on E-bay. I debated going with a Gumstix computer instead, but finally settled on an unopened Pi being sold on E-bay. A few days later, I had a Pi to play with. Continue reading “Solar Powered Raspberry Pi”

Crock-Pot Yogurt Controller

A yogurt controller.About a year ago, a friend mentioned how she made yogurt in a Crock-Pot slow cooker. It sounded impressive, and a good way to save on the cost of yogurt. We also figured that we could customize our yogurt recipe and eventually make something that would rival the taste of store-bought yogurt.

After researching a number of ways to make yogurt in a slow cooker, it all essentially came down to heating some milk up to about ~180 degrees fahrenheit, then cooling it down and holding it at approximately 110 degrees for six to eight hours. Since I have some experience working with Arduino microcontrollers, I figured this was a natural project to take to the next level. I also had some experience with PID control theory, so I knew I could write some software that would control a slow cooker and hit a desired set point with minimal error. Continue reading “Crock-Pot Yogurt Controller”

Internet Controlled Robotic Arm

Gripper for a robotic arm.

The motivating factor for the construction of this robotic arm originally came from a tour of the Volvo factory in Göteborg, Sweden. It was during this factory tour that I first saw the massive robotic arms used to pick up car parts and weld them on to the car body. With sparks flying, these were some of the most impressive robots I had ever seen, and if you ever have a chance, take the tour!

Fast forward one month, and I was the proud owner of my first robotic arm kit, a Lynxmotion AL-5D, with the heavy-duty wrist rotate mechanism. Oh boy did I have big plans for this arm! Having some previous experience with Arduino boards, I immediately connected an Arduino Uno to the SSC-32 servo controller that came with the arm. With a little bit of web searching, I was able to find instructions and sample code which had me sending basic commands to each servo. It took another couple of weeks, but I had finally gotten the arm to move the way I wanted. Continue reading “Internet Controlled Robotic Arm”

PongSat Results

The balls sent to the edge of space.Our PongSat ping pong ball was successfully flown on JP Aerospace flight “Away 47” on April 9, 2011 (it is the experiment on the far left above). It reached a height of 85,549 feet before the balloon carrying the ping pong balls popped and the experiment fell back to Earth.

The structure holding the PongSat balls as they went to the edge of space!

The weight of the balloon and payload was approximately 12.5 pounds, and it climbed at an average rate of 1,300 feet per minute. The flight duration was 1 hour, 25 minutes. JP Aerospace recorded a minimum temperature of -74.4 degrees Fahrenheit. The payload was recovered 27.25 miles from the launch site, which was near Pyramid Lake, Nevada. Continue reading “PongSat Results”

PongSat Experiment

Our PongSat ball fully assembled.Today, our first PongSat experiment will be launched to the edge of space! JP Aerospace, a group located in California, offers to fly student experiments that fit inside of a ping pong ball to the edge of space, often over 100,000 feet above the surface of the Earth. Did I mention that they do this at no cost to the experimenter? To get started, you only need to send an e-mail to jpowell@jpaerospace.com.

With the help of my two boys, we created a ping pong ball experiment to measure the temperature and humidity over the course of the ascent and descent of the balloon used to carry the balls up to space. Continue reading “PongSat Experiment”

Delicious Homemade Bread

It's bread!Every once in a while, I find something that I haven’t used in a while and it suddenly catches my interest. In this case, it was an automatic bread maker (machine) which had been sitting in a cupboard unused for the past several years.

After taking it out and dusting it off, I ran to the store and found a bread machine box mix, which just required the addition of water to make a fresh homemade loaf of bread. I dumped in the mix, added the water, turned on the machine, and waited for the magic to happen.

About three hours later, the house was filled with the wonderful scent of fresh bread. When the machine finished, I opened the cover and was immediately disappointed. The bread had risen, but then apparently caved in on itself. What I had was, at best, called a bread bowl instead of a nice fluffy loaf of bread. I ended up tasting it, but it was pointless to cut up and eat. Continue reading “Delicious Homemade Bread”