Arduino FIO DS18B20 Temperature Logger

We have a Arduino Fio temperature logger, so now maybe we can increase the accuracy by adding an external temperature sensor. I have a couple of DS18B20 Programmable Resolution 1-Wire Digital Thermometers, so I thought, heck, let’s try one out!

These temperature sensors are much more accurate out-of-the-box, so I don’t need to deal with calibration (which I did need to worry about with the internal thermometer). In addition, using separate, discrete components allows for the possibility of putting temperature sensors directly on/in whatever you may want to measure (rather than merely measuring the ambient temperature) and the potential for multiple temperature sensors with a single Arduino Fio (which are available at

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Arduino FIO Internal Voltmeter and Thermometer

Let’s extend the low power Ardunio Fio + Xbee setup that I previously blogged about.  I wanted to see if I could create a simple wireless temperature sensor that could allow for long(er) term logging.  Interestingly, the ATmega328P on the Arduino Fio has both a “secret” internal thermometer and internal voltmeter, meaning that I could (potentially) create a wireless sensor with no external additional external components (other than the Fio, XBee, and battery).

So, taking advantage of the available hardware and the code available, I went about creating a wireless temperature logger using an Arduino Fio (available from and two XBees (one for the Fio and one for the coordinator).

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Arduino FIO Low Power Setup

As usually, I have been very sporadic in posting new/updated projects due to my prioritization of my doctoral work (i.e., not much time for fun little electronics projects!).  However, I’ve been playing around with the Arduino Fio (available from in my free time for a little while now, so I wanted to post some notes on a very low power usage setup that I was able to put together.

As my free hobby time has dwindled, so has the time I’ve been able to devote to debugging programs written for my little Microchip PICs.  So, given my limited time, I decided to dive right into Arduinos — which utilize a higher-level programming language, making things a little quicker and easier for me to tinker — and try to get some wireless communication working.  After looking through the possibilities, I settled on the Arduino Fio.  The Arduino Fio is a great little Arduino-compatible board that includes a socket for an XBee 802.15.4 wireless module along with a LiPo plug and charger circuit.

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Calculating the COM of a Spherical Plot

What is everyone excited for??? More math! Ok, maybe not, but I’ll come back to the electronics projects later (including investigating the Parallax RFID reader, Arduino FIO, and heck, maybe even some more LED fun). In the meantime, let’s get back to math.

What do the volume calculations look like, and how would one go about calculating the center of mass/geometric centroid of a spherical plot? More after the break…
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Calculating the COM of a 3D Surface of Revolution

My current research at Rutgers focuses on identifying the cognitive mechanisms that are employed when perceiving the shape and structure of 3D objects. One of the little problems that I had to overcome was finding out how to calculate the center of mass/gravity of a 3D surface of revolution analytically. Specifically, I needed to calculate the COM for conical frustums with and without an attached part (which was also analytically generated).

Unfortunately, it wasn’t as easy to derive as I assumed, but the steps toward that end are pretty straightforward.  After the break you can see the general equation I ultimately derived for calculating the COM in 3D-space.
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