DIY Electrical Body Fat Analyzer

Whether you are trying to drop some fat or build some muscle, it’s important to track progress. It’s easy enough to track your weight, but weight doesn’t tell the whole story. You might be burning fat but also building muscle, which can make it appear as though you aren’t losing weight at all. A more useful number is body fat percentage. Students from Cornell have developed their own version of an electrical body fat analyzer to help track body fat percentage.

Fat free body mass contains mostly water, whereas fat contains very little water. This means that if you were to pass an electrical current through a body, the overall bioelectrical impedance will vary depending on how much fat or water there is. This isn’t a perfect system, but it can give a rough approximation in a relatively easy way.

The students’ system places an electrode on one hand and another on the opposite foot. This provides the longest electrical path possible in the human body to allow for the most accurate measurement possible. An ATMega1284P is used to generate a 50kHz square wave signal. This signal is opto-isolated for user safety. Another stage of the circuit then uses this source signal to generate a 10ua current source at 50kHz. This is passed through a human body and fed back to the microcontroller for analysis.

The voltage reading is sent to a MATLAB script via serial. The user must also enter in their weight and age. The MATLAB script uses these numbers combined with the voltage reading to estimate the body fat percentage. In order to calibrate the system, the students measured the body fat of 12 of their peers using body fat calipers. They admit that their sample size is too small. All of the sample subjects are about 21 years old and have a similar body fat percentage. This means that their system is currently very accurate for people in this range, but likely less accurate for anyone else. Continue reading “DIY Electrical Body Fat Analyzer”

Make Your Treadmill More Entertaining for $0

Treadmill Computer

Treadmills can often be found on the side of the road, after someone gave up on their running regimen and found that the machine was taking up too much space in their basement. This is great for hackers, since they have some useful parts in them.

However, if you’d like to actually use a treadmill for running, some entertainment would certainly help. [KingJackOff] decided to roll his own treadmill entertainment system out of things he had lying around, bringing the total cost to $0.

He took an old laptop and mounted it in a piece of rigid foam using a gratuitous amount of duct tape. With the screen and keyboard mounted, he added speakers and a slot for the DVD drive. Then a printed graphic was taped to the front, with a nice motivational message.

Lots of people have old laptops lying around with mechanical issues. Broken hinges and frames make them unusable, even though the electronics are fine. Some foam and paper could be all you need to bring one back to life.

[via Reddit]