How Many Punches Does It Take?

Do you ever wonder just how many punches you have thrown? The answer is going to be different if you happen to use a punching bag as part of your exercise routine. So is the case with the [DuctTapeMechanic] and while restoring an old speed ball punching bag, he decided to combine his passions for sports and electronics by adding a punch counter.

Perhaps most interesting in this build is the method used to monitor the bag. A capacitance proximity sensor most often used for industrial automation is mounted in the wooden base. He just calls it “an NPN capacitive sensor” without mentioning part number but these are rather easy to find from the usual places. It has no problem sensing each punch — assuming you swing strong enough so that the bag comes near the sensor. Two battery packs, an Arduino, and an optocoupler round out the bill of materials. We were a little disappointed not to see any duct tape in the construction of this project, but since the electronics are outside and exposed to the elements, maybe duct tape will be used to install a roof in a future episode.

The [DuctTapeMechanic] likes to repurpose items which would otherwise be thrown away, which is something to be applauded. The frame of this punching bag was welded from a discarded metal bed frame (a regular occupant of crawl spaces and self storage places), and you might remember he repurposed the electric motor from a discarded clothes dryer last month, changing it into a disk sander.

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Capacitance Sensor Guide (AD7746)

capacitive_sensor

[Marcus] has written up his experiences using the AD7746 capacitance sensor. He used the SparkFun breakout board in conjunction with an Arduino. The available Arduino code wasn’t that great so he rewrote it to be easier to understand. The AD7746 is an I2C device that can be continuously read, but this doesn’t mesh well with the Wiring libraries. Additionally, the calibration routine from the data sheet is difficult to understand. He’s included all of the code he used plus a Processing sketch to help visualize the input which will hopefully make your experience with the chip much more smooth.