I'm involved in a Taekwondo school that works with our local Parks and Recreation Department to teach martial arts to young people and families. We have use of the city's facilities, and the city helps to promote the class so that everyone can learn taekwondo if they want to. One of the classes that we teach is for younger students, and it is called Wee Warriors.
It's always a challenge to keep younger students focused on their training, so I decided to build an interactive punching and kicking dummy that would hold their interest, and Frank N. Stein was born!
Step 1: Pour the Base and Add Wheels
I started out by putting a piece of plywood inside the tub, across one lower edge. I added vinyl wheels to this piece of wood, so that when the concrete dried, I would have recessed wheels to allow me to move the (heavy!) dummy across the gym floor without scratching it. While the concrete was still wet, I also added a 4 x 4 post with metal "L" brackets screwed to it. The brackets gave the concrete something to grab on to, so that the post would not simply slide out of the dry concrete.
Step 2: Prepare Piezo Sensors
I had a handful of piezo sensors, so I decided to use four of them for this project. I used epoxy to attach each of the sensors to a six-inch steel ruler that I got at the local surplus yard. I used a piece of cat 5 cable to connect the sensors, using a single twisted pair for each sensor.
Step 3: Install Sensors and More Padding
I placed the "body" sensors over a few wraps of carpet padding, but since I had pretty thick, stiff padding for the head, I decided to simply tape the "head" sensor directly to the 4 x 4 post. After the sensors were in place, I finished wrapping the carpet padding around the body section, and added a stiff portable kicking target to the head area. I added a surplus Army duffle bag to the body area, and a padded food delivery bag to the head. I chose these things because they were just lying around the house.
Step 4: Duct Tape!
Once everything was in place, it was time for a tough outer covering, and that meant duct tape. Two full rolls, wrapped around and around, gave me a tough exterior. After the tape was in place, I hooked the sensors up to the oscilloscope, just to make sure I had a usable signal from the piezo elements. Everything looked great!
Step 5: Install Some Blinky Lights
I found a bunch of "LED Flashing Steps" (blinky lights) on closeout at Radio Shack. These are designed for runners and joggers, and are made to be threaded through the laces of the shoes. They flash brightly on impact, so I added about ten of them to the body of the dummy. I cut small cavities in the shape of the blinky lights, and embedded them so their surface was flush with the surface of the dummy. They are small enough so that, even if punched or kicked, they will sink into the padding and do no damage, but will flash brightly.
Step 6: Build the Control Box and Add the Edison
I wanted a control box that was convenient and tough, yet that could be removed and repaired at any time, so I decided to use a RJ45 ethernet jack to attach the sensors. This made it easy to unplug and remove if necessary. Because the control box is subject to some amount of shock from being mounted to a punching/kicking dummy, the Edison board is suspended from the four corners of the box on springs. I am looking forward to doing a lot more with this system, so I also mounted a self-stick membrane keypad that I got on closeout at a local electronics store for 25 cents. I intend to add routines for various games and routines to keep the kids interested, so now was a good time to add it. Down the road, I'll be wiring the keypad to the Edison, but for now it is simply attached to the box without labels. I did print a sheet showing the location of all 36 available buttons, but they have no labels as of yet.
Step 7: Bluetooth Feedback
The cool thing about the Edison is that it is able to talk to a Bluetooth speaker, cell phone or tablet. Quite honestly, I ran out of time to get past the testing stages for this part, but I was able to have the Edison talk to a small Popdrop Bluetooth speaker I have lying around. The idea is to use a large, amplified Bluetooth speaker. Using Arduino code, we read the signals from the piezo sensors that are plugged into A0, A1, A2 and A3. We've set a minimum level for the Edison to react to a signal, so background noise is ignored. When Frank N. Stein takes a punch or kick, the increased signal is picked up by the Edison, and it sends one of a number of sound files directly to the speaker via Bluetooth. The sound files say things like "OUCH!", "THAT HURTS!", "MY MOMMA CAN HIT HARDER THAN THAT!", as well as several sound clips from famous movies (think Ahh-nold!). The flashing lights on the front of the dummy, combined with the audio feedback, keeps our Wee Warriors coming back to class again and again. I brought Frank back to my lab to do some upgrades, and I was bombarded with "When are you bringing Frank back?" from all of the kids, so I'd call the project a success, even though he's got plenty of improvements scheduled.