From the first time that we tested the sensors we realized that we were going to have a problem with connecting the sensor to wires and run them into the shoe. The sensor has to small tabs at then end of it which needs to be attached to wires for connection. From the beginning of the project we had the idea that once we installed the sensors in the shoe we would solder them to the wires which would guarantee a good connection between the sensor and the Lab View hardware. When we received the users manual with the sensors it said that the sensors cannot be soldered. For the initial testing a member of the group had to place the sensor on the table and hold two wires on top of the tabs. This is obviously a very inconsistent way to connect the sensor and could never be used in the final system. The next thing we tried was a female connector with a round end on the other side (Figure 27).
Figure 27 : Female Connector
This allowed us to place the two tabs on the sensor in the female end and run the wires through the other side. We had to make sure that each individual wire was only touching one of the tabs, even though the wires were running through the same hole. The connector was crimped so that the wires would stay in contact with the tabs. These connectors were not made for this and failed miserable, the connector could not be crimped tight enough and the wires pulled out with the slightest of tugs.
The last connection we tried was using individual connectors for the two solder able tabs. We found these connectors in the electrical engineering department and ordered more off the web (Figure 28).
Figure 28 : Individual Female Connector
These connections allowed us to crimp the wire in one side and place an individual tab in the other end. These connectors lock into place, but the tabs were still to skinny to lack into place. We ended up crimping the other end with the tab in it even though it was not made to be crimped. This trapped the tab in the connector but it destroyed the clamping mechanism that was useless anyway. This style of connection was by far the best that we had come up with and secured the tab without having to hold it or tape it.
Now that we know how to connect the sensors to the wires we had to attach the sensors to the insole. We decided to use electrical tape over the sensors to attach them to the insole. Electrical tape was stronger then the scotch tape and held better on the insole. The first thing we did was tape down all of the sensors. The sensors were attached with the active area against the insole and taped over. Originally tape was only placed over the active area of the sensor, not the tabs that extend from them. We attached all of the sensors and wired them. When we began to turn the insole over and place it into the shoe the wires were bent every which direction and pulled on the sensors. This caused the sensors to be lifted off of the insole and caused some of the connections to be undone. We had to use thick wires in order to get the wires to stay connected with the tabs, but this thicker wires were also stiffer which caused the sensors to be pulled when the wires were bent. After the first try and all of the sensors are disconnected due to the pull of the wire we decided that we needed more tape (Figure 29).
Figure 29 : Sensor Attachment
We decided to tape every part of the sensor down to the sole except for the small connector tabs. Once the wires were connected we even taped the wired to the insole to prevent them bending along the insole. This solved the connection problems that we were having.
Now that the sensors are attached to the insole we had to wire them to the circuit board. As mentioned in the last section the wires were taped along the surface of the insole to prevent lifting due to twisting. The wires then needed a way to get out of the shoe. There were two different options to get the wires out of the shoe. The first was to run the wires along the inside of the shoe and up out of the shoe. The second option was to cut holes in the bottom of the shoe and run the wires out of these holes.
Running the wires out of the top of the shoe means that the shoe would not have to be cut and the integrity of the shoe would not be compromised. The wires would have to run along the back inner wall of the shoe and out the top. This would cause discomfort to the user because the wires are running along their foot and there would be less room in the shoe so the foot would not fit as good. The wires would also have to be bent many times coming out of the shoe, they would be bent at the bottom where the wire comes out from under the insole and bent again once they get out of the shoe to go into the circuit board. This could cause pulling on the sensor connections.
Cutting holes in the shoe was the other option. We would cut slits in the shoe at the bottom, just above the hard foam on the bottom of the shoe. The cloth would cut easier then the foam. If we decided to do this we had to make sure to make the slits small enough so that they do not compromise the strength of the shoe. If the slits are to big the shoe could lose strength and it will bend over easily when the user is running. This would cause an ankle injury to the user, which would obviously be a bad situation. Running the wires out of the bottom of the shoe gives an easier path for the wires. The wires can run straight from the insole out of the shoe and not be bent upwards. This would reduce the pulling on the sensor connection. They would also run straight out of the shoe to the circuit board. The holes would be placed on the outside of the shoe. That way they can run to the circuit board without getting in the way of the user's other foot.
After analyzing the two options we decided to run the wires out of slits at the bottom of the shoes (Figure 30).
Figure 30 : Wires running out from shoe
We only had to make three small slits in the shoe and were able to fit all of the wires through them. This minimized the bending in the wires and kept the wires out of the user's way which maintained the comfort of the shoe.
The shoe is equipped with eight sensors which mean that there are a total of 16 wires running out of the shoe. The wires were color coded depending on the size of the sensor. The large sensor used green wire, the medium sensor used black wire, and the small sensor used red wire. When the sensors were initially wired and run out of the shoe the two wires were taped together and numbered. A picture was drawn numbering which sensor was given what number so that we could keep track of them when they were connected to the bread board. The wires also had to be quite long. We made each of the wires 6 feet long because they had to run from the sensor to the breadboard. The breadboard was placed on the computer which is sitting next the treadmill where the shoe is tested. The length had to be extended to six feet to account for the extension of the wires during the running motion. The wires were first connected to the sensors then the entire length was run through the hole in the shoe individually. The process was time consuming and tedious, the final product was a confusing maze of wires (Figure 31).
Figure 31 : Wires Coming out of Shoe
All of these wires then had to be run to the circuit board. The circuit board also had the output voltage running to the connector block, which was another sixteen wires. This made the circuit board a large grouping of wires (Figure 32).
Figure 32 : Final Circuit Board Wiring
The group had hoped to use a soldered board for the circuit once the system was perfected. This would reduce the confusion on the circuit board and ensure that all of the connections on the circuit board would be good. We ended up running out of time in testing and programming to get a chance of using the soldering board. If the system was ever to be sold it would have to be wireless or at the very least have all of the connections soldered.