@@ -106,7 +106,31 @@ After verifying the FSR characteristics, it was time to move the testing into th
After pressing the heel multiple times, and attempting to recreate a walking motion, we were able to get good responses on the oscilloscope, indicating that the FSR exhibits the same functionality when placed within a shoe. In particular, we were able to see exactly when the foot both touched and left the ground in a walking motion, as the oscilloscope registered a gradual increase in pressure when my shoe hit the ground, followed by a corresponding decrease as my foot left the ground. This was particularly important, as we can map the change in pressure in a normal walking stride.
# 4/6/2022 - Shoe insole construction
Now that the FSRs work as intended, it was time to begin work on building the shoe insole. I labeled the FSRs # 1-6, which were placed in the exact same layout as outlined in our design docs. We soldered wires of different colors (each color corresponds to the sensor) to each terminal of the sensor, and heat-shrank the interface between the FSR and the wire connection to incease durability. Afterwards,
Now that the FSRs work as intended, it was time to begin work on building the shoe insole. I labeled the FSRs # 1-6, which were placed in the exact same layout as outlined in our design docs. We soldered wires of different colors (each color corresponds to the sensor) to each terminal of the sensor, and heat-shrank the interface between the FSR and the wire connection to incease durability. Afterwards, I attached the FSRs to the shoe insole using black duck tape, and placed the sensing plane upwards facing the shoe insole. This was done row-by-row, as to ensure that no wires were overlapping any of the FSRs - which could cause multiple FSRs to respond when pressure is only applied to one of the sensors. The wires were carefully cable-managed to come out of the right side of the right shoe, so they can be attached to the ribbon cables connecting to the PCB enclosure (still needs to be done). The wires were trimmed to ensure that all wires were of the same length when emerging out of the shoe insole.
When testing the wearability of the shoe, the wires, which were routed underneath the shoe, could not be felt. This was particularly important, as we want to ensure that the comfort of wearing the IntelliSOLE is not compromised.
# 4/9/2022 - Testing the shoe insole, sending PCB enclosure CAD for printing
The FSRs attached onto the shoe insole were tested to ensure that connections were secure, and that the behavior of the FSRs remain unchanged. Using the breadboard circuit, each FSR was individually tested by connecting jumper cables from the FSR ports on the breadboard to the connections on the shoe insole, and probing the voltage output using an oscilloscope. All FSRs exhibited the same response except for Sensor 5, which seemed to exhibit floating ground characteristics and not respond when pressure is applied.
Upon closer inspection, a tear in the printed wiring within the FSR was found. As this wiring was flat and laminated in a plastic covering, soldering was not possible to fix the broken connection. As such, only five pressure sensors were operational. This could be attributed to the differences in tensile strength between the soldered wires (round, thick and durable) and the printed wires within the FSR assembly.
After testing, I had visited the IIllinois Makerspace Lab to upload our CAD drawings for 3D printing, which was estimated to be complete by the end of next week.
# 4/14/2022 - Durability Testing
The shoe insole was continuously worn and tested for roughly two hours. During walking, I had wanted to observe how comfortable it was to wear the shoe during normal use. While walking, I had noticed that while I did not feel any wires or FSRs housed underneath the insole, the sole felt higher than the other shoe pair with nothing underneath the insoles. When removing the insole upon further inspection, I had found that the wires from Sensor 2 and Sensor 5 had overlapped onto each other. To seperate them and ensure that no wires overlap on each other, I rerouted Sensor 2's wire to follow closer to the edge of the insole. This was easier to do as Sensor 4 was no longer operational, and so it would make no difference if I had run wires over the sensing plane.
After completing the fix, I went for brief runs and found no issues in comfort. When jumping up and down, I had felt some of the wires sticking out of the shoe insole scratching my lower ankle. This was not an issue, as those exposed ends will be connected to the ribbon cables, which were lower in profile.
When completing these tests, I had restested the FSRs to see if the sensor response had changed, which it did not for all sensors. Same degree of linearity was observed as well.
# 4/20/2022 - Testing of Bluetooth Subsystem
The FSRs were connected to the breadboard circuit via alligator cables to test out the functionality of the Bluetooth subsystem. After connecting the power supply and oscilloscope to the breadboard, the analog outputs seen on the oscilloscope were to be corresponded to the response seen on the Bluetooth subsystem. While the oscilloscope read good outputs based on my stepping and walking motions, the user interface did not register all instances of pressure being applied. This could be attributed to the sampling rate of the Signal processing subsystem, where the sampling resolution was not set high enough. After a few software fixes, responses were able to be seen on the User Interface which corresponded to the oscilloscope reponse.
# 4/21/2022 - Mock Demo
We demoed the current state of our project with Hanyin and Prof. Song. As our PCB case hadn't arrived yet, we had to conduct our testing on the breadboard circuit as there was no way of holding the PCB next to the shoe. One of the FSRs were tested, and was connected to the breadboard circuit via jumper cables.
# 4/22 - 4/24/2022 - Arrival of PCB case, Final Product Integration
We've picked up the PCB case on Friday, and work began right away on integrating the shoe insole to the PCB. All ten wires (2 for each sensor) were attached to the exposed wires on the shoe insole, and routed into the PCB enclosure entrance. These cables were then connected to the FSR ports onto the PCB for testing.
When testing the FSR voltage response on the PCB, we had noticed that one of the op-amps rapidly got hot in temperature. When reviewing the PCB design, it was found that the PCB was soldered on backwards, and that the ground line was receiving power. After desoldering re-attaching the op-amp, we'd noticed that we were getting constant high outputs (2.1 V) for some of the FSRs, while one of the FSRs remained at ground, with no change in applying pressure. Only two out of the five FSRs had the desired voltage response. When checking the components on the PCB, nothing seemed to have shorted or heated up.
After more testing, we had localized the issue to that of the amplifiers. When reviewing the PCB design, it was found that there was a mismatch in footprints of the op-amps in the KiCAD design. Due to time constraints, we had chosen to migrate the Data Acquisition circuitry onto a smaller breadboard, while the PCB was used for signal processing and power distribution.
The amplification circuitry was then compressed onto a much smaller breadboard, and was extensively cable-managed in order to fit into the PCB enclosure. The FSR voltage response was tested using the LiPo battery as the power source, and was found to have identical responses as when using the power supply. This was important because it showed that the Power distribution circuitry was regulating the voltage output of the LiPo cell to 3.3 V.
Once the Data Acquisition and Power Distribution circuits were shown to work, the Signal Processing and Bluetooth subsystems were tested. After much trial and error, the User Interface was able to show similar voltage responses as the oscilloscope - establishing successful analog-to-digital conversion, signal processing, and Bluetooth connectivity.
