Personal Accomplishments
1. Ordered and acquired components (1hr): I ordered an MCP6004-I/P op-amp to construct the recommended circuit as described in the FlexiForce A301-100 datasheet. I also scoured the ECE lab rooms to acquire other components (with TA permission of course) such as 100k potentiometers, resistors, wires, capacitors, oscilloscopes, digital multi-meters, and power supplies.
2. Sensor setup & ADC setup & sensor calibration (further testing required) (7hr): After constructing the recomended circuit in the A301-100 datasheet, to obtain -Vref and Vsupply, where Vref == Vsupply, I used two power supplies, one supplying 0.5V and -0.5V. Then, I hooked on a multi-meter to the Vout of the op-amp and pressed on the sensor with varying force to observe the output change. I did observe a change, however, Vout reached 0.5V with insignificant force. Realizing that I needed to modify the circuit to allow for a larger voltage range and tune the gain accordingly, I requested Alex’s help, for which he computed and provided me with the proper component values necessary to achieve this. After testing, the sensor functioned as predicted, and we we’re able to obtain readings ranging from 0 – 2V, where grams of force correlated with mV of change and extreme force encroached on 2V.
Then, I booted up an STM32 Nucleo board, configured its ADC to use a 12-bit resolution, and measured the Vout pin of the MCP6004 to verify the sensor reading using a multi-meter. Lastly, I performed bend tests on the sensor while reading, for which there were no obvious differences via inspection in measurement. Further testing is required where we will place the sensor on scale and measure weights on it to calibrate. We will perform the same test on a bent sensor to identify changes in sensitivity. Side-note: during this testing, I identified that we will require a Negative LDO (Negative Linear Regulator) to produce -Vref in our final design (as we won’t use power supplies). I will investigate eligible components.
3. Mandatory Lab Meetings (4h): During our lab meetings, we recieved great feedback. We were able to discuss design corners in our project and identify areas of ambiguity. One very useful point made by our advisor was the tuning of our gain for our sensor readings. We applied this feedback in our sensor testing this week, it was very helpful! We also had time to meet with our team to perform schedule reviews and work on the design presentation.
Progress
- My progress is on schedule, my next step is to continue calibrating the sensor and testing it using a scale and weights, along with more bend testing.
Next Week tasks & goals
- Test the A301-100 sensor with weights and tune the ADC and/or voltage range/gain if necessary. Also test the haptic driver, which will be used to alarm users.