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Stephen’s Status Report for 2/26

The beginning of this week was primarily spent preparing for the design presentation, as we needed to finalize our slides as a group and I personally needed to practice for the presentation itself.

However, I also began testing my various piezoelectric sensors this week so I could narrow down and hopefully select a final component that will go into the final design. Initially, I had three piezoelectric options.

  1. The Flexiforce Piezoelectric Sensor we purchased from SparkFun (Bottom)
  2. Two FSR 400 Series sensors from Interlink Electronics (referred to as IE going forward) that I had left over from a previous project (Middle)
  3. Some cheap handmade Piezoelectric sensors I purchased off Amazon (Top)

After just some quick initial force tests, it was clear that the FlexiForce sensor was the least easy sensor to use. When tapping the sensor with a level of force similar to that of a hit with a drum stick, the resistance hardly changed, and even when applying as much force as I could with my fingers, the change was still only half that of the other two sensors. On the other hand, both the IE FSR and discount Amazon sensors worked much better, with quick and large responses to only light applications of force. However, the Amazon sensors performed poorly in the test I performed before turning on the camera, which gives me the concern they may act inconsistently if used in the final product. As such, I’ve decided to focus all my testing on the IE FSR going forward, as that one seems to be the most promising sensor.

First clip: FlexiForce

Second Clip: Amazon sensors

Third Clip: IE FSR

After selecting my final sensor, I began familiarizing myself with Fusion 360, so that I can 3D print an initial draft of the drum pad housing. Once I have this complete, I’ll be able to combine it with the IE FSR and the Neoprene rubber sheets to create a prototype drum pad, which should greatly aid in future testing by better replicating the expected endcase environment. Here is the module I’ve developed so far using Fusion 360.

The sensor will be fixed to the raised central platform and all the needed supporting circuitry will be located in the cavity underneath it. Additionally, the gap in the base on one side of the module will be used for connecting this module to another module that will house the ESP32 development board. Lastly, we should be able to attach a 3D printed sheet to the bottom of this module after placing the circuitry inside, which should protect the sensitive circuitry inside.

After designing this module, I began working with the ESP32 development board, as this one is slightly different than the ones I’ve used in the past and as such I expected that I’d have some issues getting it to work as my last board did. As I expected, I have been encountering some difficulties but I expect to be able to run simple code by the end of this weekend.

My plans going forward for the rest of the week are to work more with the ESP32 so that going into spring break I’ll be ready to jump right into coding the ESP32’s ADC features. Once I have the ADC features implemented and I have connected it with my sensors I’ll then begin working on sending the ADC information over USB in a form recognizable by George’s program, which should set me up well for reaching MVP by our goal date next month.

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Stephen’s Status Report for 2/19

Last week, I submitted purchase requests for the items in my initial testing BOM so that they could be ordered on Tuesday 2/15 and hopefully arrive on 2/17.  During the stretch from 2/13 – 2/17, I worked on developing a testing plan such that when the components arrived I would already know what tests I needed to perform to assess the quality of these initial parts.

These initial tests can be found here: test_plans_01

I retrieved the components in the afternoon of 2/17 and everything matched my expectations other than the Neoprene rubber sheets. Specifically, the Neoprene seems less rigid than I anticipated, which isn’t a catastrophic or even a particularly large issue, but this does mean that the drum pads should be made thinner than originally planned to avoid too much loss of force as the pads compress. To compensate, I now plan on placing a rigid material (such as plastic) under the neoprene to create extra drum thickness without losing much more force.

On 2/18, I spent most of the day editing the design presentation slides that pertained to the hardware sections of the presentation so that we could receive feedback over the weekend. Unfortunately, this took longer than expected and so I didn’t have time to perform the tests yesterday (2/18). My current plan is to perform these tests later today (2/19), and if I finish early I may be able to edit this report before midnight.

For the next week, I’d like to finish all outstanding tests I have planned, develop and perform any new tests I deem necessary based on the results of those tests, and begin designing a 3D model of the drum pad prototype using Fusion 360.

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Stephen’s Status Report for 2/12

The weekend of 2/5 and 2/6 was primarily spent revising the proposal presentation based on feedback we had received during the week before that. Afterwards from 2/7 through 2/12,  I researched component options and drafted a Bill of Materials (BOM) for our first round of purchases.

(Sorry the image is blurry. I’ve attached the Excel sheet at the end of this post for better clarity)

The five items in this BOM are a piezoresistive force sensor, op-amps (for use with the sensor), a set of cheaper piezoresistive sensors (as a back-up precaution in case the higher quality sensor is damaged), neoprene rubber sheets, and an ESP32 development board. Altogether, these components will form the initial drum pad prototype we’ll need to assess the difficulty of converting forces into electrical signals. If everything goes well with these initial tests, it will even become possible to begin programming the ESP32 to receive these signals and communicate them to a PC, which would allow us to test the software side of this project more easily.

One important detail to note here is the fact that the rubber sheets are made of neoprene. From my research, neoprene is a quality elastic substance which should produce the bounce we’ll need for our drum pads, unlike other synthetic rubbers like polynorbornene. I would’ve liked to order some natural rubber as well to compare the two options, but natural rubber is far more expensive than neoprene and we wouldn’t be able to afford natural rubber for all our drum pads while remaining in our $600 budget.

Regarding ordering/shipping dates, this research unfortunately took longer than expected and so I wasn’t able to submit this order by Thursday (2/10) and as such it will go out this next Tuesday instead (2/15). This is suboptimal scheduling-wise, so to mitigate this loss of time I opted for the quicker shipping options of each product not available through Amazon and I currently plan on developing my testing plans for these components before their arrival so that I’ll be ready to jump directly into testing once they arrive (expected arrival is 2/17). By the next update (2/19) I hope to have these components within my possession and have collected data on the force sensitivity of the sensor.

Here is the BOM in excel form: BOM_18500