Author: korenet

This week finalized on key housing design and now in process of printing 16 housings, I flipped the fastening joints to the bottom part of the housing for a better fit, and now the finalized sizing is 24mm x 23mm x 20mm (LxWxH) which fits our sizing constraints better. Overall went through 4 iterations of housing design and fittings. Overall process was a bit slower due to access to 3D printer mishaps

Will be well prepared for next week’s demo, just need to attach velcro on the housings. For inductive coiling, we’ll be waiting on a plug in order to connect to a wall outlet. Overall not much testing to be done here, keys do not wobble at all on their own even now so with velcro they should be quite stuck

This week Question:

1. Now that you are entering into the verification and validation phase of your project, provide a comprehensive update on what tests you have you run or are planning to run. In particular, how will you analyze the anticipated measured results to verify your contribution to the project meets the engineering design requirements or the use case requirements?

   Inductive coil testing: We’ve been making tests at the outputs of the transmitter coil to see what wave is outputted and what is the output voltage by using an oscilloscope to measure at the two inductor points. This allows us to know if the period is what we expect, if the peak to peak voltage is not being shorted or other reasons it may be lower than anticipated and if our output is still a sine like wave. This is primarily for debugging currently, but later on this will be useful to measure what our power efficiency is when we also measure how much current there is going through as well.

   With power efficiency, we’ll also be testing the duration of how long it takes to charge and this will also be related to the power transfer. One method is through using a stop watch and timing how long it takes to charge fully one (as of now it seems to be relatively quickly through a USB-C, so we may be able to measure the whole battery journey from start to finish). It’s important to measure the entire battery charge as it is a curved relation and not linearly, as it becomes more full, it becomes slower to charge.

   For 3D housing, that is just using calipers to measure. We can see how large it is and then also take into account in usage of whether it is comfortable to type on. Perhaps as an addition to the case we will include a wrist rest as the package of components is quite tall, however this is also a normal occurence in high end keyboards. Stability wise has not appear to be an issue either, but we will take into account of a wobble factor (perhaps measured by multiple people seeing how much effort it takes to knock a key down?)

   This week Progress

   This week I made another iteration of changes to the 3D housing and testing for the inductive coiling to determine what configuration the circuit is in. 

Inductive coil: Issues this week were unfortunately soldering issues to create a good pin output to the breadboard with the inductive coils. A few of the solder pads were ripped off due to uncareful measures, but that is just technical difficulties. That’s caused some slow down with circuit testing

We were able to measure the output of the oscillator chip directly (XKT-412) which we determined is similar to a 555 Timer due to it’s constant output. This denotes that our issues with inductive charging is with the power amplifier. Because of the larger resistance of the smaller coils, it affects how the power is transferred. We are still looking through some literacy to understand what could be helped with this, I’ve been referencing some of my 18-421 notes about common source amplifiers to see what the specific remedy could be and if it is just the common source amplifier or if it could have multiple power amplification stages.

3D Housing: After multiple runs through faulty 3D printing machines and a good print, I’ve determined the walls were made much too thin. I’ve thickened the walls to go from 1mm to 1.25mm and the back wall (which was thinner to account for a longer piece) to be at least 1mm now.

Printing a 1mm wall works fine, but a .6mm wall did not print anything out. Changes shall be printed out on Sunday to see if the results have changed. The picture below is a photo of the schematic of the housing, a hole at the top fit to the key switch to pop out, two sides of locking to fit the top to bottom, and a half hole through the wall for the USB-C port.

I’ve also learned VMware is much more useful than realized so that is a new tool I’ve been using.

Progress has been a bit slow. It’s been a bit frustrating as we thought buying and making changes to a prebuilt board would be easier but I see now that looking at chips like a magic box is not the whole picture. It’s important to know what is necessarily going on in each portion to gain understanding and make changes accordingly. The previous tests have mainly been checking what changes if we change what but that doesn’t necessarily add to understanding as we need to know how each different result is being made.

We completed the project! April Fool’s haha…

This week was quite a bit of debugging for the inductive charging kits, in conclusion we have determined that the kits are specifically tuned to the inductance and resistance of the kit coils. While understandably so, we have been swapping out the resistors and capacitors on the board to make our own observations on what each component has in relation to the inductance values, in which case we are quite stuck on. The board has capacitors that are not seemingly tuned to resonance so this makes it more difficult to determine what changes are needed to be done.

The inductive kits are made of a power amplifier and an oscillator, we haven’t found a direct relation as to what the changes are. We compared with sample schematics but even when replicating a schematic, it was not attuned to the stated inductance but still to the 30uH. We tested with various resistors, capacitances, and creating new coils.

We may look to buying products that fit our size, but may need to lengthen the housing more, however it would be good to have a meeting in order to sort out what could be done with the pcb kits we have.

As for 3D housing, because most of time was spent on figuring out the inductive kits, that is a bit behind, but I plan on printing the changes on Sunday. I added the top cover, adjusted the wall widths, added a USB-C hole, and compacted the width of the total housing to be thinner on one side, however, the other will stay the same.

3D housing test fitting was completed and started looking over the inductive charging pcb kits.

The fit was well and had suitable tightness for joints and solid feeling. There’s no tilt whatsoever so it’ll be good to continue the design for it. Perhaps it’ll be beneficial to have a wrist rest so users can type at a more comfortable height, however this is nothing new to the keyboard world as many users have wrist rests in order to use their keyboards that may have a slightly higher profile.

Rough changes were made to the 3D housing and we have adjusted measurements for what to change in the next print out of the housing. We shall make 3D housing changes such as a hole for the USB-C port, adjust the height, and account for the receiver charging pcb. We’ll be on track to complete fulfill the requirements for size.

Inductive charging wise, Zhejia and I have identified what is necessary to change in order to adjust the boards for our usage. We were successful removing the current coils on the boards and now going through calculations to get through the correct capacitor values to replace them. We use the reference circuits from before and are able to identify each piece well.

Next week we’ll continue the process. Perhaps a bit slow this week, but we have a plan for next week.

This week completed ethics assignment and the 3D housing design in solid works. Unfortunately, this proof does not have screenshots because I had forgotten to take them, but the files are in Box.

It was necessary to spend a while on refreshing solid works knowledge and relearning some shortcuts. I used these tutorials for guidance on snap fit joints and splitting parts

Completing the 3D housing base was relatively simple overall, however, I followed the tutorials above to ensure it would be a smoother process. Still in the progress of making the joints as there are some issues with the joint sketch and extrusion of it. Printing out the joints will also be a different thing as we will have to edit the spacing a few times to ensure a smooth fit.

We also received the inductive charging kit so next week I plan to get a prototype of inductive charging with Zhejia next week as well.

Currently this is good progress made, not stuck on thinking about what parts to buy and we can continue working towards the goal.

Q: As you’ve now established a set of sub-systems necessary to implement your project, what new tools have your team determined will be necessary for you to learn to be able to accomplish these tasks?

Majority of the week was spent on the design review reports and organizing the plan of what we had up until now. Through writing the design review, I figured out where we were in our budget which may be a concern but can now be warier of how to spend our budget. In addition, writing out the whole plan thus far helps to figure out where any more vague plans were vs. what we can easily explain was well thought out.

Afterward, I drafted a drawn plan of the 3D housing for the keys and saw what interlocking method we would use(snap-to-fit cantilever joints), and estimated the size. Overall, in order to have a snug fit we’ll probably have about 5% more room than needed from a tight fit to be looser.

I made a quick table of what capacitors would be needed to have what frequency for the inductor coils which are.

Overall some difficulties are figuring out the microcontroller next and waiting for some parts. Maybe some time crunch but now that we’re over the first half of buying items we can continue onwards.