A Lengthy Wrap Up

Alright this saga is getting close to caught up. Just to provide a brief, "Previously on..." I started this whole thing with the intention of bringing you up to speed with issues I was having with my speech device attached to my wheelchair. Zigzagged all over how I learned about Team Gleason, Eye Tracking technology, challenges keeping my devices powered while still maintaining mobility and left off with the longest explanation ever for how I needed new batteries for my chair. I know how you feel, because I had to wait a loooong time for my new batteries. 

So I received my shiny new Surface Pro 8 and PCEye5 from Team Gleason. But after powering the USB based peripherals (PCEye5, 2 drive control units, and a phone), the battery life of the tablets was less than optimal. Especially since I wanted to run VMs, development and RE applications, and the like. I knew I wanted to draw power from my wheelchair main batteries. These are like hard core deep cycle sealed lead based marine batteries. There's two in series for 24 Volts output. These batteries are rated for about 400 charge cycles (the number of times you can recharge, and expect decent performance). Insurance will pay for, and the manufacturer recommends replacing, them once a year. I had mine for two. At the year mark or so, we inquired about batteries, expected they were ordered, and then just went on about our days. At the time, they were still doing quite well, and I was still primarily using my Tobii speech device with the bigger battery. So it wasn't a terrible inconvenience (relative to all of the other things I have to deal with) anyway. Just shy of the two year mark, we tried again. I think the first delay was a lost order, start again. The second delay was my getting covid and having to reschedule delivery. But at least they had them. Then the tech that was supposed to come out called in sick. By now I had been waiting about two months. And the 2 year mark sailed by. I was barely making it through the day on a charge without doing much driving around or positioning in the chair. Then we heard the next tech had covid and we'd have to wait another 4 weeks for an available time slot. 

If it's one thing that ALS has taught me, it's patience. Well, I take that back. ALS didn't teach me patience, it offered me the opportunities to practice patience. Only by the grace of God, can I keep from losing my sh... cool, every moment I'm faced with being powerless to scratch an itch or a million other things that I physically can't do. This time though... I decided Jane had done more than her share of calling, being put on hold, having the call drop, calling back, cycling through the voice menus and operators that only forward you to another voice menu after asking the same questions that the voice menu did. 

Another thing my ALS has provided ample opportunity for, is asking for help when needed. I used to be uncomfortable asking favors of people. Maybe due to my feeling vulnerable and inadequate. Or perhaps just not wanting to feel like I'm the one who needs help. I should be the one helping. This was my pride getting in the way. Whatever the reason, I was done with that now. Along my journey, I had gotten linked up with this wonderful person, Kelly, who is a Permobil representative for our region. Permobil is the manufacturer of my power wheelchair. I had been in communication with her several months prior, discussing possible options for my ideas on head rests and possibly powering equipment from the chair batteries. So I reached out, the same day we got the news from the Permobil distributor, Numotion (whom I now referred to as Slomotion), that another lengthy delay was imminent. She remembered me, and after describing my dilemma, she jumped into action. There were some back and forth texts about whether I needed a home repair or if I could get the chair to the service department locally. Desperate, we didn't mind just having Jane drive the chair up there. Kelly was on the phone with the head of the service department. She worked it out that if we could get the chair up there, they would replace the batteries while she waited. Alleluia! Praise the Lord! Same day service! But He didn't stop there! 

I gave Jane a very specific set of questions to ask the technician while she was there. I've learned enough to know that many of you won't care about the details, but they were questions about power output on certain ports, and parts I needed to rig up my ideas. I just assumed that the wheelchair technicians would understand what I was asking, and that Jane would merely be the delivery person. That, turned out not to be the case. She started texting me back questions and information the guy was giving her. Jane even knew that he was not understanding my questions. It was clear that he was going to install the batteries, but that was about it. However! He did have another technician in mind that liked tinkering with wheelchair mods and that he would put us in contact. Jane brought the chair back with brand new batteries and the name of another person with whom I've come to call friend and all around wonderful human being! 

To protect his privacy, for reasons that'll become clear, I'll call my new found friend, Keith. I emailed Keith and laid out what I was trying to do. Sorry, explanation required.

Essentially, I needed to convert the 24V chair output to 19.5V for my Tobii device, and 15V for my surface pro. This is accomplished by DC to DC converters. Remember last time, I talked about AC and DC, and AC/DC? Well now you get to know why. No in depth physics this time. I just want to point out, to those of you who never read the sides of your phone chargers, why (in part) manufacturers always tell you to only use the one that came with your device, and no others. First let's clear up a misconception my kids had. The cable that you use to plug your phone into your computer to charge it, is not the charger! It's just a cable. It's a USB cable. They've had different ends on them over the years, at least the part that plugs into the phone, but they're all essentially USB cables. The USB specification includes power delivery to the USB device. It's that power delivery part that makes the cables useful as "power cables". But what about that thingy that plugs into the wall, that has a USB port on it? Well THAT'S the charger! And the side or back of every one should tell you what input  and what output power it supports. The input doesn't change, unless you have international plugs. But in the US, your standard wall outlet is rated for 120V AC. Now as we discussed last time, Nikola Tesla is one of the cool people responsible for this. As a point of fact, it was another giant of industry, George Westinghouse, who turned Tesla's AC idea into the power delivery system in America. Don't worry, no biography on him. But that little phone charger is what is responsible for converting that AC current from the wall, into a stable, and usable DC current to charge batteries, like in your phone. What does this have to do with my chair? The change in  voltage is only part of the equation in that output set of numbers. It is literally only the potential to do work. In case you're not smirking, I'll let you in on the joke. In electricity, voltage is referred to as the electric potential, as in potential energy. To do actual work requires two more pieces, the amount of electric charge flowing, or current, measured in amperes, and something to work on, usually referred to as the load, which resists the current flow and measured in ohms. I'll lightly gloss over the fact that work performed in an electric circuit is really related to the voltage drop, or difference in potential, between two points on the circuit. We're generally more interested in that change of work over time, or power, in the circuit. That's measured in watts(W). As with most units in physics, these are also named after great inventors. I'll spare their stories, although Andre-Marie Ampere should have been mentioned in my thoughts including Maxwell, as the father of classical electromagnetism. Well OK, I just can't resist the physics here. 

Only as a means to provide some perspective, I'll introduce one more term, the coulomb. Very simplistically. Hopefully. The coulomb is the unit of electrical charge. Say what? Go ahead, use that voice... You know what I'm talking about... Say whaaat? Alright, you've all heard of electrons... I hope. The electron can be thought of as a particle; a charged particle. Not in the sense of doesn't take cash, but in the sense of hair standing straight up when people are tricked into touching that weird metal ball thing in science museums (Van de Graaff generator). We have to give that charge a unit of measurement. Like distance in feet. It makes no sense to say I am 6 tall. But 6 feet tall gives you context. So the charge, as in electrons, is coulombs! Yes named after someone... Named... Chuck. De  Coulomb. Another Frenchman. Ahhhh! So one electron is one coulomb! Right? .... Errr, no. Sorry. Not that simple, but if we relate the amount of charge flowing (1 ampere) in 1 second... That's 1 coulomb! It's actually quite a lot of charge! Just to come full circle, if the coulomb represents the unit of charge, and charge comes from electrons, what does that mean? Technically, charge comes from both electrons, and the corresponding protons in the nucleus of atoms binding the electrons in orbit around it. Protons are positively charged and electrons are negatively charged. They're different particles with different masses, but in terms of charge, their magnitudes are equal, just opposite in sign. In physics we use the term elementary charge (e) to refer to the charge of 1 proton, making the electron (-1e). It's still measured in coulombs, but it's a really really really small number. So in 1 coulomb (1C), there is approximately 6.2x10^18 elementary charges! In 1 ampere(A) of current flowing for 1 second in a wire, or 1C of charge, that's like 6.2x10^18 electrons floating by! Isn't that just amazing?!? How can anybody not like physics! That's just the tip of the iceberg! 

I'm still not sure why that wheelchair technician wasn't on the same page as me when asking about power output of the various ports and the R-Net bus that connects all the electronic components together. I promise, only one more detail and I'll be done with the physics. The reason there are two pieces of information on your chargers, is that you need both the voltage and the current, in amperes or amps, to get the power rating. This is simple. 1V times 1A equals 1W. So your typical USB ports are 5V. And they can range from 0.5A to generally about 3A, for power ratings between 2.5W and 15W. But I need about 65W to fully match the chargers for my surface pro. Clearly, a simple USB port ain't gonna cut it. But this is where the DC to DC converter comes in. Specifically, a converter that utilizes USB-C ends with the USB-PD specifications for power delivery. This allows for a negotiable power synchronization to happen based on the power needs of the device. So I have a converter that will put out 15V @ 4A, or 60W. The trick is, I need 24V input from the chair. This is where Keith comes in. 

He got back to me right away. And we scheduled for him to come help me wire things up. I already had the plan and parts. I just needed someone who could speak my language with the R-Net bus on the chair and give me the two power and ground wires from the bus. This would give me the 24V input to my converter. Then from the converter to the surface pro is a USB-C to USB-C cable. The surface pro 8 comes with two thunderbolt 4 ports, which includes the USB 4 spec and can be used to power the tablet. Keith is awesome. He knew exactly what I wanted to do. But! As part of the plan required cutting an R-Net cable to expose the power wires, he didn't feel comfortable violating something forbidden while he was representing his company. His words were, "If I was coming over on a Saturday, as Keith, your friend, I would totally do it." I told him to prepare everything else, and I would take care of the wire. I had Tina, an aid that comes on Tuesdays help with that. She loves working on projects with me. All the stuff Jane hates doing with technology. It worked great! Keith and I became fast friends as I filled him in on the stuff I was working on. We traded personal cell numbers and he said just text me if you need anything. I'll take care of it personally. He even loaned me a piece of equipment that only dealers are supposed to have access to. It's a programming dongle that unlocks full access to any programmable part of the R-Net system that runs the chair. He "accidentally" left it behind. And then "was too busy" to retrieve it for a few weeks. Even after he got it back, he would drop it off on his way to or from work whenever I wanted it. He is still excited to see what I've done to my chair and was available next day during an emergency ripping out of much of my electronics off the back of my chair when cables got caught in the door as it shut behind me. He made a few trips off book for me to help wrangle boxes and wires. Even though I've since been able to attain my own programmer permanently by another channel, he still will come at a moments notice. 

So that wraps up the chair stuff for the computer and eyegaze and all day power untethered to outlets. Now I get to bring you up to speed on the really cool stuff! I'm tired of typing for now, so peace friends! And stay tuned.