Hey Electrified Miata team, here's the latest update in the never ending quest to go faster, have fun, and be safe! For those of you following along, last week, the goal was to verify the display technology's ability to run on the Pi, turn up the Kart performance, fix the relay dropping out problem as well as publish our current software on Gitlab. However, I fell short on publishing our software but we did get the rest of it done, and the results were exciting in three different ways. I'm thinking we all could use a little excitement that doesn't stem from endless barrage of Covid-19 news.
On Monday, I had just gone to the grocery store and was feeling a little depressed at some of the panic buying. In the past, when feeling at little blue, I'd take the Pantera out for a cruise and it never failed to either put a smile on my face and/or give me something to focus my efforts on. The raw rumbling power of 500hp would set you back in the seat and make your heart race. With the Pantera gone, I decided the go-kart could possibly take its place. With the cell testing complete, I invited Bruce over to turn the performance up. Bruce has the software to turn the performance up on the motor controller via a Windoze machine I choose not to have. We were able to turn the performance up! A little experimentation let us set the throttle rates from 5 to 10 out of 15 and turned the performance control from 20% to 50%. Bruce took it out for a quick test spin in the cul-de-sac and immediately I saw Usain Bolt in the 100 yard dash. However, the connection issues between the Pi and the relays reared its ugly head rendering another vexation, giving me something to fix, while still making me smile.
To fix the connection between the Pi and the the relay box, the plan was to use a Pi i/o extender as shown below
However, some of the wires refused to solder, even after dipping them in rosin. It's been a while since I've experienced that level of frustration soldering. I've been soldering ever since Dad got me a soldering iron at age 10 and I can still hear his instructions on how to solder, but it just wasn't working. How can this be? I've never had this problem before! Finally I tried a different set of wires and everything went fine. I'm guessing the alloy was somehow different or there was a coating on the wires preventing the solder from adhering. Very strange. With the connection fixed, there was only one thing left to do, test it!
Since the kart will now get more use, I built a ramp so we can get it in and out of the garage easily instead of getting stuck on the lip between the the driveway and garage. Yes, the kart is that low. The next rendition will have more ground clearance. This was the first time I had driven it with the new settings. I saw Bruce drive it and it looked like it had quite a bit more performance. There is nothing quite like that push from behind that keeps coming strong, till the wind starts to roar and you have to squint. Oh my, this was so much better. Borrowing a line from Ford vs Ferrari, where Ken Miles gets his first taste of a 427 and exclaimed, "more of that please". With all that acceleration working strong, stopping suddenly became a new top priority. I thought "oh my" again, but in a completely different tone, carefully calculating the distance between the nearest objects to hit and the pitiful rate of descending speed as the rear tires struggled for traction. I'm seeing disk brakes up front in the future. Then I discovered the main battery wires dragging on the bottom.
This time the phrase "oh my" is said with raised eyebrows at the trouble that this could have caused. I could imagine fire, smoke, and a melted Kart. At least I'm well stocked on cable and connectors, and it couldn't have happened at a better time given all the world events taking place.
With a possible 'shelter in place' order, I picked up the all-thread from home depot, and went to Ed's shop to cut them down to size. The parts I needed for the second battery arrived and I'll be working on that this week. Installing a second battery will require disassembly and re-wiring parts of the kart. A second battery also means we'll have the capability of getting enough voltage to possibly make a Leaf motor spin!
Joe's been quietly building BMS boards so we'll be able to charge our packs and keep the cells healthy. We've ordered Anderson Powerpole connectors for the mini-pack. I've been amazed at how much vibration there is on a running kart. I have a new appreciation for the "goop" used in automotive products to hold everything in place. I was able to verify our display technology choices indeed runs on a Pi. I've been working on more software in the background with two goals. One to be able to cleanly separate projects from the supporting infrastructure, and two, being able to start and stop project software in sequences. This will be used to make sure the power controls are started before the display is enabled. We aren't meeting in person due to the current Covid-19 situation but we are also investigating have some YouTubes made to fully describe the hardware, software and driving the kart.
The goal for next week is the get the current kart software published on GitLab and to get a second battery pack operational. That may be ambitious, but I have all the parts in house. Thanks again for reading.