Tasmanian Racing Drone - Build Log #2
Housekeeping
This is the second article in a series of build logs I’m writing for Catalyst Machineworks’ Tasmanian V1 beast class/X-class racing drone frame. If you missed the others, follow along:
Tasmanian Drone Racing - Build Log #2 (you are here)
I purchased this frame and a bunch of components in the summer of 2019 and finally got some free time to work on this build! This is a ridiculously sized racing platform with 13” tri-blade props, 345KV motors, all running on 50V of electrical goodness.
Disclaimer: this isn’t my first drone build!
Much of this build log is a stream of consciousness as I’m working through the build - no real attempt to structure anything. While I am still in a learning mode (as we all are), I do have an idea as to how dangerous a build of this size can be. I’ll be taking plenty of precautions as I go through this, and I’ll be sharing them with you as I go, lessons learned and all. If you have constructive feedback, I would love to hear it!
Power Distribution System
With a few new orders in hand, it’s time to hook up the PDB, ESCs, and do some initial power-on tests! My current plan is to get the power distribution board soldered up, then slowly introduce voltage to the system for the first smoke test. I will eventually end up providing all 50V to the board, using my multimeter to confirm VBAT, and the 12V/5V regulators.
Quick reminder: for the latest wiring diagram, check out build log #1. Let’s start with the battery mods.
Series Battery w/ AS150 connectors
I purchased two 6S (22.2V) HRB 4000mAh 60C lithium-polymer batteries for this build. These will be combined in a series configuration to double the voltage (44.4V) which is the requirement for this build. This means that one battery’s ground terminal will connect to the second battery’s positive terminal, and this requires some special mating connector pairs. I started by laying out the connectors to determine how everything will attach, preserving ground and positive terminal identification.
There is one type of socket, and two types of plugs - one with an anti-static ring, and the other without. Careful readers will note that the two batteries do not have matching connectors!
Here’s the plan: First, I’ll need to create some harnesses that will allow me to charge these batteries on my dual charger. Second, I’ll need to convert the existing battery connectors (EC-5) to the Amass AS150 anti-static connectors. Third, I’ll need some random harnesses to convert between XT60 and AS150, and some bare leads, to conduct preliminary power on tests.
Charging Wire Harnesses
I’m specifically starting with basic wiring harnesses so I can experiment and learn how to handle these new AS150 connectors, and a larger solder tip. Before I start cutting battery leads, or soldering on 10 guage wire to the sensitive electronics, I wanted to start with something a little less critical. This will let me iterate quickly, with the least risk to the components.
Working with these AS150 connectors is a ton of fun. A 4.8mm chisel tip fits perfectly in between the hole on the barrel of the connector, allowing me to apply heat very evenly into the barrel well. I made sure to adjust the temperature of the iron up to compensate for the increased surface area, and volume of solder. One thing to note, I tinned the connector and the wire ahead of time, but fed in a lot of solder from the corner of the well. This made it a little difficult at times to verify how much I was able to flow. The solder I am currently using is 0.032in diameter, which is rather small for the size of connectors i’m working with - I wish I had something with a thicker diameter.
Battery Fit Test
I did a quick battery fit test so I can size the main power leads going to the PDB.
Main Power Leads
Next, I removed the older, stiffer, 10 guage wire that I soldered to the PDB previously, and replaced it with something nicer. This is a flexible silicone, 10 guage wire with a much higher thread count! Working with this wire is a breeze! To protect the solder joints a bit, I added some heat shrink to slide over the pad and solder joint.
ESCs
Once the main power leads were soldered on, I started working on the ESC power leads. This is where things get interesting (and crowded!). Working with these large pads, and huge solder joints, is so much fun. You can really see the joint flow!
To get the right amount of solder on these joints, I took extra time to ensure that I could hold the wire tip with my curved tweezers, that the pads had a solid support behind them, and that my solder tip was pre-loaded with a lot of extra solder. I did not want to have to feed solder into these joints and risk over heating and/or throwing solder balls everywhere. In some of the images, you’ll see that I wrapped the ESCs in kimwipes as a basic protection from falling solder - just being extra careful.
After all the ESCs were connected and cleaned, I began the final step of adding the pre-cut, pre-bent 330uF (microfarad) 50V capacitors, as required by the APD ESCs. Links to all the products (non-affiliated) are in the first build log. This required a solder tip change to something smaller. These half-cylindrical pads are pretty easy to work with. After a few attempts, I figured out that I could get the best results by placing the tip flat inside the channel, heating up the pad, wire and solder in one go. Laying the tip against the side did not work as well.
I should get some pictures of the iron placement. Maybe in a future update.
Cleanup
After all the caps were installed on the ESCs, it was time to the final thorough cleaning. I took my wire brush and more isopropyl alcohol and scrubbed all the boards, solder joints, and wires. I can be quite liberal with flux at times, and I really wanted to make sure all of it was removed before applying power.
First System Power-On Testing
With cleaning out of the way, I went through pads and joints, checking for shorts. With everything looking good, it was time for the first power-on test! Feel free to watch my incoherent rambling below, or read along for a more explanatory play-by-play. To minimize the potential for a catastrophic explosive event, I opted to supply a low amount of voltage using a bench power supply I borrowed. I turned on over-current protection as a means of protecting the circuit in case of a short.
I started by applying 5V (with a cut off at 0.5 amps of current). This is most definitely underneath the input requirements for all of these boards. Essentially, nothing happened - there was just not enough voltage to power much of anything, and only a very tiny amount of current being taken (about 50 mA). Since there was no smoke at this point, I moved into the next phase of power-on.
At 12 V, 0.5A, the supply turned on, but quickly reached the 0.5A restriction, and cut the circuit - as intended! I then raised the current protection to 0.7A, which was just enough to get the ESCs to flash their LEDs. At 12V, 1.5A cutoff the ESCs woke up and started blinking! I checked the regulators on the PDB at this point (off camera) and, as expected, they were not being provided enough voltage to step down. Makes sense… Getting closer!
At 16V, 1.8A, everything came to life! I verified the regulators on the PDB were providing 12V and 5V respectively, and the ESCs were looking good. After confirming no smoke and successful power-on of the electronics using the power supply, I moved on to test using some battery sources. To start, a used 4S battery, then a new 6S battery, and finally the series battery configuration. Everything appears nominal!
Lessons Learned
Double check thread count on wiring before purchasing.
When working with larger wire bundles, connectors, and pads, consider using a larger diameter solder.
When working with shorter power leads, cut and tin both sides of the wire before soldering to electronics. It will make the process of soldering components a little faster, with less potential to damage other electronics while you tin the cut wires in place.
Next Steps
Overall, this part of the build went quite smoothly. I’m impressed with the quality of the APD boards!
Over the next few build logs, I’ll be hooking up the flight controller, and wiring in the camera and video transmitter. The radio receiver and a beeper will follow. Of course, after all that, I’ll need to install these beautiful MAD POLARV 345KV brushless motors, and perform another round of systems testing. Flight controller configuration should happen after that.
See you on the next one.