T100 Stretch Goal #1: Check!, Stretch Goal #2 Announced!!
We blew past our first stretch goal in just over 48 hours! You guys are absolutely amazing and we are ecstatic about the support that we have received so far. Since we reached $40,000, every thruster reward level will come with a free mounting bracket with each thruster. Here's what it looks like (this is real life, not a render):
STRETCH GOAL #2: Integrated ESC at $65,000
As promised, Stretch Goal #2 is AWESOME and will change how you use the thruster. It's an integrated electronic speed controller (ESC) that is highly compact, water-cooled, and perhaps most importantly, has PWM and digital I2C input signals.
If we hit $65,000, then the BlueESC can be included with any thruster or OpenROV reward level for only $45 each and to any BlueROV or SolarSurfer reward level for only $25 each (since they come with basic ESCs already). If you already added $20 for the basic ESC, you can switch to the BlueESC by adding $25 each.
Here's what the ESC looks like (it goes between the nose cone and the rest of the thruster):
We custom designed the BlueESC specifically for underwater use. It's sealed in a blue anodized aluminum enclosure that also serves as a heat sink. The enclosure is the same diameter as the core of the thruster and it fits right between the nose cone and the thruster. It connects to the thruster with three simple solder connections. If you buy the BlueESC and thruster together, we'll do the soldering for you. If you want to upgrade later, it's simple to connect the ESC yourself and we'll have instructions available.
Although we designed the board ourselves, it is heavily based on several existing ESCs and uses an Atmega8 microcontroller and SimonK tgy firmware, which is used on thousands of ESCs for airplanes and multicopters. We've been talking with SimonK himself to make sure we've got everything figured out. We use pressure-tolerant electronic components so that the ESC can handle significant pressures just like the thruster.
Wiring With The BlueESC
We think the coolest thing about the BlueESC is how much it simplifies wiring on your vehicle.
For example, without the BlueESC, you have three wires per thruster that have to pass through the hull of your vehicle. If you only have 1-2 thrusters, that's not a big deal, but if you have 6, it's a pain and it makes it hard to replace a damaged thruster or move thrusters to a new vehicle. Besides that, the ESCs take up space and generate heat inside the hull. Here's what that looks like:
With the BlueESC, you have two signal options. The first is a regular PWM signal like any other ESC. You need one of these per thruster, so to connect six thrusters, you have power (battery +), ground (battery -), and six PWM signal wires. We've made a Power/Signal Junction Board to make this as easy as possible. For each thruster, you solder power/ground and the signal wires to the board and then a single cable containing all those wires goes through the hull of your vehicle. A removable conformal coating, like liquid electrical tape, protects the connections from water. Easy! Here's a diagram of the PWM signal connections:
The second option is I2C, which is even cooler. If you're not familiar, I2C is a parallel addressable digital bus communication system. Basically, it means that the ESCs have "addresses" and you can send them messages to tell them what to do. Most microcontrollers, including Arduino, Raspberry Pi, and BeagleBone have I2C built in. Connecting the thrusters through I2C only requires four wires total: power (battery +), ground (battery -), and two signal wires for I2C. With those four wires you can control up to 128 thrusters, which is way more than any sane person would want, but think of the possibilities! Again the Power/Signal Junction Board makes it really easy to connect a bunch of thrusters and have only one cable going through the vehicle's hull. Here's a diagram of the I2C signal connections:
One of the coolest things about this is that you can use high-quality underwater connectors. Underwater connectors are expensive (like $50-$100 a pair) but if you only need one of them instead of a bunch, it's reasonable to use them and stay on budget. Cool!
Power/Signal Junction Board
The Power/Signal Junction Board will be included for free if you buy more than one BlueESC. You need it to connect multiple BlueESCs together outside the vehicle so that one one cable goes through the hull. We'll have more details in the future.
BlueESC Specifications (In Progress and Subject to Change)
- Diameter: 40 mm (1.6 in)
- Length: 13 mm (0.5 in)
- Material: Blue anodized aluminum
- Potting (sealant): Thermally conductive, vacuum degassed potting compound
- Maximum Depth: TBD, but it will be significant
- Voltage: 6-16 V (2-4s lithium polymer battery)
- Max Current (in air): 20 A
- Max Current (in water): 30 A
- PWM Signal: 5V (1100 us: full reverse, 1500 us: stopped, 1900 us: full forward)
- I2C Signal: 5V (protocol details will be published later)
Other Important Things:
- The ESC is reprogrammable through the signal cable
- The BlueESC will be completely open-source, including schematic and board layout
We'll have more details on the BlueESC and the Power/Signal Junction Board in the future.
Risks and Schedule
We've been planning the BlueESC for a long time, and we've done a lot of research, designing, and some prototyping, but it is still very much under development. Because of that, we're going to give you a few options in terms of schedule:
1. Choose to have your thrusters ship on schedule followed by the BlueESC approximately 2 months later. You'll have to connect the BlueESC to the thruster yourself. It's pretty easy.
2. Choose to have us hold on to your thrusters for an extra two months and ship them after we integrate the BlueESC. (Recommended)
Presuming that we make it to the stretch goal and we're able to build the BlueESC, you will be able to choose which option you want after the Kickstarter. If you choose not to get the BlueESC, you will still get your thrusters on schedule!
There's a little more risk involved with the BlueESC since we haven't gotten as far in the development process. The next section below talks about why you should trust us to get it done!
Why You Should Trust Us To Do This
The BlueESC is obviously a totally different beast than the thruster when it comes to design, testing, and manufacturing. Here's why you should trust us to make a product like this as well:
- We're all mechanical engineers by training, BUT two of use have spent most of our careers in software and electronics
- We've built brushed motor control boards in the past and understand the basic challenges of power electronics
- Collectively, we've designed over 40 electronic boards and have had hundreds manufactured. Most of these have used the same microcontroller and many of the same components. We are familiar with the assembly, testing, and troubleshooting processes.
- Our design is HEAVILY based on existing and very well proven ESCs. We're not trying to reinvent anything, just package it better.
- The firmware that we will use is the best and is the industry standard for multicopter ESCs.
Remember, the BlueESC will only be available if we can hit $65,000 total. Don't add the money to you pledge for the BlueESC until we pass that point! Don't worry, we'll make it very clear when we've passed the stretch goal and remind you of all the options.
As if this isn't enough, we have another awesome stretch goal in the works in case we make it past $65,000. It's a *big* deal. ;-) Stay tuned!
While you're here, add us on Twitter and/or Facebook!