Electric Hydrofoil - The best electronics for the job?

I wanted to reach out to the community for some guidance in choosing the hardware or micro controller for my project. I am building an electric hydrofoil and want to use an Arduino for various functions. You can search lift foil or jetfoiler for a better explanation of what I'm trying to accomplish. My question is which hardware/shields should I purchase to accomplish the following goals?

  1. Bluetooth remote throttle
  2. Voltage and Amperage monitoring of the batteries and electric motor
  3. Motor control and throttling, PWM
  4. GPS readings (for speed calculations to determine greatest distance/amps, i.e. range)
  5. Hall effect or optical RPM sensing of the propeller
  6. Sonar sensor to monitor water depth
  7. Datalogging to analyze all the above data

The system will run on 40-50 volts so I'll also need a voltage regulator.

I'd like to find the Arduino/shield which could facilitate these goals while utilizing the minimum number of components. What are the most economical pieces of hardware I can purchase that require the least integration to make this project work? Are there sensors which I noted above that are difficult to monitor simultaneously (bluetooth and GPS for example)? Are there anything else I'm not considering? Is there an specific Arduino I should use which integrate some of these needs in one board?

Thanks in advance.

Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html

Can you tell us your electronics, programming, Arduino, hardware experience?

You had better add rudder control, or direction control if you are using drive motors and want to steer like a tank or dozer.

Tom... :)

TomGeorge: Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html

Can you tell us your electronics, programming, Arduino, hardware experience?

You had better add rudder control, or direction control if you are using drive motors and want to steer like a tank or dozer.

Tom... :)

My experience with arduino is certainly not on an expert level but I have so far been able to build and understand the code necessary for a few projects I've completed including a CAN bus reader for my car, an ESP8266 wifi enabled temperature logger, and various other smaller projects. I am better at understanding the code for Arduino than the hardware required for specific project goals and it is to that end that I posed my original question.

The hydrofoil design of the project does not require mechanical methods of steering or control. Both are achieved by the shifting balance of the rider. The drive motor is strictly for forward propulsion, as can be seen in the promotion videos of the aforementioned companies, and does not contribute to the stability of the watercraft.

cessna438:
You can search lift foil or jetfoiler for a better explanation of what I’m trying to accomplish

Do you not think you are in a better postion to provide a link that explains what it is you are trying to do ?

I was not expecting it to carry a rider from the initial post. A picture is worth a thousand words.

cessna438: The system will run on 40-50 volts so I'll also need a voltage regulator.

Can you give more information on battery and motor specs ? Any other hardware you have ?

Why the remote bluetooth throttle , you will need a hardwired dead mans switch anyway

Sonar for water depth, do you have one already ? That is not a diy project.

maybe put a voltage divider before the voltage regulator. 40v to 5v is a big drop and definitely going to stress a VR.

I built a very similar system for monitoring electric go-karts. My only difference was i had no build in speed control--but I measure volts/amps/speed/motor temp, and display to an LCD and write to an SD card. Right now we're building printed circuit boards for our data logger to tidy things up. The data logger also sends the data wirelessly to the pit crew for monitoring (using something other than bluetooth). We had a ton of issues initially in cleaning up the noise from the motor, but finally got that sorted out. System works like a million bucks.

It's definitely possibly but involved, my only recommendation is to get a solder less breadboard and start building it one section at time--maybe start with measuring volts, then amps, then speed. Not sure how you will will control the motor, MOSFET's i'm sure, but that will be a challenge in itself.

Our version 1 was using arduino, but since we are displaying on 2.4" TFT's and using large fonts, we ran out of ram, version 2 is based on a Teensy 3.2 and working well.

Here is what a commercial product looks like (or will look like when it is available) |500x281

https://www.liftfoils.com/pages/e-foil-launch

If I were doing this, I would want to make the mechanical part work first, then add as desired. Motor, motor driver, batteries, arduino and a handheld throttle and wireless communication.

GPS, sonar, datalogging would be secondary tasks to be tackled after you learn to fly on this.

Have you sourced your hardware yet?

Or possibly add the instrumentation to a ready built board. I suspect the construction is likely to be the hard part.i

Sounds like a fun project! But it looks like you might be jumping in at the deep end (ObPun), I think most of those 7 items would be a decent task by themselves.

I would start with a wired throttle control, once you have that nailed you can add bluetooth, etc. It doesn't look like CPU speed will be a problem, depends on how often you want stuff updated. Probably Flash size will exceed a small AVR once you add all the features, you could relatively easily move to a Mega.

If you need to move to a faster CPU, it is doable but a lot of code depends on AVR features so porting might not be trivial. To see if you are in the right ball park, I would take the most intensive CPU feature and run a benchmark.

I doubt you will find off the shelf boards that perform all the functions you require, either way you will end up with a nest of boards. It doesn't look like there will be a huge amount of space available. You might need to think in terms of creating a custom PCB.

You also have the fun problem of making things watertight. I'm not sure how far radio propagates underwater, radio antennas for GPS etc might need to be located above the water line.

Here is a video summarizing the project: LiftFoil

A big question from the mechanical side is the powertrain. An electric motor of sufficient power needs to turn a gearbox, converting high RPM to high torque, that turns a propeller of certain diameter and pitch to achieve the desired thrust at the desired speed. As you can see, there are a lot of variables to consider. I know it seems putting on so many sensors is adding complexity early, but because the ideal motor/gearbox/prop is not common knowledge, I want these sensors to aid me in making that selection. At worst, I want the Arduino to protect me from frying the motor/batteries.

KrisKasprzak: It's definitely possibly but involved, my only recommendation is to get a solder less breadboard and start building it one section at time--maybe start with measuring volts, then amps, then speed. Not sure how you will will control the motor, MOSFET's i'm sure, but that will be a challenge in itself.

I plan on using a RC speed controller to control the AC motor with PWM and the servo.h library

LandonW: maybe put a voltage divider before the voltage regulator. 40v to 5v is a big drop and definitely going to stress a VR.

I'll probably power the Arduino from a separate 5V source.

Boardburner2: Can you give more information on battery and motor specs ? Any other hardware you have ?

Why the remote bluetooth throttle , you will need a hardwired dead mans switch anyway

Sonar for water depth, do you have one already ? That is not a diy project.

I plan to use 10-12s batteries and a 12,000W brushless in runner motor. Probably the SSS 5694/800KV and a very high amperage hobby ESC to control it.

The bluetooth throttle allows the rider control while not getting tangled in wires leading to the board. I may be able to achieve a wired connection to the front of the board but if I can make it wireless, I'd like to.

Example Wired Control

Is a deadman's switch possible via bluetooth? Such a switch could also be done via a foot strap I guess.

The sonar sensor is definitely the least required of the electronics. I just wanted a way to know if I was riding in dangerously shallow depths.

I currently have an Arduino UNO and a Mega. Also I have a EM506 GPS receiver

Seems like the foot strap switch would be easiest and most direct.

K.I.S.S as much as possible

My original suggestion was going to be a wired connection for the throttle initially, but then I thought of learning to ride this and the frequent wipeouts that this would entail. I agree wireless would be valuable. Make sure the handheld floats.

As this is something that already is meant to carry a person, there must be some form of throttle control in place. Any good reason to mess with this?

A dead man's switch is also pretty important. You don't want the board to start racing around on its own, when the rider falls off - it looks like a contraption the rider is bound to fall off sooner or later.

Many of the other functions I get - you want to know the performance of the board and so. This could be an Arduino in a waterproof box mounted on top of the board (assuming this is safe, thinking of the falls), with the appropriate sensors wired through the board. The GPS is indeed also best kept above the water for proper reception.

cessna438:
Here is a video summarizing the project: LiftFoil

A big question from the mechanical side is the powertrain. An electric motor of sufficient power needs to turn a gearbox, converting high RPM to high torque, that turns a propeller of certain diameter and pitch to achieve the desired thrust at the desired speed. As you can see, there are a lot of variables to consider. I know it seems putting on so many sensors is adding complexity early, but because the ideal motor/gearbox/prop is not common knowledge, I want these sensors to aid me in making that selection. At worst, I want the Arduino to protect me from frying the motor/batteries.

I’ll probably power the Arduino from a separate 5V source.

I plan to use 10-12s batteries and a 12,000W brushless in runner motor. Probably the SSS 5694/800KV and a very high amperage hobby ESC to control it.

Is a deadman’s switch possible via bluetooth? Such a switch could also be done via a foot strap I guess.

The sonar sensor is definitely the least required of the electronics. I just wanted a way to know if I was riding in dangerously shallow depths.

The link claims a silent motot so i doubt a gearbox is used, in any case having a custom one of those made is an expensive proposition.
Selecting the correct size and pitch of the propellor should be all that is required.
The link says the controlller shuts off the motor when 10 feet away so i suspect they are using bluetooth for this, i am used to having a lanyard attatched to my ankle which operates a mechanical switch , not sure on the legal requirments though.
You could power the arduino using a DC to DC converter , they are very efficient.

From the stated weight of the battery i assume a capacity of approx 1 KWh.

Link states a duration of one hour i assume at dawdling pace this implies a consumption of 20 A.

If you can find out how long it lasts on the foils you can better estimate the size of motor you need.
10 KW seems high to me but i just do not know.

If you had described this to me yesterday i would have been considering calling the Barmy police.
Picture was quite amazing.

Jet ski put out around 200KW but this thing has me a bit clueless.

Jet ski put out around 200KW ut this thing has me a bit clueless.

All it takes is a kite and 15-20 knots of wind https://youtu.be/hP4AcEQYi5w

Join us for lessons in Los Bariles, B.C.S. next January!

That one is still on my bucket list along with the water rocket backpack thing. :)

OP

For some idea a 5 inch ducted thruster at 1KW produces 25 KG thrust at 4500 RPM without a gearbox.

I think Speed is regulated by the water drag and torque torque is controlled by the current.

jremington: All it takes is a kite and 15-20 knots of wind https://youtu.be/hP4AcEQYi5w

Join us for lessons in Los Bariles, B.C.S. next January!

Could you give an estimate of the force on your legs when on the foil ?

or your Arms ?

Boardburner2:
The link claims a silent motot so i doubt a gearbox is used, in any case having a custom one of those made is an expensive proposition.

From the stated weight of the battery i assume a capacity of approx 1 KWh.

Link states a duration of one hour i assume at dawdling pace this implies a consumption of 20 A.

If you can find out how long it lasts on the foils you can better estimate the size of motor you need.
10 KW seems high to me but i just do not know.

From this picture of liftfoils.com we can count 196 Li-Ion cells. Assuming a 14S14P arrangement and a modest cell capacity of 3000mAh, we can assume a capacity of 42000mAh, a voltage of 51.8 (nominal) and a power of 2.175kW if they are in fact getting one hour ride times. Hydrofoils produce very low hydrodynamic drag and this is the attraction…great performance on low power.

wvmarle:
As this is something that already is meant to carry a person, there must be some form of throttle control in place. Any good reason to mess with this?

I am building this from scratch so there is no throttle control already in place. I could buy one of these but they are being marketed at $12,500!!! I don’t want one that bad but if I can build it <$2,000, I’d like to try.

bobcousins:
Sounds like a fun project! But it looks like you might be jumping in at the deep end (ObPun), I think most of those 7 items would be a decent task by themselves.

I would start with a wired throttle control, once you have that nailed you can add bluetooth, etc. It doesn’t look like CPU speed will be a problem, depends on how often you want stuff updated. Probably Flash size will exceed a small AVR once you add all the features, you could relatively easily move to a Mega.

If you need to move to a faster CPU, it is doable but a lot of code depends on AVR features so porting might not be trivial. To see if you are in the right ball park, I would take the most intensive CPU feature and run a benchmark.

I doubt you will find off the shelf boards that perform all the functions you require, either way you will end up with a nest of boards. It doesn’t look like there will be a huge amount of space available. You might need to think in terms of creating a custom PCB.

You also have the fun problem of making things watertight. I’m not sure how far radio propagates underwater, radio antennas for GPS etc might need to be located above the water line.

I plan on keeping all the electronics either integrated into the board or on top of the board in some sort of pelican case. Either way, the electronics won’t be underwater (except for the motor of course).

I should probably clear up the GPS, I know it seems like unnecessary complexity. From a standpoint of safety there is a very real chance the batteries could discharge before I get to shore. I want the Arduino to use the GPS to measure my current distance from my starting point, monitor the state of charge/amp draw of the battery and alert me when I’m in danger of falling below the electrical energy to get back. Also, I could determine the optimal speed/power (best range) and have the Arduino common that throttle setting automatically.

So if I used my Mega, and attached a GPS and Datalogging shield, would the code get too complicated if I tried to manage those inputs and outputs while monitoring the voltage/amperage, sending PWM to the motor, and perhaps lighting up a few LEDs? For the sake of argument lets say I abandon the bluetooth for the immediate future.

For further discussion on the mechanics of this DIY project check out Endless Sphere Forum

Also, there is a great guy documenting his attempt at this same project Here