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FishPi | One Year On.

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FishPi | One Year On.

Postby FishPi » Fri Mar 15, 2013 2:25 pm

FishPi; the POCV & the Sea.

March the 4th marked the one year anniversary of FishPi’s inception (link). When I began the project I had the optimistic expectation of being on the high seas by now. That hasn’t happened, but the optimism is still there. FishPi will cross the Atlantic, it might just take a bit longer than I expected!


So what has happened over the past year?

The Proof-Of-Concept Vehicle (POCV) is finished, just about. On board is a Raspberry Pi attached to a GPS, Compass, Temperature Sensor, Adafruit’s 16 Channel PWM, a USB Webcam, and just recently a USB Wi-Fi Dongle & a RockBLOCK Satellite Communicator. All of that, with the exception of the Compass & Webcam, resides inside an upturned plastic lunchbox.

The accompanying Base-Station began as simple screen-in-a-case with a keyboard which plugged into the POCV making it simple to manage the craft, but the original thought of using a 32-Core cable umbilical between the POCV and the Base-Station proved to be a bad idea. Too many complications and too much interference meant the system was removed.

Now inside the Base-Station are another Raspberry Pi, a USB Hub, and a 4-Port Wi-Fi Router. Adding a Wi-Fi Link opens up the possibility of real-time remote control using xrdp & the FreeRDP client, this should enable a live video stream out the world over the internet. Hopefully during testing we’ll broadcast some live video, certainly some photographs from the on-board Webcam if nothing else.


We’re also well on our way developing the Command & Control Software for the POCV.

The POCV’s Command & Control system has been coming on strong. Having begun with almost nothing, Al Gray has done a fantastic job integrating the Compass, GPS, Temperature Sensor, Rudder, Webcam, and the Electronic Speed Controller into the C & C software. At this stage he has coded for manual control; forwards, backwards, Left & right. We can drive the POCV remotely using the Webcam as a visual guide, but it has only been done in the bath so far (link)! The Command & Control software is available via GitHub at (link).

Still to come is the automation. We’d like to be able to give the POCV commands and then leave it to go do its thing. We’re using the GeoTiff file format for maps and GPX files for tracks, routes, and waypoints.

Another major function is telemetry. The RockBLOCK Satellite Communicator (link) enables the POCV to have two-way communications where we can receive information back from the POCV, and of course relay commands to the POCV too.

What about the Atlantic?

While all the building and tinkering has been on the POCV, our ultimate goal of crossing the Atlantic still remains.

Behind the scenes I have done a fair amount of research putting together a plan for the FishPi Prototype, I’ll give you a brief run-through of what I propose;


The Hull.

The exact shape, and dimensions for the FishPi hull are still very much open to debate. I have based my current ideas on the proportions of the solar panel.

Given that the vehicle is likely to capsize in rough seas it would be silly not to have a self-righting mechanism. I was trying to avoid a keel simply because I didn’t want it to foul up with detritus from the sea. Due to the shape of the solar panel I have had to add in a keel to stabilise the vehicle.

To make space for the trolling motor I cut out a section of the keel, and added in an extended flap which will become the rudder. The keel will help give some protection to the trolling motor, and I envisage reinforcing the keel’s leading edges to strengthen against and collisions. We can also add instruments to take environmental measurements to the weight-bulb at the bottom.

Materials I expect to utilise are autoclaved carbon fibre, Glass-Reinforced Plastic (G.R.P.), and Kevlar.

Solar Power.

Since the very early days of researching which solar panel to use I have always claimed the Enecom HF 130 (link) as the best. I have still not been able to find a better suited off-the-shelf panel. Weighing at only 2.2kg and only 1.7mm thick the HF 130 should give plenty of power while not adding too much weight to the topside. The HF 130 produces 16.89v at 8.1A during peak efficiency. The Panel will be attached to a watertight removable hatch on top of the hull.


I found trolling motors by chance; whilst searching for low powered motors I saw a photo amongst the images of ROV thruster & Azipods. At the time I disregarded them as I wanted to develop our own hub-less rim thrusters. A few months later I returned to trolling motors after following some advice from a man in the know. The model I am considering is the Minn Kota Saltwater RT55/EM (link). It features a 12v 50 amp motor with a Weedless Wedge 2 Propeller. While this motor is for saltwater there is an almost identical, cheaper, freshwater version. Both versions are DC brushed motors.

Mtroniks make a 75 amp brushed DC speed controller (link), the unit is waterproof, small, and can operate at 12v.



To keep the electronics dry we’ll put them all inside Pelican cases (link). If any water does seep inside there will be bags of silica gel to absorb any fluids. High density self-expand foam will fill all empty areas inside the hull and around the Pelican Cases. Connections between any cases will be sealed with IP68/IP69K plugs & sockets (link).

Solar Charge Controller.

There are two options available. Firstly we can have an automated system, but this gives no indication of batter power levels, charges rates or otherwise.

A good example of an automated controller is the Landstar LS2024RP Solar Controller (link), this particular solar charger is compact and waterproof. The downside of course is the lack of monitoring.

An alternative controller, with monitoring, is the Tracer 2215RN (link).

I am for the moment still unsure on which route to take with the charge controller. Finding the right model with monitoring is proving harder than I imagined.


We have several options available including Sealed Lead Acid (SLA), Nickel-Metal Hydride (NiMh), Lithium Polymer (LiPo), and my current choice, Lithium Iron Phosphate (LiFePO4, LFE).

In case we lose the FishPi I don’t want to pollute the seas or lakes with toxic batteries, so SLA and NiMh cells are not an option. LiPo cells can be unstable causing excessive heat leading to fires, so we are left with LiFePO4 cells.

I have found a 3.2v 200Ah Prismatic LiFePO4 battery (link). FishPi will use four arranged in series giving a total storage capacity of 200Ah at 12.8v, or 2560 watts.

Back-Up Batteries.

Having experienced the consequences of a power cut and the subsequent data corruption on the Raspberry Pi’s SD Card, FishPi will be using an Uninterruptable Power Supply (UPS). OpenUPS by Mini-Box (link) is an intelligent UPS, and using a USB cable we can interface a Raspberry Pi with the UPS giving total control of power regulation for the electronics package. OpenUPS supports LiFePO4 batteries, a separate cell (3.2v 40ah) will power the electronics in cases where the main power supply has failed.

I am considering the possibility that we may use the OpenUPS as the main power controller where we connect the solar panel directly to the UPS. This will mean doing away with the charge controller altogether. If a separate solar charger is to be used we will be able to monitor power consumption, battery levels, and other details with an array of additional sensors.


We’ll have two Raspberry Pis on board; splitting the navigation & power management away from the metering equipment & communications.

The RockBLOCK (link) will manage long-range two-way communications. We’ll be able to issue commands and receive telemetry data from the FishPi. We’re also looking into monitoring AIS shipping information so we can send course corrections to help avoid collisions (link). Wi-Fi will manage short-range communications to the FishPi. Sending a command via the RockBLOCK will enable/disable the Wi-Fi link.

I’m very interested in fitting a YellowBrick v3 (link). It can operate independently of any of the Raspberry Pi’s. It can report its location automatically at set intervals, and it has its own power supply. I think it would be wise to have one fitted in case we have a total system failure. We would be able to monitor the FishPi’s location even if we are receiving no telemetry via the RockBLOCK.

In addition to the required GPS, RockBLOCK, and Wi-Fi, the FishPi will be able to take environmental readings, take photographs, and record video.

I am still no closer to finding a solution to transmitting live images back from the FishPi whilst outside of mainstream data communications.

The Coming Year?

Expect so see the POCV on a larger area of water than what’s inside my bath. We’ve been given the run of the Bournville Model Yacht and Power Boat Club (link), so we’ll be testing there in the coming months.

The main focus after the POCV is the Prototype, primarily the hull design. I like the size and shape of the concept above, but it might not be well suited to the open seas.


A Ginormous Thank You to Al for his work on the software!

A massive Thanks to everyone on the Supporters Page, without your help FishPi wouldn't be much more than a thought.

Lastly a big hug for everyone else!
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Re: FishPi | One Year On.

Postby nabberuk » Sat Mar 16, 2013 9:58 am

looking good :)

be careful with the size of the keel (surface area of the keel side). if its too big in relation to the size of the hull you'll get lots of sideway action from the currents etc.
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Re: FishPi | One Year On.

Postby FishPi » Sat Mar 16, 2013 11:26 am


I'm hoping that by having the large gap in the middle for the motor that there shouldn't be too much side movement. It is only the first concept design so there will be some changes to come.
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Re: FishPi | One Year On.

Postby nabberuk » Sat Mar 16, 2013 10:24 pm

ah cool, what did you use for the cad drawings?
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Re: FishPi | One Year On.

Postby FishPi » Sun Mar 17, 2013 12:15 pm


I used Autodesk 123D Design (link) to draw up a quick concept.

Attached is the .123dx model file. The model is released CC BY-NC-SA 3.0
(1.86 MiB) Downloaded 1232 times
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