Sending sensors to the depths

Latest update August 18, 2015 Started on January 2, 2015
Bob is an open source, buoyancy controlling AUV and sensor platform or, to put it another way, he is a little robot that can sink to the bottom, float to the surface or attempt to maintain a specific depth in the sea - and carry a set of sensors.

January 2, 2015
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In The Field

We hit the Dublin Make event at Trinity College, Dublin in late July - still not sure I've 100% recovered from the experience...

Due to ferry issues it ended up being a mad dash / trip and we managed to travel through 5 countries in 36 hours to manage it - leaving England late Friday evening, travelling through Wales then catching the late ferry to Ireland - arriving at and attending the event on the Saturday, mad dash to Northern Ireland that evening, late ferry to Scotland then driving back down to England on the Sunday (and sleeping most of Monday).

We took the Iron Man Lego ROV and fish tank to keep the children entertained, and three Bobs for the more serious side of things.

We were swamped from start to finish, had a lot of interest and a lot of questions ranging from "How does Bob control his buoyancy" through to "Why is Iron man driving an ROV when his suit works underwater".

Thankfully the weather remained sunny and we even managed a quick drink in Temple Bar before leaving.

I would say that we now have event attending, set up and pack up down to a fine art. We've come a long way since Birmingham earlier this year.

Next update will feature the new Bob designs, I've moved away from the acrylic dome for the new version - it was proving a bit too restrictive for the little benefit it provided ( somewhere to put lights and look pretty ) and as I've now "mastered" the art of bonding PLA to acrylic the flexibility of a more useful top dome / payload area is difficult to resist.


Another long period with no updates, but a lot of activity, so apologies for the long report.

I'm continuing to make updates to Bob - though I have a backlog of parts to 3D print - thankfully all the new parts for the 3D printer have now arrived (after its attempt to melt ) and I've almost completed the rebuild so I should be able to get them going this weekend.

I've jumped versions forward to Mk3 (Mk2 is now the version with modifications that we took to Maker Faire UK) as it has new end caps and finally switches to the closed-circuit buoyancy control method.

I'm also going to start experimenting with the viability of long-range wireless transmissions for when satellite isn't justified / affordable - also looking at GSM. We'll be able to test these later in the summer when we head off for remote deployment testing.

Deployment training

Back in the Kayaks this weekend, now we can safely sit-on a kayak we're moving to sit-ins this weekend - sit-ons are nice when the weather is warm and sunny - we don't get that much in the UK so some level of protection is needed, sit-in kayaks give us the ability to go out in a wider range of weathers, though deployment and recovery may be slightly more of a challenge - once this weekend is complete we head to sea the following weekend to learn how to tackle waves and stronger currents.

Educational Outreach

We were at the inaugural Liverpool MakeFest in late June, whilst we could take a Bob to sit on a desk we weren't allowed a deep tank to have him diving as it took place in the central library - so we worked something else out :)

We ran a couple of workshops on building an ROV using Lego and then using them to recover pirate treasure. It actually worked very well and we were swamped with attendees - as a workshop the aim was to teach ROV control and the concept of weight, trim and buoyancy and get people interested in underwater robotics. Off the back of this I've now released the designs and instructions for the Lego ROV should anyone want to run their own workshops / build their own ROV.

Adopt a Bob - to get ready for the new term (after the school holidays here in the UK) and to get away from referring to the current Bobs as Bob One through Four, we're asking schools to name a Bob - we'll then work out some workshops and remote skype chats as their Bob is deployed and show them how to track them online.

Dublin Maker

We'll be in Dublin at the end of July for the Dublin Maker hopefully with the first Mk3 Bob and some Lego ROVs, if anyone is nearby then please do come and say hi.

That's all for now - I'll be posting up some more updates as Bob Mk3 goes through his soak test.

Some links for things mentioned above

Liverpool MakeFest write up 1 -

Liverpool MakeFest write up 2 (apologies for the grinning buffoon, it's not the best picture of me :( ) -

Adopt a Bob -

Lego ROV instructions -


Another weekend and more practice on the water. This time it was deployment and recovery practice with a weighted demo Bob.

We're definitely getting the hang of Kayak control and balance now, though we are still in a relatively sheltered environment - the big test will be over the summer when we head to the lakes.


How are you dealing with currents? Just a GPS ping when they return to the surface?

Yeah, these we had set to ping and strobe LEDs on surface - current wasn't that bad really, so had a bit of a paddle about and then waited :)

For stronger currents / larger areas we'll be more reliant on the GPS message coming through to us for recovery.

Summer is almost upon us and we're getting closer to deploying some test Bobs around the UK.
Some initial deployments will be around the Lake District in the Northwest UK as there are quite a few quiet locations to run tests and a few of the lakes are deep enough to really push things.

However, whilst Bob is probably up for the challenge - his handlers aren't, so we took to the water this weekend for a kayak initiation session to see which styles would be more suited to our needs and to learn how not to fall off them.

Weather permitting we'll be doing some deployment and recovery drills next weekend and maybe move beyond basic paddling / splashing.


Safety first! In US waters there's an almost free online course to get your 'boaters certification' card. It's now required for all boaters. Is there similar certifications available in UK?

Exactly - there are no mandatory courses here, but it certainly makes sense to spend some time with experts and learn as much as we can.

There are RYA courses available for power and sail boats. The powerboat course is the next step for us I think ( plus the VHF license just in case ) - but first things first :)

Slightly delayed post as my other life got in the way :(

We hit Maker Faire UK on the weekend of April 25th / 26th with a smaller stand than we had at the Big Bang Fair, this turned out to be a wise move as the only means of accessing water was via repeated trips to the kitchen with buckets - how we'd have managed with the large tank I simply don't know (well, I do - we wouldn't).

The Maker Faire was a lot more relaxed than the Big Bang Faire and I think as a means of encouraging children into STEM subjects it does a better job than the more corporate Big Bang - I'll certainly be shifting to do more Maker Faire type events than regional Big Bangs now I think.

I've put some pictures of the stand up over at the Dark Water site -

Because of the more relaxed atmosphere I had the time to have some nice long chats with quite a few people there, most of whom pointed me in the direction of other people I needed to talk to :)

Robin Fearon, a local journalist, wrote up a nice post about the project as well -

So, all in all an interesting weekend.

Bob Updates:
- I've been redesigning the endcaps over the past few days to get rid of one of the most annoying / time consuming parts of the original design - I'll be cutting these this week and putting them together for testing. If all goes well then it will make assembly and servicing a whole lot easier.

  • firmware updates - I'm currently working on mission storage / parsing / remote updating code - Sending individual messages via the internet / twitter is fine for demonstrations but longer term mission plans (and the ability to change them mid mission) are needed for the real world.

  • Bob board mk2 - next step is to update the Bob processing PCB so that it has the Micro SD card slot built in and the ATTiny85 on board as well. The ATTiny85 will handle the interface with the Iridium satellite modem - it basically gives us an extra serial port as well as an external monitor to keep an eye on the status of the main processor if needed.


I've been a little bit quiet recently - work for Maker Faire is moving forward and we've about 4 and a half days before we have to load up the van and head east to Newcastle.

After successfully blowing up our 3D printer the modifications to Bob have been limited to what we managed to get printed prior and modifications / updates that only required soldering, programming and laser cutting.

We'll have two functional prototype Mk2 Bobs with us, so can judge on the direction to take based on which modifications perform the best.

Work on the integration and fit of the Iridium satellite modem has started - due to a lack of Serial ports on the Spark micro controller (we need at least one for the GPS and one for the modem) I'm going to have to modify the controller boards to fit in a small attiny85 to add additional serial ports and send them to the Spark via I2C - so that's for Mk3.

I'll update once we are at the Maker Faire - fingers crossed the Wifi is capable of allowing our Twitter interface and the web-cam this time.

If anyone is visiting Maker Faire then please pop over and say hi - look for pirates and you'll spot us...

This morning I finally got around to uploading the Laser cutting, 3D Printed and PCB design files on to the Dark Water Github - along with the cut down Spark Core firmware we used at the Big Bang Fair.

These are for the Mk1 "Ides" version we took to Birmingham - I still have to complete the BOM and put some instructions together - but at the moment I recommend NOT building this version.

The niggles and annoyances we came across putting together and deploying the Mk1 should be addressed (or the larger ones at least) in Mk2 which I want to get complete for the Maker Faire in April. So I'd recommend holding off until that version at the very least.

The repository for Mk1 is here -

Work on Mk2 begins this weekend.


The Big Bang Fair 2015 is now over - it was a long week and I honestly have never been this tired in my life.

Thousands of school and college children visited the stand over the initial 3 days, played with the ROVs, asked interesting questions and rapidly understood what Bob was and how they would use him - we had a lot of "That's so cool" responses and my explanation and story telling abilities got better as the week progressed, though my voice got considerably worse. I now think I'm in a few teachers bad books as I sent a lot of groups of children away to nag them into letting them build underwater robots in class.

Saturday was different as it was open to the public and we got a lot more families and youngsters who were more interested in the Open Source side of OpenROV and Bob.

Questions were more technical but just as interesting and hopefully we've inspired a lot more people to take a look at underwater robotics.

Bob managed to surface and dive nicely - unfortunately the hall was saturated with smart phones trying to connect to wifi so we were unable to get the Twitter controlled part functioning very well (the tank cam was pretty much a still frame so had to be abandoned) so I switched one of the Bobs to run a dive / surface / flash lights cycle to show off the functionality.

What have we learnt?

There are quite a few improvements and changes that need to be made to make the use and deployment of Bob a lot easier - an example of which is to place an on-off switch somewhere that can be accessed without having to take the entire electronics shelf out of the pressure container :)

Work begins on this after a few days rest ( and design uploading to Github ) and should be ready for the UK Maker Faire in late April - onwards and downwards.

Photo below is of Martin Evans discussing Bob and a little bit of microROV and Bob surfacing video.


It looks like it was a success! What about using a small magnet and a reed switch to enable/disable your BOB? This way the electronics will stay dry. My dive flashlights work on this principle. I’d imagine you would have to embed the magnet in a slot into the general body of Bob so it doesn’t get knocked off by accident.

A magnetic switch is a good idea, that's exactly what SeaBird and other CTD manufactures use on their equipment.

Yes, thanks both, I think magnetic is the simpler option (and simple is best) - will take a scan and see if I can find more info on other implementations and go from there.

@rocketman - I'd class it as successful :) As a learning experience I've come away with a lot of information from what, is technically, Bobs first deployment - mk2 will be a lot better because of it.

Also, engaging with so many people, both young and older, has shown me that there is a genuine interest in the oceans and seas and the technology being built for them (maybe a bit skewed towards the positive because the UK is an island ). If nothing else it's inspiring :)

Late response, but I went with the magnetic switch idea - new design now has a space for a magnet to be slotted in and held in place. Whilst it's not a genuine on/off switch ( Bob remains in deep sleep until the magnet is in place and then wakes up / remove the magnet and he switches everything off and goes to deep sleep again ) it works very well - out of the water s far anyway :)


We arrived at the NEC in Birmingham for the Big Bang Fair 2015 yesterday afternoon and have been setting up the stand and tank ready for the show to open tomorrow (Wednesday), with a little bit of time to do some Bob testing.

So far testing has gone well, with Bob Three getting a lot of attention from venue staff.

Looking forward to the show now, I'll hopefully get a live webcam up and running so that Bobs can be controlled via Twitter from anywhere in the world, but it's late now and I need sleep :)

Picture of the stand and a video from the tests attached - more soon.


I love the treasure chest. nice touch!


you had mentioned being able to send Bob commands via twitter, is that set up yet? I'd love to try it when it's beta!!!

Hi Erika, the aim was to switch that on and use it this week but the WiFi in the conference centre was that saturated today it proved unworkable and the webcam was down to a frame a second :(

Going to see if we can sort something as we go on and will post as soon as we are up and running - at the very least we want to get the tank feed running.

We are connected to the world again - the nice man from British Telecom arrived, messed around in the junction box for a bit and seems to have worked out the issues!!!

Now for some rapid firmware updates, a lot of testing and the switch on of the Bob cloud ready for the show - it's a lot of work to fit into a small amount of time but certainly doable.

The fantastic Andrew Streett and Swift Engineering have been life savers and helped enormously ( taking a lot of stress off my shoulders ) by 3D printing some of the larger, more time consuming pieces of Bob on their large 3D printer.

Each part of the battery compartment was taking over 6 hours, and constant monitoring, on the small printers I have access to - so the offer of help was really appreciated, and rapidly taken up :)

That, and the moral boosting skype chats have certainly kept the project (and me) on track :)

The parts have come out really well (image below) and also help to alleviate the niggling doubts I had about everyone else being able to build their own Bobs with just the digital files.

The PCBs arrived this morning and are already soldered, I'll post an update of those soon.

I can finally see the light at the end of the tunnel - Bob (one to four) will live and be controlled by school children with smart phones in exactly in 14 days - we're hoping to get a live feed up and running so stay tuned for updates.


Love the prints. I suppose the lateral voids are for batteries, and the central is for electronics?

Lots of progress - very few updates. We are still without internet access at the HQ, so the whole "Twitter controlled Bob cloud" part of the development and testing has been slow to non-existent - hopefully we'll be connected very soon and then can push forward with that part.

A stripped down BobOne did some manually controlled bobbing in the bath last week, I'll have to re-test with the full contents, but I think I've got the required ballast calculations sorted now - and there is enough room to remove ballast to add extra circuits and sensors.

As time is increasingly getting tight, we've moved forward with the Bob production line and all hands are busy gluing and soldering everything we can before the PCB boards arrive (hopefully today or tomorrow).

More soon, and some video, when the bandwidth to upload it is available :(


The second attempt at a 24hr soak test ended last night and was a huge success - absolutely no water ingress at all.

I've already incorporated some modifications in to the designs for the end caps and now the process of laser cutting these for "bobtwo" and "bobthree" begins.

Next steps are to complete the soldering for the prototype, get the fully assembled unit weighted correctly and in for a full test and finish the PCB designs and get them off for manufacture.

It's 26 days until the Big Bang Fair, so time is getting tight :)


This is looking really good! Way to go!

Last night we set up for a 24 hour soak test of (as the testing prototype is now known) - unfortunately it ended after about an hour when dampness was spotted on the kitchen roll based water ingress sensor.

It looks like the dome on the initial end cap wasn't cemented fully. This has now, hopefully, been rectified and I'll be carrying out an initial dome submersion test tonight - after which we'll go for another attempt at a full 24 hour submersion.


A large part of the past few days / week has been spent re-vamping the battery power supply for Bob.

I originally wanted to use the same size batteries as OpenROV uses (26650) - primarily to have some form of cross-over between the two systems. Then those with an OpenROV and a Bob would only really need one collection of batteries and charger.

Unfortunately, despite a lot of effort and CAD wrangling I just couldn't get the fit right so have had to shift to 18650 batteries instead. An advantage of this, though, is that we can fit a lot more in and so, hopefully, get a longer lifespan.

The new battery holders will allow the use of between 4 (2x2) and 12 (6x2) batteries to provide the roughly 7 volts of power we need, and depending on the mAh of the batteries - something like 21,600 mAh - with a little bit of rejigging I could possibly fit another 4 (2x2) batteries in there - but that is for later.

The structure of the new battery holder means that different batteries and sizes could be used in the future, it would just require new holders to be printed and slotted into place.

The image below is of the first battery holder in mid-print - one of these packs sits on either side of the inside of the pressure tube, with space for the buoyancy tank (and extra bits and pieces) in the middle.


Looking good! Can't wait to see the initial tests!

The first big deadline for 2015 is to get a few Bobs ready for the attending school children to play with at the Big Bang Fair UK in early March.

To make things a little bit more interesting, and interactive, these Bobs will respond to commands sent via Twitter - the Twitter monitoring being done by a Node Red server before sending the command off to the targeted Bob.

For extra "flashness" I've built a small Dome payload with two sets of LED arrays (one white, one blue) and the GPS - as well as adding something extra to control, the aim will be to see how well (or not) the Bobs could be used as a light source / beacon and how well the GPS works in the Dome without an external aerial - though testing indoors in a convention centre probably isn't the best for this...

As a side note - technically these initial Bobs could be commanded anywhere in the world - as long as they have internet access, and depending on timing / progress I may try to send one or two away to places and point web cams at them - I'll keep you posted if I need volunteers with tanks :)

Updated - now with added video - it's a bit shaky as I'm holding the camera in my left hand and typing API commands with my right - commands go via the "Bob cloud" and back to the micro-controller which then operates the lights.

Expedition Background

The aim of this expedition is document the prototyping and testing of Bob, our diving open source sensor platform.

Bob is an open source, buoyancy controlling, vertically traveling AUV and sensor platform or, to put it another way, he is a little robot that can sink to the bottom, float to the surface or attempt to maintain a specific depth in the sea - whilst carrying a set of sensors.

Because Bob is an open source project, the hardware designs and software will be available to anyone who wants to make their own Bob, improve them or modify them to better fit their needs and uses.

He is designed to be made with cheap, easily obtainable, hardware and Laser cut / 3D printed parts and, importantly, be configurable for a wide variety of needs. Our aim is to remove as many of the barriers and costs as possible for deploying an individual sensor or network of sensors underwater.

Bob can be set to stay submerged for a period of time, either at a set depth or on the bottom, taking sensor readings before surfacing for recovery.

Alternatively Bob could be set up to function, like he is in the video, as a monitor so that a sensor reading within a certain range will make him surface and report - e.g. a reading on a hydrophone that could signify boat traffic in an area where they are not allowed.

We are currently prototyping small Bobs and plan to get them deployed in a few locations for testing early this year as well as getting them in schools and colleges to encourage an interest in STEM (Science, Technology, Engineering and Maths) and the Oceans.

Our Bob entry won the BLUE ocean conservation grant competition late last year which has really helped move things forward to the point where we are finalising the build of Bob One for testing in the next few months.


This is wonderful, I look forward to seeing how well the platform performs and what you discover. Where can we find the open source plans if we want to look into building one?

Hi Erika -

Thanks, hoping for some interesting times :)

All the designs, files and firmware will be added to Github as designs and prototypes move forward / prove not to be disastrous.

Initial (early) repositories are on there now -

Should hopefully have something more than a holding page for the website soon as well - so that will link to all the resources.

Very cool! I can't wait to see this in action!

Looks like a very interesting development project, can't wait to see how it turns out for you guys!

Looks great wishing you all the best in it's development and interested to see the way's it grows and changes with time

Great idea. And the platform coul easily be adapted from traveling vertical to horisontal, i.e. towed behind a boat. Looking forward to see how the project unfolds.

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