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About This Blog

This blog was started to serve as a record my university work back in 2009, in the 10 years since I’ve improved a lot and what’s shown here isn’t representative of my current work. I’m leaving it as an archive in the unlikely event any of it proves useful or interesting to someone.

I hope to occasionally post updates for various projects time permitting.

Last Year’s Problems

Something I was hoping would be cured after rebuilding was the bug where the Arduino would appear to crash and lose all its target values causing the system to drain. Unfortunately the problem is still there but since everything is more robust and better thought out I will hopefully be able to figure out the cause.

So far I have found that it doesn’t happen when power isn’t being supplied to the pumps and valves and it looks like the pumps are the main culprit which is odd as it should be isolated on the relay array. A separate power supply for the pressure sensors also doesn’t help. Right now the only thing I can think of is that the pressure sensors are right next to the pump motors so they could be picking up EMF and tripping the Arduino.

I could do with an oscilloscope.

Putting Canute back together

After wiring and plumbing everything the next stage was to put it back in its housing, attaching the pressure sensors and wiring everything together. IMG_20140711_193043This time more of the power circuitry is inside the unit so only the 12V supply, single 5V supply, 6 control wires for the pumps and valves and the 3 pressure sensor data wires are external. After testing all the connections and relays I could then start the attaching the lid and tubes.

IMG_20140712_144416

After putting a little water in each of the tubes I was happy to find that everything appeared to be working. The self priming pumps took a little while to start moving water but when they did, they moved it nice and quickly. The pressure sensors needed a bit of calibrating because they were not positioned the same way as before.

Not finding any leaks I made the pumps fill the tubes as far as they could with the water already in the system and then filled it the rest of the way, the theory being that there physically isn’t enough water in each tube’s reservoir to overfill the tube, even if everything goes horribly wrong with the control system.

Wiring the Relays

It’s taken a while but I’ve finally gotten around to doing the wiring for the relay array. This involved striping and tinning wires to stop them fraying in the screw terminals. The wires I am using are much higher gauge than they really need to be for the 12V 2A maximum going through them.

Relay wiringThe original pumps I used had spade connectors but unfortunately the self priming ones I have don’t so I’ll be getting some when I get the chance, I want to make it easy to swap out parts and avoid having anything soldered when it doesn’t need to be. I’ve also connected a pair long wires to the main power terminal to take it to the external power supply.

IMG_20140706_165439The valves appear to do what I want and have been attached to the pumps, I’ve placed them before the intake so that water remains in the pump and means it doesn’t have to self prime but can when it’s first turned on.

IMG_20140706_171717I checked my solenoid valves and found that they still had water in them after a year and that the hose fittings had corroded slightly and stained the tubes. I drained them and thankfully they still worked. I’ll have to make sure I remove all the water from it when it is not in use.

After getting and fitting the spade connectors my next concern is with the plumbing and how to make the most of the space provided by getting rid of the hand primer pumps and how to wire the three pressure sensors. I’ll probably also have a look if there is now a better way to send control signals to the Arduino from the net.

The Tide

Something that was unexpectedly difficult for me was calculating the state of the tide as a percentage so I decided to post what I came up with in-case someone needs it.

It takes one of the day’s high tide times and the time you wish to know the percentage of, both in hours.

public function get_level($high, $time){
    return cos(pi()/6.2103 * ($time - $high)) * 50 + 50;
}

Parts

The 3 new self priming pumps were the first to arrive, the ones I ordered cost £7.12 each, have a max current of 1.2A at 12V which is less than the old pumps, hopefully without a significant loss of ability to move water. One thing that I wasn’t sure about was if the the pumps already incorporate a one way valve to prevent water flowing backwards though them but after testing I found that it would be necessary so I’ve ordered some.

parts

The second thing was the new relay array for controlling the 12V supply for the solenoid valves and pumps which tidies things up and reduces the amount of soldering. The pressure sensors will be part of a separate circuit board.

Along with the valves I’ve also ordered some more 6mm PVC tubing. With the time for orders to arrive and without any hard deadlines and the inevitable flexibility of self imposed deadlines progress is slow but I’m hopeful it’ll be functional fairly soon.

Canute 1.2

The first complete Canute which was presented as my final year project made use of ultrasonic range-finders to detect the water levels in each reservoir and therefore infer that whatever water wasn’t in the reservoir must be in the tube. This worked to a point but since it was only measuring over a 10cm range in the reservoir and the range-finder was only accurate to 0.5cm there were only 20 points along the display tube which it would come to rest. Additionally the ultrasonic range-finders were sensitive to water droplets on the mesh in front of the detector and contact with them and the internal shelf they were on made them temperamental. Another problem was that each of the electric pumps it used required manual priming with hand pumps. This was all manageable but it did require baby sitting.

For the degree show my project would have to be left alone for extended periods so I decided to use the week between the hand-in and the degree show to upgrade it to make use of water pressure sensors instead of the ultrasonic range-finders. I was pleased with their performance, however since I only had the two I had to wait till the day of the show opening to get the third and fully test the system.

Unfortunately something went wrong on the main relay board controlling the centre tube and something was causing the Arduino to restart, I had a spare Arduino which still crashed, the code had not changed significantly and nobody could identify the cause of the problem. It was a bit disappointing especially since it had been working. Canute was living up to its name, but it was still good to have it at the show, despite the problems.

I hate leaving things unfinished.

Now there is nothing at stake I’ve began the process of redesigning the electronics and ordering new parts to get Canute working again. The plan this time involves self priming pumps which means I’ll no longer have to worry about pumps running dry or have to lift the tubes in order to prime them. Not having the hand primer pumps taking up room will also be helpful.

Instead of using the circuit boards I soldered myself I will use a prebuilt relay board and also include the Arduino inside the unit. Instead of the lab power supply I used before I’ll use a more compact laptop charger type one which might also be able to fit inside. Ideally I will also include an Ethernet shield so all you have to do is connect the unit to an internet connection and power and it could fetch tidal data that way.

Then of course it’ll be time to start Canute 2.

After University

I’ve not been posting since I finished university and started working at Silverstream TV, but I do plan to continue working on Digital Art and Technology style projects and posting about them here.

Now that I don’t have deadlines to work to I’ve ordered new parts for Canute and will rebuild it again to be faster, more accurate and much more robust.