I think I fixed the reset problem

I added a NAND gate to the circuit and put it inline with the enable signal for the pump driver. This prevents the pumps engaging when the controlled is reset.

Something like this:

Tank connections and 80 micron mesh ordered

To join the tanks I ordered 4 Overflow Tank Connectors 22mm

This has a 22mm thread on it, which is the same as the one that a washing machine uses.

So I ordered some 80 micron stainless steel mesh

after seeing some filters built into 22mm washers for washing machines.

Consequently I have also got some 22mm connection tubing

Growing tanks acquired

I got a couple of plastic containers to use as growing tanks for an ebb & flow setup from Wilkos. It says £5 there, it said £ on the shelf in the store but at the till they were £3.99

The plan is to pump water from a store into one of them through 10mm pipe and have a 22mm overflow connector feed the second one and another 22mm overflow exit that one and return the water to the store. This means that the containers won't overflow.

A second overflow connector in the bottom of each one container will feed into the solenoid valve I ordered yesterday. This will be activated for the drain cycle to make sure that the water stock is completely removed. The water removed in the drain cycle is filtered through an 80 micron passed into the recycling phase where nutrients and pH are set to appropriate levels and other processing such as uv exposure for removing biological pathogens such as pythium can take place.

Separating the flood store from the recycling phase means that the pH and ppm probes can be utilised across multiple growing areas. The probes are the most expensive parts of the system so this reduces costs when scaled. The UV can also be used across growing areas.

The tanks and connectors in the "grow room"

First controlled flow.

I got my first reading from the flow meter. The instructions reminded me to use the pull up resistor. The code is a bit basic.

Octave code for plot
times = [ 66.192 67.180 68.180 69.180 70.180 71.180 71.280 72.180 72.280 73.380 75.180 75.480 76.180 76.580 77.180 77.680 78.080 78.780 79.080 79.880 80.080 80.980 81.800 82.080];
ticks = [ 34 101 105 750 833 836 846 847 862 921 923 942 944 964 967 1018 1021 1072 1075 1132 1137 1196 1200 1266 ] ;
plot(times, ticks);

This isn't the best data but it's late and I want to go to bed. It's supposed to start with a low flow and then get to a steady state, this is to prevent the flow meter being overwhelmed. I'm sure at this flow rate that there is no real danger of that but it was the right idea to start with.
The k-factor is 1120, that is 1120 ticks per litre. Next time I shall see about measuring amounts.

Solenoid valve ordered

I have ordered a normally closed, 240V solenoid valve with 10mm pipe connections - datasheet

The device was £19.99; ex VAT but eventually cost me £31.08 included VAT and delivery.

Making danger

Putting yesterday's bits together. I have the relay gaffer taped into a pop bottle and the pump sitting in a 25 litre bucket. I have checked that the pump runs from energising the relay. All good.

Time to write to code for the NXP. First off for sensor testing purposes is to get the TCP / IP running. The simple UDP sender already found a checksum bug in the supplied library. Oh well, at least the packets still show up in Wireshark. Let's hope TCPSERVER on Linux will ignore it.

Off to Wickes / B&Q now to find some plumbing bits.

Ready to get my feet wet

I bought a 12v relay from Maplin that will switch 240v to power the pump I have with a 10mm outlet. I have wired it all up and tested the switching action. Success. I've put pins on the flow meter (snipped LED legs) and made signal cables for the relay with more pins from an old Nokia power supply that had an inline step-up adapter.

Luckily I had a 3 pin mains socket, they wanted over £ for one in Maplin. Mine still has the 99p sticker from Wilkos.

That means I'm ready to start pumping some water.