Time to start soldering

The breadboard design testing phase is over. I'm confident I can commit some Veroboard and a few of DIP sockets to build what will be a "Double Quadruple Half-H Driver Controller" board with TTL control and 8 outputs (+ve and gnd) that can be up to 36V and two gangs up to 2A per gang.
The inputs are 8 Activate lines and up to 4 Enables plus Vcc1 & GND and Vcc2 & Gnd.
I'll keep Vcc2 on it's own socket - don't want 36V hanging around the TTL lines, so that leaves 14 connections. Just right for a 15 pin D-Sub

SO I ordered 10 male & 10 female 3.5mm jacks.

I've got some 15 Way D-sub sockets so I got a couple of 15 Way D-sub 2 row male plugs. Hopefully I'll be able to use an old VGA cable for the wire, or else some ribbon cable.

Now I need to work out a Vero board layout

I found an online tool for designing stripboard. Annoyingly you can't save it when using Firefox which, obviously, I found out after designing my layout with it. It maybe can in Chrome, I'm not sure. It says Chrome works better so perhaps this is what was meant, I haven't tried it.

Anywhere, here's a screencap of the design with some annotations.

This is the view from the component side with the tracks superimposed through. The tool lets you do it differently but I'd already done it by the time I worked that out. The tool isn't excellent but at least it did what I needed.

The beauty of doing it with a designer is that there's something to test against before adding the components, which was fortunate because I had a couple of tracks conducting when the should have been isolated.

It's taken years to get this good at soldering ;) and naturally without three hands, I managed to solder the first socket in one column of holes the wrong way and the worst way, so one of the link wires is under the small socket, no big deal.

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:

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.

Toodle Pip

The PVC tubing has arrived. It is 10mm inside diameter. I should have measured the darn pumps because although they look the same size they are, in fact, 8.5mm diameter. So I ordered some 8mm / 10mm tube which will be here next week. Good news is that it fitted the flow meters, which is the specification I took the measurement from. OOh, I happen to have a 600 L/H submersible pump with a 10mm fitting so I can commence the flow meter testing.

Timed delivery pumps on the go

The code for controlling the timed delivery of a pump is committed

Direct Pump Control Circuits

My going with dumb pump design it means more pins being used on the NXP. However we still have plenty to play with. P5-P30 on the LPC1768 and P5-P36 on the LPC11U24. The LPC1768 has three UART serial connections so I shall reserve two of those for the sensors. So to keep it to common PINS for some reason, P17-20 used for the flow restricted pumps and P5-P7 for the peristaltic pumps.

The peristaltic

The flow controlled

I made a start on the code at http://mbed.org/

For a quick test, I used this code

#include "mbed.h"

DigitalOut myled(LED1);

DigitalOut a1(p5);

int main() {
    while(1) {
        myled = 1;
        a1 = 1;
        wait(0.5);
        myled = 0;
        a1 = 0;
        wait(0.5);
    }
}

to strobe the motor.

The results were satisfying

Peristaltic Pumps

This is a quick knock up circuit I did on http://circuits.io/

The AT-Tiny uses three wires RX, TX & GND to communicate with the controller. The protocol will say which pump 1-4 and how many mL and the At-Tiny will take care of the rest. Just keep the Enable lines up, no need to for anything else as we're not changing direction or anything. I've left off the possible 4th pump as I haven't got one.

Regular pumps with flow meter

Because of varying head heights of the water storage, return from recycling, etc. issues I have chosen to use a flow meter to regulate water input. The idea being that all water input pumps can be pumping together and shut off once the required amount has been delivered. The flow meter introduces an additional complexity because the flow meter instructions say that the water speed should rise gradually and that air should be prevented from enterting the system. My pumps will be submersed so I'm not sure that will be an issue. For this discussuion that's not really an issue because that is a software problem likely to be quite simple by just modualting the control line.

The flow meter produces 1120 pulses per litre and takes a TTL supply voltage.

This circuit activates either pump, watches the flow pulses and then kills all pumps when the required flow is complete.

Decisions Decisions - Smart or Stupid Pumps?

Do I put the control next to the pumps and free up the controller to just send messages or do I keep them dumb and use the controller to do everything ?

The programmer in me wants to put an AT-TINY13 at every pump and let them do the delivery. OTOH guy says put everything in the middle because there's so much spare CPU power.

An AT-Tiny is about £1. It is attractive to me to make intelligent pumps. But it means programming the AVR and whatever I use as the controller and get them to talk to each other. But this also means that the controller can be less powerful and all it needs to do is talk whatever protocol I devise. A rich protocol, which could even be 9p, seems to solve engineering problems. By standardising with this idea I can expand the range of devices in the family as I go along. I will only have to implement the protocol on the central controller once and not care about that is attached to it.
I'm looking for excuses to make smart pumps. The action at the pump end will be the same whatever controller is used, whether it is the central one or not is irrelevant. If I start with AVR assembler to control the pumps I can always use an AVR CPU to do it and they are not rare.
There we go, that is what I shall do.