Domestic Data Acquisition System ideas (for heating parameters)

[Vortex3]

Hello,

2009 New Year resolution is to implement a Heatbank, and also solar HW.

Ahead of this I am thinking of a project to put together some kind of data acquisition system for heating related parameters.

I would like to be able monitor:

• Various temperatures (eg indoors, outdoors, hot tank x 2, solar input/output temps etc )

• Digital events (thermostat demand, boiler on/off times)

• Pulse trains (eg possible flowmeters)

This could be autonomous or possibly PC based (I have a Windows Home Server that is permanently running). In either case I would like to be able to get the data into some kind of tabular form for analysis every now and then.

I want to do this on a sensible budget. There seem to be several possible approaches:

• Use "Home Automation" components such .............But expensive and I don't actually want to automate or control anything.

• Use home weather station components such as available from ...............But all rather bespoke and again pricey.

• Use something like the µChameleon from ...............Appears to be just the job hardware-wise and sensibly priced (about 50 quid on eBay) >BUT< I do not want to write software if I can avoid it. I am emailing these guys anyway to see if there is 3rd party software support that may be interesting.

Q. Is anybody out there doing this kind of thing? If so how? Any other ideas?

david

[Dave Liquorice]

That certainly covers a good number of digital and analog IO for your PC but I wonder if it's wise using a PC as the control system, particulary one doing other things as well. Fine for non-critical monitoring and production of stats. For control I'd be tempted to look at a PLC of some sort.

You are looking at a bespoke system so I don't think you'll be able to avoid doing the software as well, the chances of someone else having done just what you want are remote. There might be something similar that has been published that you could modify does that count as "writing software"?

You can get commercial solar controllers but I know very little about them. Having data available must be a fairly common request so I'd expect to find some of them with data outputs, maybe only at the top of the ranges though.

[Andrew Gabriel]

I rolled my own about 8 years ago. At the time, I was out of the country a lot of the time and wanted to keep an eye on things remotely, and turn the heating back on ready when when I arrived home. I've done this in 2 houses now.

To give an example, here's a log (of the heating related events) for a period when heating is in setback mode (12C downstairs,

11C upstairs). There's also monitoring of things like fridge and freezer temperatures, but these generate lots of output as the compressors cycle on and off, so I've stripped them out here. (The Bedroom 3 and Outside readings are just recorded for information, whereas the Downstairs and Upstairs readings are controlling the heating demand in their respective heating zones to maintain the setback temperatures.) 13:39:04 Temperature - Downstairs 12.5 13:49:46 Temperature - Downstairs 12.0 14:07:42 Temperature - Outside 4.0 14:55:43 Temperature - Outside 3.5 14:57:35 Temperature - Downstairs 11.5 14:57:37 Output Downstairs Heating Demand ON 14:57:56 Input Boiler Burner ON 15:09:31 Temperature - Downstairs 12.0 15:09:33 Output Downstairs Heating Demand OFF 15:09:34 Input Boiler Burner OFF 15:31:41 Temperature - Bedroom 3 11.0 16:14:15 Temperature - Outside 3.0 16:15:23 Temperature - Outside 3.5 16:21:23 Temperature - Outside 3.0 16:52:52 Temperature - Downstairs 11.5 16:52:54 Output Downstairs Heating Demand ON 16:53:12 Input Boiler Burner ON 17:05:06 Temperature - Downstairs 12.0 17:05:08 Output Downstairs Heating Demand OFF 17:05:09 Input Boiler Burner OFF 17:30:13 Temperature - Outside 2.5 18:09:28 Temperature - Bedroom 3 10.5 18:42:13 Temperature - Downstairs 11.5 18:42:15 Output Downstairs Heating Demand ON 18:42:33 Input Boiler Burner ON 18:55:08 Temperature - Downstairs 12.0 18:55:10 Output Downstairs Heating Demand OFF 18:55:10 Input Boiler Burner OFF 19:01:13 Temperature - Bedroom 3 11.0 19:25:59 Temperature - Bedroom 3 10.5 20:28:48 Temperature - Downstairs 11.5 20:28:50 Output Downstairs Heating Demand ON 20:29:08 Input Boiler Burner ON 20:33:33 Temperature - Upstairs 10.5 20:33:37 Output Upstairs Heating Demand ON 20:39:09 Temperature - Bedroom 3 11.0 20:40:33 Temperature - Upstairs 11.0 20:40:36 Output Upstairs Heating Demand OFF 20:43:05 Temperature - Downstairs 12.0 20:43:07 Output Downstairs Heating Demand OFF 20:43:07 Input Boiler Burner OFF 20:43:38 Temperature - Bedroom 3 11.5 20:49:28 Temperature - Bedroom 3 12.0 20:49:51 Temperature - Bedroom 3 11.5 20:52:07 Temperature - Outside 2.0

[MM]

It depends on how practical you are, whether you can assemble rudimentary electronic circuits, do soldering, that kind of thing. Or whether you are all fingers and thumbs when it comes to DIY. I built a solar water heater last "summer", using copper tubing from B&Q painted matt black and mounted inside a large wooden box, also painted matt black. On a really hot day I could easily get enough water for a shower by later afternoon. Trouble was, and the reason I placed "summer" in quotes, we got very, very few days like that in 2008! Hopefully, 2009 will be warmer.

The size of this "panel" I constructed is about 1m x 0.8m, but it could be made much larger, or more panels made, plus more tubing. The heat is there for the asking on hot days! Leave a water hose on the lawn for a while, then turn it on and feel the water coming out. It will often be more than hand hot. In the states they put coils of hose on the garage roof specifically to heat water for domestic use.

Anyway, as I was talking about electronics, you may wonder what this has to do with a DIY solar water heater. Well, the principle by which it operates is the thermo-syphon principle. Classic cars with no water pump are a good example. The hot water would rise and circulation established. However, as the car manufacturers found, I also found that a small pump would boost the circulation a tad, so I bought one from a ship's chandler (it's the kind that is used to pump out bilges). It's only about 10cm long and 3cm in diameter. But I couldn't just switch it on and forget it. So I bought a timeswitch kit from Maplin that allows the time to be controlled very precisely. You can set DIP switches on the circuit board for the switch to come on for precisely 20 seconds every 15 minutes. I believe you ~can~ buy switches like that commercially but they are very expensive compared to your typical domestic timeswitch bought from Wilkinson or B&Q.

Now, if you are "in tune" with all the above, you are in the right frame of mind for experimentation! If not, I would get a man in to do it. That is likely going to cost a great deal of money, however. How long will you need to run the equipment before it has paid for itself?

MM

[Vortex3]

[snip]

Can you tell me more about the hardware. I'm curious!

[Vortex3]

Hello Dave (and MM)

I don't think I was sufficiently clear.

My intention is to use a commercial off the shelf heatbank; solar bits and controls. Probable suppliers are:

DPS for the heatbank (GX family)

for the solar components and controls.

This will be a self-install some time after Easter.

I most certainly do not want to have a PC involved in the control. Just to acquire a bunch of data!!!! and hopefully assist me in measuring the efficiency and tuning the overall setup. My experiences wiith Windows media Center have taught me absolutely not to rely on anything with Windows for domestic applications.

From the web site the µChameleon from

would appear to have some autonomous capability....and even do some control....but that MIGHT be for phase 2!

To be honest I think I'm going to buy one of these Chameleon things and see if I can rediscover my programming skills (last used 0.25 centuries ago).

I just downloaded Microsoft Visual Basic Express (free would you believe:

). If I can make the hardware do what is claimed with this then I think that would be a good start! But I think I need to consult with a Software geek friend of mine to make progress.

David

[Dave Liquorice]

I didn't look that closely but if it can be made to store readings and be kicked into spewing them out when a host computer asks for 'em that would be useful. Saves having to have a PC on logging the data and the risk of gaps if(when) that PC crashes.

As for programming my server is Linux based and I'd be using Perl/PHP/GNUPlot.

[Andrew Gabriel]

It looks like it's the sensing you're interested in, rather more than the control.

For the temperature sensing, I use the Dallas/Maxim DS18S20

1-wire sensor. It's a digital sensor and bus interface combined, so you can string a whole load of them on a single data bus around the house and address them individually. They look like tiny transistors, but are actually 3 terminal IC's. They have a parasitic power mode where you can power them from the data line, in which case you just need a single twisted pair to interconnect them all (although parasitic power mode isn't recommended for higher temperatures as they draw more power at high temperature and may run out of stored power when sending back the data).

You need something to interface the Dallas 1-wire to a PC or whatever. I use the modules built by Peter H. Anderson

which provide a serial port interface to the devices, and simply return the temperature in °C from each DS18S20 it finds on the bus. Other people also make 1-wire interface cards/modules.

You can obtain temperature to 0.5°C resolution from the DS18S20 chips. They are actually significantly more accurate internally, but it's quite a bit more complicated to read the extra digits, and most 1-wire interfaces don't do so. There's additional functionality in the DS18S20 which I don't use, such as the NVRAM and the ability to program it to perform the role of a simple thermostat.

The serial interface connects to an always-on PC which does continuous monitoring and control of the house. The software is my own and has grown over the years. As someone else said, I wouldn't run this sort of thing under Windows. It's run under Solaris x86 (unix), where uptime is limited only by power cuts, which is typically in excess of 2 years, and if anything else were to go wrong, I don't end up stuck with a non-functioning box showing a blue screen of death when I'm 8000 miles away.

[meow2222]

Whatever you do, just bear in mind the system will be running long after today's computers are gone. hopefully for several decades, and you need to cater for hardware to run it for that long. There are a few possible ways to do that, just dont overlook it.

NT

[Geo]

I have been doing some data collection for a few weeks to tweak our (fairly standard) DHW. I started with the windows program from here:-

uses some DS18B20 temperature sensors (from Farnell) and a simple

5-component interface to a standard RS232 serial port (details also on the site).

I have 5 sensors connected - the advantage being that only 1 wire (ok 2 including ground) is required from the PC to the sensors. I used some old network coax.

[RaRaRa]

control

Like others who have replied, I monitor temperatures at various points in my house (garden, kitchen, hot water cylinder top, central heating primary loop, etc) using some Maxim DS1621sensors. They cost about £4 each from Farnell, and you'll need to build a small circuit costing about £10 to interface them to a PC's serial port. Some example links:

[Vortex3]

Interesting. Thanks for that.

I'm going to stick with analog inputs for now the more I read about these µChameleon thingies the more curious I become....so I am definitely going to pick one up.

Will also get some LM35's

and some instrumentation wire....hopefully will be able to get some logging going pretty quickly.

I have a feeling that rediscovering BASIC will keep me off the streets.

David