SteamyTea

Why are we discussing architects? we have a habit of chasing them away on here

Proper Cornish then me hansom

Just logging around the house, so cables would be no more than 10m long, probably a lot less. I was doing it with DHT22/11s, but the 11s proved unreliable and inaccurate (I do have some more 22s which seem much better, must rig some up and calibrate them). It would be nice to use very cheap equipment if it proves accurate and reliable, I seem to have reliable code (and simple) for my logging now, just a matter of time to see how reliable it all is.

The more I read about the two systems, the less I like them. I had read about the cable limitation on I2C, seems a good reason to avoid it for household data collection. It may be easier and cheaper to use a Zero with an ethernet adapter, would still be under 17 quid for 4 sensors. I shall try something out soon, just got a very busy week this week as I have a show at Land's End starting Friday for a week (kitchen table is full). All bad timing.

Terry I may not have made myself clear. I want to connect 10 of these to the RPI, and have a reliable RTC as well. Ideally, they will be on the same bus as that leaves RPi pins free to do other 'stuff'. Maybe they are not what I need for this project, just that they are ridiculously cheap and I keep reading that up to 128 of them can be connected in parallel. There seems loads of examples about using just one of them via the I2C, very little about using them via SPI, and then there is confusion about which bus protocol to use (some say you can connect two, others say up to 128, some say only on SPI, others say on I2C, all very confusing). There does seem to be a way to read them using the CSB, set it high and it is locked out, set it low and you can read it, I think. But this uses up GPIOs on the board, which is what I am trying to avoid. I can see why 1-Wire is so sensible, a nice easy address (shame you can't put your own name on it i.e. living room instead of 28-0516b2b58bff).

Lovely, I shall fall asleep reading that.

I have bought a few of these nifty temperature, humidity and air pressure sensors: http://www.ebay.co.uk/itm/302009695856?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT How do I connect they to a Raspberry Pi Model A so that I can read from all of them. I have an real time clock (RTC) already connected to the Inter-Integrated Circuit ( I2C) pin, and as I want to use several of these to check temprature and humidy, I need to run then via the Serial Peripheral Interface (SPI). I am struggling to find much about it from the hardware side, so uncertain as to how to wire them up. They have 6 pins (once soldered on): VCC = power GND = ground SCL = clock SDA = data CSB = ? SDO = ? I think that CSB may be the 'polling' pin to read from that device and SDO may be the data pin. These seem easy to set up on I2C as it only uses SCL and SDA as far as I can work out, but, as mentioned earlier, really struggling to find anything about setting them up on SPI.

If you are designing/building a custom control system, is it worth making sure that basic off the shelf controllers can be easily fitted if needs be. So take a room thermostat. It is fairly easy and cheap to design one that can control a switch with great accuracy (even add in weather compensation) and log data (and even publish that to a website). If in years to come, someone else needs to change that controller, it would be good that they can go to B&Q, get the most basic mechanical thermostat and just wire it in. Some marking up of cables would be necessary i.e. power to controller, control lines, but all cabling should be marked up anyway. Maybe something worth thinking about.

http://www.telegraph.co.uk/news/2016/09/10/keith-vazs-wife-says-i-forgive-him/

What kind of freight goes in your trains, is is a lot of domestic refuse?

Nor does the Fat Controller But you might get this:

Jeremy You could totally redesign the lawnmower. All that research you did at Culdrose should come in handy. Probably best to wait till Now 5th for the initial tests. You would also find out how strong the window film is. Just think, you could 'mow' the lawn from several thousand miles away

Should really be repeated about 20 times though (not that I think it actually matters for these). Until an experiment has been repeated several times, it is hard to know if a run was a fluke, or a true reading. 20 runs and you can get a confidence of about 5%.

I thought it was Ada Lovelace that was the mother of computing. I am personally not interested about the legalities of copyright and patents, that is for people that lack imagination. I developed a plastics system that overcame a problem, tried to sell it, no one was interested. So quite happy to take that to the grave. Not as if it is life changing, unless your boat or aeroplane fails. Much more interesting what you can do with 'others' inventions. I once bit a chunk out of my tongue, took about 3 weeks to sort itself out. I am still careful when I eat anything chewy.

I found the ones I got were very good. If they are made under license, I can't see any reason that they should be worse than US made ones. US made ones probably come from China anyway.

An RPi model A. I made up a connector with a bit of vero board and some terminal blocks, plus a resistor. Shall post up a picture when I get home (up your way at the moment).

That is a good thing. At that price, a quick calibration check and throw out the bad ones is all that is needed. May even drill a long hole in the floor for one.

May order some when I get home, good price.

Can't open the link

I did some training for ASLEF once, got to 'sit with the driver'. Fascinating journey. 110 MPH does not seem fast from the cab, the signals appear quite quickly and, at the time, the driver had to swap over safety system. Much more complicated than I ever imagined. Then there are the track sitters to deal with, not something I could cope with.

I think the easiest and cheapest option to fit PV would be to make up your own frame to take regular modules.

You may be able to get a small air to water heat pump that can suck out a few kWhs of energy at the right temperature, and if it can modulate low enough, could be used to control the overall temperature in the conservatory. It does mean that you will be having a few tonnes of outside air coming into the conservatory every day, which may have an impact on the rest of the house. I don't think there is a simple and cheap DIY method to do it. You may be better making the overhang out of PV modules or some ST panels and just use the electricity/thermal energy to heat the water in a cylinder and contribute to the ASHP running (make/buy a diverter). You will possibly find that your overall heating costs are pretty low, say less than £250/year. Water will probably be half that, so with those low levels of spend, the concept of return on investment becomes pointless (I spend more on going for a coffee each week than I do on my energy bills).

I picked up some clear drinking straws yesterday, they look the right diameter to stick the DS18B20s in, so just need to get some silicone.

As I had a couple of hours free yesterday and my 9 DS18B20s had been running a couple of days, I thought I would look at how precise the readings where. I cannot really check accuracy as I do not have a calibrated thermometer to check them against. So what I did was to create a range of temperatures that are imaginary true ones. Then look at the spread of readings in each bin range. This is pretty easy in a spreadsheet, just list a range of temperatures (I rounded down to 1 decimal point the lowest temperature then incremented up by 0.1°C). Then I looked at means between the the bin below and the bin above i.e. Temp bin below < DS18B20 reading > Temp bin above. This makes for a very quick visual comparison in a spreadsheet as the DS18B20 mean should be pretty close to the "imaginary" temperature. Some numbers are going to follow now. If I take the minimum temperatures recorded by all sensors first. 14.6°C (Imaginary), 14.72, 14.71, 14.69, 14.70, 14.75, 14.71, 14.75, 14.75, 14.70 Then the maxium 24.4°C (Imaginary), 24.50, 24.51, 24.50, 24.51, 24.51, 24.47, 24.47, 24.47, 24.52 Then the highest overall count (this gets really nerdy). Sensor 1, Count 528, Imaginary Temp 18.3, Mean Temp 18.30 Sensor 2, Count 517, Imaginary Temp 18.2, Mean Temp 18.20 Sensor 3, Count 480, Imaginary Temp 18.2, Mean Temp 18.19 Sensor 4, Count 526, Imaginary Temp 18.2, Mean Temp 18.19 Sensor 5, Count 542, Imaginary Temp 18.2, Mean Temp 18.19 Sensor 6, Count 559, Imaginary Temp 18.0, Mean Temp 18.01 Sensor 7, Count 579, Imaginary Temp 18.4, Mean Temp 18.37 Sensor 8, Count 579, Imaginary Temp 18.4, Mean Temp 18.37 Sensor 9, Count 638, Imaginary Temp 18.0, Mean Temp 18.01 So it seems that these cheap DS18B20s are pretty precise in the temperature range I have so far tested, not more than 0.15°C out, which is neither her nor there for what we are using them for. I have also not had any errors in the 11,166 readings I have taken over the last couple of days. I am sampling every 13.59 seconds overall. I also had a look at the standard error of the mean, but that is really so low that it is not worth mentioning, but I will anyway 0.03°C max. Now to really go overboard with the stats, I also looked at the median and modal values. The biggest difference from the imaginary temperature was 0.1°C on the modal values (as expected as there are not many readings, but not counted them.) The main thing here is that all the values are very close together, between -0.09 and 0.10°C over a range of 10.2° shows that the logged temperatures are pretty well normally distributed. This is a good thing when testing, as more accurate assumption can be drawn. Not sure what conclusion can be drawn from this, apart from the precision of these very cheap sensors is plenty good enough for me.

If you call a landline from a VOIP phone, what number is displayed? I ask this as I use a call blocker on my mobile, stopped my Mother calling as she had a masked number (until I unmasked it so she could call her mate).