On 5 February 2013 23:49, Tim Brocklehurst <t...@engineering.selfip.org> wrote: > On Tuesday 05 Feb 2013 23:25:15 James Courtier-Dutton wrote: > >> The 1 wire therm is a good idea. The fewer moving parts the better. >> With therm sensors rather than on/off at particular temp, i can make the >> heating system better. I.E. When in heating hours, heat normally, when out >> of heating hours, make sure the system does not freeze. I don't need to >> adjust the heating with a stat dial on the wall, i can use a smart phone >> app. >> I still wish to detect 240V AC because that will help with fault finding. >> The system could do analysis for me and tell me which part has failed. I >> think the ADC would be good for that. >> Example diag: >> 1) Turn burner on and send heat to the HW. If the HW temp does not rise a >> bit, something is wrong in that part. >> 2) If the burner is on but the HW temp is still falling. The sensor is Ok, >> but something else is faulty. >> 3) If different power is sent to the diverter valve, does the orange output >> change as expected. Points to working valve or not. >> 4) Measure current and volts to the pump. A pump should always draw a >> predictable amount of current when on. If not, faulty pump. > > Have a look at: > > https://github.com/TimB- > QNA/Electronics/tree/master/RaspberryPi/InvestigationBoards/SPI_ADC > > I will add some code to read/write all the stuff on that board at some point > (all written as it is, just not tidy!). You can adapt pretty much everything > there for your purposes. > > Given that the DS18B20 has a unique ID per chip, you could also use them > locally around the boiler. >
Thank you very much for this. With regards to the SPI_ADC, I like it. As I will be doing ADC on Mains input voltage, I will be adding a digital isolation on the SPI bus. E.g. ti iso7241 So the ADC will be on the 240V AC side, but then the raspberry PI will be protected by the digital isolation by having the isolation on the link between the ADC and the PI. ADC -> Isolation -> SPI Bus of PI. This also improves the accuracy and simplicity of the ADC side, no isolation transformers, and uses less power to measure it. -- Please post to: Hampshire@mailman.lug.org.uk Web Interface: https://mailman.lug.org.uk/mailman/listinfo/hampshire LUG URL: http://www.hantslug.org.uk --------------------------------------------------------------
