Nickfromwales Posted July 6, 2017 Share Posted July 6, 2017 Ok. I tried a pipe stat on the 22mm hot water supply to the current bathroom job. Idea being it was a quick and basic means of detecting heat ( eg someone running the bath / shower / basin ) so that would bring on the large mirror demister pad. Crap hysteresis and pretty unreliable. Question.... How much additional electronics are involved to just make the cable off to a thermistor instead and have that operate a solid state relay / similar to control the demister ? Can I get a 230v thermistor to save going low voltage DC control and the associated electronics etc as this needs to be left behind for the customer and not rocket science to repair / maintain ? Thanks in advance. Link to comment Share on other sites More sharing options...
Temp Posted July 6, 2017 Share Posted July 6, 2017 A thermistor is basically a resistor who's resistance varies with temperature. However the change in resistance is modest so you need a circuit that turns it into an on/off signal. This is usually done by a comparator that compares the resistance of the thermistor with that of an adjustable resistor. When one is greater/lower than the other it switches the output on/off. There are probably circuits on the web or modules on eBay/napkin that will do this. Some Heatmiser room stats have an optional external sensor mode but they only cover a narrow temperature range as you don't usually want to set a room to say >30C. Link to comment Share on other sites More sharing options...
Temp Posted July 6, 2017 Share Posted July 6, 2017 Napkin = Maplin! 1 Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 (edited) Have a look here, maybe something. Nice to deal with too. (Great site btw): https://www.esr.co.uk/products/frame_control-temperature.htm The I-108 maybe though you would need to stick it in an enclosure. Edited July 7, 2017 by Onoff Link to comment Share on other sites More sharing options...
dpmiller Posted July 7, 2017 Share Posted July 7, 2017 Cheap simple and accurate try something like Ebay item 1688573745, I use one to control a circ fan on top of a rad and it's been seamless for a couple of years. Pay a few quid more for a UK vendor if you're in a rush 112079287480. 1 Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 Thanks all. . 5 hours ago, dpmiller said: Cheap simple and accurate try something like Ebay item 1688573745, I use one to control a circ fan on top of a rad and it's been seamless for a couple of years. Pay a few quid more for a UK vendor if you're in a rush 112079287480. For the price, you can't go wrong. Its a bit over complicated for what I need but if it's only set it up once and forget then happy days. Questions... @Onoff. The one you linked is the most simple and 'fit for purpose', just 3 times the price of the one @dpmiller linked. Does anyone know how these two items will respond to a power cut? My fear is the cheaper eBay one may need buttons pressing for it to go back into temp sensing 'mode' which will be a right pita. Anyone able to confirm / deny with either unit please? This will be in an enclosure in kick space in the walk in wardrobe, so not something I want the customer to have to do anything with ( ideally ). Cheers. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 Oh, as I need to mount the thermistor like yesterday, can anyone tell me the specifics of the supplied thermistor so I can go grab one now from Napkin ( @Temp PMSL lol. ) aka Maplin ? Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 (edited) Ive emailed Cebek's tech department to ask what happens in a power cut with the I-108 module. I'd suspect it carries on as before as the potentiometer sets the threshhold. The I-108 comes c/w probe: i-108.pdf Edited July 7, 2017 by Onoff Link to comment Share on other sites More sharing options...
dpmiller Posted July 7, 2017 Share Posted July 7, 2017 (edited) the wee one from Ebay doesn't care- temperature is hard set using dip switches. edit- crap! just realised I'd posted the wrong item, I'd composed a post offfering the digital one as well and deleted the wrong list sorry. try this: http://www.ebay.co.uk/itm/DC-12V-Heat-Cool-Temp-Thermostat-Temperature-Control-Switch-Thermometer-20-90-C-/282297684188?epid=1131968094&hash=item41ba40d0dc:g:RkcAAOSwDN1UPOpM Edited July 7, 2017 by dpmiller Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 4 minutes ago, dpmiller said: the wee one from Ebay doesn't care- temperature is hard set using dip switches. Needs a 12V supply though? The Cebec one is 230V. Link to comment Share on other sites More sharing options...
dpmiller Posted July 7, 2017 Share Posted July 7, 2017 good point. I was thinking of LV as Nick mentioned using an SSR. Link to comment Share on other sites More sharing options...
Temp Posted July 7, 2017 Share Posted July 7, 2017 (edited) Had a look at the I-108 data and is says it needs a 10KOhm NTC thermistor. Think that's same as Heatmiser stats. Annoyingly Maplin don't seem to stock them (strange). Rapid have Probes.. https://www.rapidonline.com/atc-semitec-103at-11-ip67-10k-precision-ntc-thermistor-probe-with-600mm-lead-61-2040 https://www.rapidonline.com/atc-semitec-103at-11-50081-ip67-10k-ntc-thermistor-probe-with-1500mm-lead-61-2041 Bare thermistors.. https://www.rapidonline.com/tks-dht0a103f34d3sy-10k-3435k-1-axial-glass-ntc-thermistor-55-1229 https://www.rapidonline.com/tks-ttc05103jsy-10k-5-radial-straight-lead-ntc-thermistor-55-1259 Film.. https://www.rapidonline.com/tks-ttf3a103f34d3ay-10k-1-insulation-film-type-ntc-thermistor-55-1265 Think any would probably work just a case of ease of mounting and response time. Edited July 7, 2017 by Temp Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 Really helpful. Cheers. So the film one, given its a 22mm SPEEDFIT pipe, could be literally wound on with a gallon of pvc tape. ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 What about the thermistor that's in with my multimeter for the temp range? Can I nick that and use it just to save any delays? If I can that would be the jam in my jelly roll . Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 (edited) There's an RS Components in Pontypridd. Should have a selection of 10K thermistors: https://uk.rs-online.com/mobile/search.html?searchTerm=Thermistor+10k Stick your multimeter probes across the thermistor to measure it's resistance. Where are you working/easy to get to? Swansea is it? Edited July 7, 2017 by Onoff Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 Boiler thermistor if really stuck? 1 Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 (edited) Would decent pvc tape last to attach it? As in would it go brittle? Edited July 7, 2017 by Onoff Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 48 minutes ago, Onoff said: There's an RS Components in Pontypridd. Should have a selection of 10K thermistors: https://uk.rs-online.com/mobile/search.html?searchTerm=Thermistor+10k Stick your multimeter probes across the thermistor to measure it's resistance. Where are you working/easy to get to? Swansea is it? Yes, Swansea. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 41 minutes ago, Onoff said: Would decent pvc tape last to attach it? As in would it go brittle? Maybe, yes. Just a thought. Maybe better to bond it for heatvteansfer, and use the pvc tape to hold it until the bond has cured ? How's that 12 ohms ( taken @18oC ambient ). I'd really like to just whack that in right now as it's stopping me plasterboarding. ? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 44 minutes ago, Onoff said: Boiler thermistor if really stuck? Cant see the woods for the trees sometimes. Cracking idea as they're off the shelf at P.Ctr. ? Link to comment Share on other sites More sharing options...
Onoff Posted July 7, 2017 Share Posted July 7, 2017 (edited) 21 minutes ago, Nickfromwales said: Yes, Swansea. I that ohms or k.ohms? If a 10K one there, in a room slightly below ambient you'd get a higher value. A cleverer person will be along shortly! EDIT: Ohms I think from zooming in? EDIT 2: I'm an IDIOT, just read you said it's ohms! So that's pretty low, does it make it a PTC thermistor? If so, no good as you want NTC, Edited July 7, 2017 by Onoff Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 7, 2017 Author Share Posted July 7, 2017 Maplin have a 15kohm one ( cpc one in stock ). Link to comment Share on other sites More sharing options...
Temp Posted July 7, 2017 Share Posted July 7, 2017 (edited) Just back from searching a wheat field in 27 degree heat for the Samsung one of my kids dropped on a sponsored walk so just a bit knackered but... 3 hours ago, Nickfromwales said: What about the thermistor that's in with my multimeter for the temp range? Can I nick that and use it just to save any delays? If I can that would be the jam in my jelly roll . Not sure what that is. Perhaps a thermocouple rather than a thermistor? Differently beasts. If you are going to use the I-108 it needs to be 10k not 15k or the temperature settings will be around 20C out. It might be possible to change a resistor or two on the I-108 to correct for this but the data sheet doesn't have a circuit diagram. Edited July 7, 2017 by Temp Link to comment Share on other sites More sharing options...
Temp Posted July 7, 2017 Share Posted July 7, 2017 3 hours ago, dpmiller said: try this: http://www.ebay.co.uk/itm/DC-12V-Heat-Cool-Temp-Thermostat-Temperature-Control-Switch-Thermometer-20-90-C-/282297684188?epid=1131968094&hash=item41ba40d0dc:g:RkcAAOSwDN1UPOpM Just for info that also uses a 10k thermistor. Link to comment Share on other sites More sharing options...
dpmiller Posted July 7, 2017 Share Posted July 7, 2017 that's a K-type thermocouple in the piccy. 1 Link to comment Share on other sites More sharing options...
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