Post by thread:[OT]: Temperature Switch

Hello everyone.. I am looking for something surprisingly hard to find: a temperature switch operating in the 3 deg C range. i.e. a straight on/off thermostat that need not be adjustable (but could be). The load being switched draws 1 mA or so at 220 V (a relay coil). Has someone seen what I'm looking for? Thanks Roland -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

On Tue, 18 Jul 2000, Roland Andrag wrote: > I am looking for something surprisingly hard to find: a temperature switch > operating in the 3 deg C range. i.e. a straight on/off thermostat that need > not be adjustable (but could be). The load being switched draws 1 mA or so > at 220 V (a relay coil). Has someone seen what I'm looking for? Dallas DS1620 programmable thermometer/thermostat and a suitable relay driver will do this. Dale --- The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" (I found it!) but "That's funny ..." -- Isaac Asimov -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> From: "Roland Andrag" <spam_OUTrandragTakeThisOuTICON.CO.ZA> > Hello everyone.. > I am looking for something surprisingly hard to find: a temperature switch > operating in the 3 deg C range. i.e. a straight on/off thermostat that need > not be adjustable (but could be). The load being switched draws 1 mA or so > at 220 V (a relay coil). Has someone seen what I'm looking for? Yes, there's one in my fridge, but you can't have that. :> Seriously, a supplier of spares for refrigerators would be a good place to start. Or a scrapyard/recycling centre if you only need one. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

I am currently building just such a beast! It turns off at 90F, and turns back on at 85F. This is a simple Schmitt trigger implemented using a LM2904 op. amp with a thermistor sensor. The supply is 12VDC. The output is a SPST relay with 10A contacts. They cost me about $20US to make, but I am considering volume production (10,000+). There's even a green LED to indicate operation. Temperature range is adjusted by changing fixed resistor values. The Dallas units are great too as the thermo-sensor is already built in. The range and setpoints are digitally adjustable, and there is an open collector output. The only issue I have with it is the package is too big to remote mount, let alone the PCB you install it on. Craig > {Original Message removed}

> I am looking for something surprisingly hard to find: a temperature switch > operating in the 3 deg C range. i.e. a straight on/off thermostat that need > not be adjustable (but could be). The load being switched draws 1 mA or so > at 220 V (a relay coil). Has someone seen what I'm looking for? Two chip solution: an LM75 or DS1620 + a 12c508 to set the switch point? -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

On Tue, 18 Jul 2000, w. v. ooijen / f. hanneman wrote: > > Two chip solution: an LM75 or DS1620 + a 12c508 to set the switch point? You don't need the PIC for that. Once set, the DS1620 will retain its settings. You could have a 1620 setup box (PIC based, of course!! ;-) to program the thermostats before insertion. I've got a DS1620 .H file, if anyone needs C code for it... Dale --- The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" (I found it!) but "That's funny ..." -- Isaac Asimov -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 03:48 PM 7/18/00 +0200, you wrote: >Hello everyone.. > >I am looking for something surprisingly hard to find: a temperature switch >operating in the 3 deg C range. i.e. a straight on/off thermostat that need >not be adjustable (but could be). The load being switched draws 1 mA or so >at 220 V (a relay coil). Has someone seen what I'm looking for? Sounds like you just need a thermostat. There is a type that looks a bit like a TO-3 transistor case, but with a couple of spade (Faston) connectors on the 'bottom'. They are surprisingly accurate and cheap (at least in large quantities, cheaper than semiconductor solutions by far since they include both a sensor and a power switching device and require no power supply). The main limitation is that the differential (hysteresis) between on and off temperatures has to be fairly large (several degrees C, IIRC). Try an appropriate directory for your location, these are more appliance parts than electronics items. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam@spam@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>3 deg range, 220V 1mA If by 3 deg range you mean 0..3 deg C then look for a 'garage thermostat'. These are made to turn on the heating in the garage in cold countries, when temperature drops to the frost point, to avoid obvious problems and wall cracking by ice. Also sensors for automotive use exist (even in kit) for frost warning (icing). They have relay outputs. If by 3 deg. range you mean just 3 deg hysterezis in the 0..100 deg C range then you want an industrial rail mount thermostat with 2% precision class. This will usually switch 10 or 16A directly so you need no relay. If you want to build one, then pick a sensor (chip or thermistor) and build it. And last, if you have to turn on heating to avoid freezing, and have no other resources, then use a fridge thermostat as is (not the deep freeze kind). This will switch 8A inductive usually, and is EXTREMELY reliable. MUCH more so than all the others combined probably. Also very cheap (~$10 in ones). And this is off topic as it has no PICs. Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

How much is it and what are the specs? Craig {Quote hidden}> -----Original Message----- > From: pic microcontroller discussion list > [PICLISTKILLspamMITVMA.MIT.EDU]On Behalf Of Roland Andrag > Sent: Monday, July 24, 2000 3:20 AM > To: .....PICLISTKILLspam.....MITVMA.MIT.EDU > Subject: Re: [OT]: Temperature Switch > > > Thanks for all the replies! I have found and will be using a thermostat > normally used in fridges. > > Thanks again! > Roland > ----- Original Message ----- > From: Dale Botkin <EraseMEdalespam_OUTTakeThisOuTBOTKIN.ORG> > To: <PICLISTspam_OUTMITVMA.MIT.EDU> > Sent: Tuesday, July 18, 2000 4:09 PM > Subject: Re: [OT]: Temperature Switch > > > > On Tue, 18 Jul 2000, Roland Andrag wrote: > > > > > I am looking for something surprisingly hard to find: a temperature > switch > > > operating in the 3 deg C range. i.e. a straight on/off thermostat that > need > > > not be adjustable (but could be). The load being switched > draws 1 mA or > so > > > at 220 V (a relay coil). Has someone seen what I'm looking for? > > > > Dallas DS1620 programmable thermometer/thermostat and a suitable relay > > driver will do this. > > > > Dale > > --- > > The most exciting phrase to hear in science, the one that heralds new > > discoveries, is not "Eureka!" (I found it!) but "That's funny ..." > > -- Isaac Asimov > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > -- > http://www.piclist.com hint: To leave the PICList > @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu > -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu>