Now that my new CH and DHW supplies are all complete I would like to monitor various temperatures from one place in the home without going into the plant room and looking at several dials, just convenience I guess. Getting the probes to insert under insulation etc., doesn't seem to be too much of a problem. The difficulty is getting a simple, cheap, monitor device that I can either scroll through or display up to 5 or 6 temperatures simultaneously, preferably mains powered. There are plenty of industrial gizmos available at £300 plus but many of them have other command functions that I'm not interested in. it's just simple monitoring I need, also I don't want a computerised system. Any ideas??

It'd be dead easy to build, but it seems difficult to find a ready to go unit.

The little four channel data logger I built last week (the Mk 2 in a continuing series of datalogger developments......) displays the temperature from four sensors whilst it's logging data to memory for download to a PC. It would be really simple to build one that just displayed temperature from multiple sensors, all that might be needed might be a bigger display or a scroll capability (easy to do). It looks like this with no sensors plugged in (excuse the rubbish photo, I just took it to show what it looks like):

Posted By: JSHarrisIt'd be dead easy to build, but it seems difficult to find a ready to go unit.

Could I manage it?

I've just roughly costed up the bits. The ucontroller is around £2.50, the display is around £20 or thereabouts (depends whether you can make do with 16 characters x 2 lines, or need maybe 20 characters x 4 lines) and the sundry components are maybe another £2 or £3 . If you want the sensors to plug in, then budget on around an extra £3 per sensor for connectors (my Mk 1 has the sensors hardwired). The power supply can be any low voltage adapter you may have lying around (mine's running on an old Netgear router wall wart). If you want it in a box than add another £5 or so for a plastic one from Maplin. The temp sensors are DS18B20 pre-calibrated three pin jobbies, that cost around £1 each if bought in quantities of 10 or more via eBay, or maybe £2.50 to £3.00 each if bought one-off from UK suppliers. Sensor cables can be just cheap telephone cable if they are going to be permanently wired up, or use thin three core flex if you want to make them OK for portable use. The sensors can easily be protected by some heatshrink sleeve, this will seal them well enough to cope with immersion if an adhesive lined sleeve is used. There may be another £4 or £5 worth of odds and ends.

Construction needs a bit of soldering, nothing too onerous. The main snag is that the ucontroller needs programming. No big deal, but it does need a special cable that costs around £12, plus a connector at around £1.50. I could probably programme up the odd chip or two for people, and might be able to put together some kits of electronic parts, but I probably don't have the time to make more than a few.

A 20 x 4 display is around £24, compared with the 16 x 2 display at about £12. Each temp display needs 7 characters if it's in the format "T1=+18*" where * is a space between readings. 20 x 4 would allow a display that showed three sensor readings per row (no need for a space on the final sensor display), or 12 sensors readings in total, although the ucontroller I have in mind would only read 7 sensors I think. It should be possible to have slightly more verbose displays with a bit of tweaking. Each temperature displayed needs three characters, a sign plus two digits.

The display doesn't need much soldering, just a handful of components on 0.1" pitch. The same goes for the rest of the components. Some thought needs to be given to the way the sensor leads are arranged. My Mk1 datalogger (just three channels, no display, the one that produced the last dataset on the other thread, see photo below) has the sensor leads permanently fitted, which is a pain when you have one of the sensors going through the wall to measure the OAT.

Sure, I can probably sort out a full list over the next day or so, with suppliers etc, or could maybe sort out a group buy type thing and maybe put together some PCBs to make it easier to build. It could be built on a bit of breadboard, but it's not hard to make a PCB (I use a laser printer, some photo paper, a domestic iron, a bit of copper covered board and some etchant - takes around 30 or 40 minutes per board).

I've used standard 3.5mm stereo jack plugs and sockets for the sensors. These are cheap and easy to hook up to thin cables and the sockets can be simply fitted into drilled holes in a case. The sensor on the end of the cable is only about 7 or 8mm in diameter with the heat shrink over it (could maybe be made a mm smaller with something like a blob of araldite over the wires instead of the heats hrink). The 3.5mm plugs are around 9 or 10mm diameter.

Making a datalogger is a fair bit more work than just a simple multi sensor temperature display, as it needs a real time clock, some memory to store the data and a means of setting it up (setting date, time, sample rate etc). I'm working on making one that is stand alone, that doesn't need to be hooked up to a PC to be programmed and dump data. I was trying to get a USB interface working, but have found a cheap way of talking to a uSD card, so am working on using that instead. The idea is that the settings will just be a text file, loaded on to the uSD card via a PC and card reader (or any other device that will write a text file to one of these cards). The stored data will be on another text file on the card, in comma separated value format that can be read straight in to a spreadsheet.

Can you count me in too please JSH. I have to admit to never doing any electronic stuff before, just some domestic wiring, so all the talk of breadboards, etchant, RJ11, plugs etc., is all a bit double Dutch. I'm a cabinet maker by trade so it will probably all end up in very smart Masur Birch housing, or something like.
I dont know if my needs are the same os STs, but ideally, I'm after about 6 sensors, ( I could come down to 4 if that makes a difference). The sensors are all to be inserted into either cylinder pockets or inserted under insulation, so no water contact, I may consider an outside sensor though. Ideally, they all need to be wired into a nearby wiring centre, and from there on to the house utility cupboard kitchen via a single multicore cable.

Mike

I'd be interested as well - simple display for 3 or 4 sensors would be okay, although a data logger also sounds of interest. Sensors would be inserted in pockets, with minimum of 1.5m long leads.
Gary

Did anything come of these plans. I am now looking to link 5 sensors together and would be very interested to know where this project went.

There's someone on ebay, in Hong Kong selling digital temp readout devices complete with 2 wired probes. Have a look at item number 280798781199 at £12.90 and free p&p, do you think they might be worth a punt? Only trouble seems to be if you have two or three of these can you buy a housing for them and can the probes be lengthened. I asked the question to the seller but no reply.

There is also a probe DS18B20 with real thick wires attached which even I could attach to something. I am a bit like JSH though and am too busy building the house at present to teach myself information systems again. So thanks owlman; I am going to invest in the HK readout device and will report back in due course.

SparkFun have just introduced these pre-wired and sealed 1-wire temperature sensors:

http://www.sparkfun.com/products/11050

Nothing magic about them but might be convenient for somebody who just wants to stick a bunch of sensors in place then think about how to use them later.

I like SparkFun and have bought and used a fair bit of their stuff (the uSD card interface I'm using in the logger is one of theirs). They do often just market stuff that they buy in direct from China, though, so the chances are that both are of similar quality.

having now sealed half a dozen or so DS18B20s on to cables as remote sensors I think I'd rather just buy the ready made ones, as the premium over the £1 or so per sensor I've been paying for bare sensors seems reasonable to me.

Posted By: JSHarris...............I've taken a punt and ordered a handful of the really cheap ones I linked to as an experiment (5 off displays and sensors came to just over £8 inc free postage!).

How are you powering them JS? The listing doesn't seem to say. Do you intend lengthening the cable.

Took delivery of a temperature reading device from Hong Kong yesterday and it works (after a little experimentation due to poor instructions). The device is Item title:Digital Temperature Panel Meter Monitor Thermometer °C- Item ID:280565422469 - Price: £12.90.

It comes with 2 probes which are 0.5 degrees out with each other but once you make an allowance for that it seems to work alright.