# making your own thermostat



## skimpy

I saw this on a forum last year and ive been trying to find it.

Anyone else seen it....how to build your own thermostat? Got an electronics engineer fiance who is able to build one, but it is very bulk, was looking to offer him the article.


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## Magpye

This probably doesn't help, but:

Thermostat Kit

attached to:

Temperature Module

Thermostat for under 20.00


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## skimpy

Magpye you are a star. Paul wants to buy them now instead of make them. Cheers for that.

It was an american forum i was on in 2005 that i saw this D.I.Y. guide to building your own thermostat, but at that price, why bother!! mheers again dude!


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## Magpye

Yeah, stunning idea; don't know why I didn't think of it either. Like mindless fools we always look for the easy option and buy stuff that is premade. Assembling a DIY kit is significantly cheaper - however consideration should be given to reliability and what happens when the circuit fails - is there a cut-out system. If not, and your fiance can "add" one, please encourage him to post the plans and components!

Regards

Dave


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## skimpy

Magpye said:


> Yeah, stunning idea; don't know why I didn't think of it either. Like mindless fools we always look for the easy option and buy stuff that is premade. Assembling a DIY kit is significantly cheaper - however consideration should be given to reliability and what happens when the circuit fails - is there a cut-out system. If not, and your fiance can "add" one, please encourage him to post the plans and components!
> 
> Regards
> 
> Dave


he is on the case. It would be a case of him constructing the circuit boards from scratch, or obtaining the circuit diagrams for the boards. but he thinks it is quite straightforward to incorporate something into it, with perhaps a simple buzzer or LED to alert you to a failure.

I have been on at him for ages to put his mind to this, and you have helped him get motiates. Will update this thread...


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## skimpy

sp/ motivated!! stupid cookies wont let me edit post


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## mEOw

i actually ripped our new pulse stat apart when we got it to see how it worked.. 
Basically it is a pic microprocessor inside..
There is a 5V power source for this (VERY simple power supply i might add.. could be iproved LOTS which would improve reliability if thats a problem)
And a switching circuit...

There is a variable resistor conencted up as a voltage divider which is passed into an on chip ADC, the pic will then use this signal and a lookup table to work out what the desred temperature is..
Similar with the temp probe.. it goes into an on chip ADC and again will be compared to a lookup table which will work out actual temperature..
The chip then comapres these values and adgusts the pulse length apropriatly useing PWM (which again is built into the chip on this particular pic microprocessor)

All in all there is about £3 worth of components inside.. I have a few designs i made before we bought this thermostat, 2 of which have a usb port so you can connect to a pc to remotley monitor the temps, log the temps, etc.. 
I will eventually get myself into gear and start offering my thermostats which have usb as a finished product but at the moment i havent even built a prototype hence why i had to go out and buy one. Was just happy to see that the comercially available models were useing basically the same setup as i would, just not quite as well built as mine would be (mainly talking about the power supply for the pic here)..
I should mention i studied electronics engineering to HND level and design/ build my own amplifiers and othe rodds n ends as a hoby so this is all just a bit of fun for me..
Owen


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## mEOw

also i should add that i am very unhapy with the thermostat we bought, simply because there is NO failsafe if the chip goes down.. the heater will either latch off or more probably looking at the circuit latch on.. Which when you look at how they supply power to the chip is actually pretty worrying... but then i worry about a lot of things..lol


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## skimpy

mEOw said:


> i actually ripped our new pulse stat apart when we got it to see how it worked..
> Basically it is a pic microprocessor inside..
> There is a 5V power source for this (VERY simple power supply i might add.. could be iproved LOTS which would improve reliability if thats a problem)
> And a switching circuit...
> 
> There is a variable resistor conencted up as a voltage divider which is passed into an on chip ADC, the pic will then use this signal and a lookup table to work out what the desred temperature is..
> Similar with the temp probe.. it goes into an on chip ADC and again will be compared to a lookup table which will work out actual temperature..
> The chip then comapres these values and adgusts the pulse length apropriatly useing PWM (which again is built into the chip on this particular pic microprocessor)
> 
> All in all there is about £3 worth of components inside.. I have a few designs i made before we bought this thermostat, 2 of which have a usb port so you can connect to a pc to remotley monitor the temps, log the temps, etc..
> I will eventually get myself into gear and start offering my thermostats which have usb as a finished product but at the moment i havent even built a prototype hence why i had to go out and buy one. Was just happy to see that the comercially available models were useing basically the same setup as i would, just not quite as well built as mine would be (mainly talking about the power supply for the pic here)..
> I should mention i studied electronics engineering to HND level and design/ build my own amplifiers and othe rodds n ends as a hoby so this is all just a bit of fun for me..
> Owen


 
cheers for this. paul is just finishing up his Bsc. he works in an industrial plant, and came home with industrial sized pats robbed form the workplace, each component worth £200 upwards, and far too bulky for home use. I will be badgering him to pursue this further once he has his exams out of the way, as he is always making something or other, usually for his own benefit.. it's my turn now to get something useful!!


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## skimpy

just to add, isn't it criminal the prices they charge for premade thermostats, when in reality, the components cost next to nowt, so long as they aren't industrial!!


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## mEOw

feel free to let him pm me or add me to msn or something when he isnt busy, we can talk it through in more detail.. dont really want to go into huge amounts of details on the forum because i will just blind people with technical jargon they wouldnt understand anyway and as i say i havent even built prototypes for mine yet but i have no doubts about whether they would work or not now seeing as the comercially available one i ripped apart was basically identicall to my designs just built on the cheap and with a heftyer price tag than what id be looking at producing them for.. 
I actually have a design here for a pulse stat that can controll 2 seperate heaters independantly (even in two seperate vivs) and has an lcd display that displays desired and actuall temps of both at the same time, also has usb port so could be linked to a pc for datalogging and remote monitoring n stuff, im just no good at the pc softaware side of things but i know a few people that can do that for me..  
Owen


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## mEOw

and yes.. as i said.. it would cost me about £3 in components to reproduce the one i ripped apart, Fair enough i would have to write the code for the microprocessor myself BUT there is no code there that isnt readily available on the net (even in the application notes!!)
If i could build it so cheaply imagine how cheap it is for these big companies to build! 
Owen


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## reptiles-ink

dont forget though that in order to sell them they have to get CE approved.
EMC and LVD testing would be required for CE testing. Budget price is £1,850.00.


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## mEOw

yup.. if i were to sell them as a finished product.. but i dont really plan on selling them, and if i did i would probably only sell the pcb and programmed chip and possibly a pack with the other components needed, and only through the forums  
Owen


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## reptiles-ink

yeah thats fair enough just that I would help avoid legal problems if you were to be selling them as I am going down the same path at the moment.


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## mEOw

Yeh, i know all about the testing that would need doing..  
BUT.. if i were to sell fully asembled ready to go units then because i live in wales i could get a grant that would pretty much cover all the startup costs.. But again i dont really plan on going down that route, too much like hard work, i just plan on building my own and publishing my plans on the net and offering pre programmed chips and PCB's.. That way the DIY minded people could have a little project... 
Thanks for making that clear though, Will put other people off trying to use my designs for omercial products..lol 
Owen


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## reptiles-ink

yeah very true, but then you could use a chip that encrypts the data so they cant read it anyway.
I have looked into using displays etc to show the temps but for now I am just doing conventional pulse and dimmer, the more elaborate ones can come later


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## mEOw

the thing is.. adding the display isnt any more work.. and yes, i can burn the chips and set a flag that stops it being easy to "pull" the code back off the chip..


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## Dizaster66

*tap tap tap*

Tap tap tap , 

Come on mEOw are those kits available yet 

Its been more that 12 hours 

LoL

Seriously if you do decide to make a kit 
I'd be up for one or 2 or 3 or ......
howmany snakes can I sneak past the wife 

hee hee

Dizzy


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## skimpy

Hey Owen, thanks for the offer. Imay encourage Paul on for a look later this evening. He doesn't do msn, but Im sure he will be in touch somehow. goodluck to you, I heard him on the phone to some components company last week,and the conversation turned into more than an hour! Talk the hind legs off a donkey and then some!!

WE wouldn't be interested in selling either as finished products, but what are the legalities surrounding selling DIY kits? 

Perhaps I am underestimating the work involved in construction, but im still thinking backto the thread I saw last year about making your own,and it seemed straightforward enough...


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## mEOw

well.. i have just found something very interesting... A chip that basically has an on/off thermostat all on one chip, all that would be needed to make an on/off thermostat useing it would be a power supply and a switching circuit.. 

My thoughts are it would be very good for people with large stacks as you could build one box that has all the switching circuits in it and a power supply.. plug in as many "sensors" as you need and basically control as many heaters as you want... 
Only downside to it is that you would need to program it from a PC.. (to set the on and off temperatures)
At the moment i have put on hold my other projects to concentrate on this, just waiting for my sample chips to arrive now  wouldnt be any cheaper but COULD be as small as you like.. i mean peronally i would build the lot into a power strip and just have the sensors plug into it.. 

I dont see any problems with offering kits, we do it on other forums i am member of all the time.. but most of them are electronics orientated so my worries would be people messing up building the thermostats, for this reason i would have to make them pretty fool proof..lol 


Owen


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## skimpy

mEOw said:


> well.. i have just found something very interesting... A chip that basically has an on/off thermostat all on one chip, all that would be needed to make an on/off thermostat useing it would be a power supply and a switching circuit..
> 
> My thoughts are it would be very good for people with large stacks as you could build one box that has all the switching circuits in it and a power supply.. plug in as many "sensors" as you need and basically control as many heaters as you want...
> Only downside to it is that you would need to program it from a PC.. (to set the on and off temperatures)
> At the moment i have put on hold my other projects to concentrate on this, just waiting for my sample chips to arrive now  wouldnt be any cheaper but COULD be as small as you like.. i mean peronally i would build the lot into a power strip and just have the sensors plug into it..
> 
> I dont see any problems with offering kits, we do it on other forums i am member of all the time.. but most of them are electronics orientated so my worries would be people messing up building the thermostats, for this reason i would have to make them pretty fool proof..lol
> 
> 
> Owen


 
Hey. im glad you are pursuing this. It's a grand idea. Paul and i split up so he wont be doing this anymore. remember me if you ever do get this off the ground : victory:


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## mEOw

sorry to hear that hun, I'll keep you posted about my progress
Owen


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## skimpy

mEOw said:


> sorry to hear that hun, I'll keep you posted about my progress
> Owen


 
Cheers, im interested, and this foum is keeping me going just now. without going into detail, we were gonna get married next year, and im pretty gutted


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## reptiles-ink

by the sounds of it I am familiar with the chip.
It can be ran via a pc for thermostat/thermometer use but can also be programmed with defined setpoints to be used as a stand alone thermostat.
I believe the sensor used in conjunction with the chip is a 3 pin device a bit bulkier than a thermistor but still useable.


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## mEOw

nope, in that case you arent familiar with the chip im talking about  
Probably from the same family though, The one im talking about has the sensor on chip and is an 8pin device.. Acording to the datasheet it is acurate enough and has fast enough response times to be usefull.. We will have to wait and see when my samples arrive though, could be a good base for a very cheap mat stat or on/off thermostat though. Been offered a load of these chips as "surplus" for under £1 a piece.. 
and yes, it uses a 3 wire bus so it can be connected to pretty much anything you want or used stand alone, the way i plan on useing it is stand alone and just useing the pc to program the chips set points..... 
Owen


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## reptiles-ink

yes I have seen the ones with built in sensor. the drawback is you will need the chip inside the viv for it to work.
you will find the 1 I mentioned at a similar price and it couples to an external sensor.


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## mEOw

aye, the drawback is that the chip would need to be inside the viv, the one you mentioned would probably be better. 
but i was planning on putting all the electronics into a power strip and just haveing the thermostat "probes" plug in so haveing the chip in the viv isnt such a problem really as long as it is sealed properly.. also i have been offered these chips for under £1 a piece which is why i want to try and use them.. It might not work though.. all i can say is an 8 pin smd chip with some interferance suppressing circuitry will happily fit isnde a probe similar size to the ones on a habistat thermostat..lol 
Owen


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## Dizaster66

Did anything come of this project ??

I was looking at the maplin stat kit , noticed it was only 24v rated.
Is it just an easy job to drive another mains rated relay from this smaller one ??


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## skimpy

yeah i'd be interested to know how it's going too. Good news, me and Paul got back together, so i will bend his ear again soon. just gotta let him get his final exams out the road


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## mEOw

Hey guy's, I have been playing around with a few ideas, nothing solid built yet, emily is away at her parents and delivering / collecting rep's for us and other people so as soon as she is back and i can get a break from doing all the housework and looking after all the rep's i'll order the rest of the components i need and prototype some ideas  I would post schematicsbut they arent really any good unless i post code for the chips, etc aswell and i havent finished writing / tested any of my code yet so that will have to wait..lol

And yes, The maplin kit would drive another relay easily.. there are other kits out there aswell, there is a 12V on/ off kit on ebay cheap that is designed for incubators, could easily use it to drive a relay that switched a mains device (heat mat, etc) on and off..  
Owen


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## Dizaster66

I was tinkering on the tinternet today and came across this.

1048 - Electronic Thermostat

Its a thermostat kit, which switches mains voltage. (240v at 1A)

£8 for kit
then need PSU 12v £ ??
Cable plugs and sockers £5

Will it be any cheaper than buying a readymade thermostat ?


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## ackie123

well this seems dead in the water, but i dont see why people just hook up a simple dimmer switch to the light in the viv, and play around till you get the right temps via a thermometer in the tank, i done this for about £12, and works a charm.


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## Stuart C

but then what happens if theres a rise in temperature in the room, or a cold snap like reciently, or the vents get blocked and heat builds up, theres no automatic way to adjust a manual dimmer to compensate, although I do see where your comming from.

Did anything ever come from this? I for one would be interested in building these!


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## fixitsan

Stuart C said:


> but then what happens if theres a rise in temperature in the room, or a cold snap like reciently, or the vents get blocked and heat builds up, theres no automatic way to adjust a manual dimmer to compensate, although I do see where your comming from.
> 
> Did anything ever come from this? I for one would be interested in building these!


In theory, it ought to be simple to include a thermistor into the dimmer control, potentiometer ciruit, to produce the required signal differential required to make the dimmer respond to temperature changes.

The problem is that only a few people will feel confident enough to take a soldering iron to a mains dimmer and manage not to make the circuit dangerous (IE use proper isolation techniques and sleeving), and the rest will just buy something else to be on the safe side, laying off the extra few pounds it costs against perceived ultimate safety.

Chris


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## ackie123

or you could check the thermometer in the viv a few times a day, besides, if your house is that poorly insulated you shouldnt be keeping reptiles.


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## bman

Couldn't you use the alarm output on one of the cheap maplin in/out thermometers at energise a cutoff timed relay. say five minutes.
mainly for emergency use. as someone suggested earlier use a dimmer for the bulk of temp regulation.
The maplin kit is a switching one not a dimming so you'd have a bulb flashing on and off to regulate the temperature....


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## fixitsan

ackie123 said:


> or you could check the thermometer in the viv a few times a day, besides, if your house is that poorly insulated you shouldnt be keeping reptiles.



You're talking about manual temperature control versus automatically controlled temperature now. 

What would happen if you went to check the temperature and it had crept up 5 degrees too high because the sun has moved around and is now shining into the room and partly onto the viv....you're going to have to turn the dimmer down...then a few hours later the sun disappears and you're going to have to turn the dimmer back up again. Is it worth the bother ?

Say each check and adjustment, 4 times a day, takes 15 seconds, that's 1 minute per day. That's 365 minutes, or 6hrs and 5minutes in a year.

Let's say that you've saved yourself £15 by not going automatic and opting for manual, £15 divided by , say, 6 hours, means your time is worth £2.50 per hour.

Let's say the stat lasts 10 years now, and you spend 61 hours in that time checking and adjusting your temps. You only saved £15, and that's at today's prices....in ten year's time £15 is worth much less, and your time should be worth much more, but even by today's standard you're going to be paying yourself about 24p per hour. Take the cost of living into account and the fact that minimum wage in ten years time could be more than double what it is now, over £10 per hour then at least, why are you only valuing your time at pennies per hour ?!


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## reptiles-ink

fixitsan said:


> You're talking about manual temperature control versus automatically controlled temperature now.
> 
> What would happen if you went to check the temperature and it had crept up 5 degrees too high because the sun has moved around and is now shining into the room and partly onto the viv....you're going to have to turn the dimmer down...then a few hours later the sun disappears and you're going to have to turn the dimmer back up again. Is it worth the bother ?
> 
> Say each check and adjustment, 4 times a day, takes 15 seconds, that's 1 minute per day. That's 365 minutes, or 6hrs and 5minutes in a year.
> 
> Let's say that you've saved yourself £15 by not going automatic and opting for manual, £15 divided by , say, 6 hours, means your time is worth £2.50 per hour.
> 
> Let's say the stat lasts 10 years now, and you spend 61 hours in that time checking and adjusting your temps. You only saved £15, and that's at today's prices....in ten year's time £15 is worth much less, and your time should be worth much more, but even by today's standard you're going to be paying yourself about 24p per hour. Take the cost of living into account and the fact that minimum wage in ten years time could be more than double what it is now, over £10 per hour then at least, why are you only valuing your time at pennies per hour ?!


 

Plus what if you decide to go out for the day, a weekend or even on holliday? Will you get a neighbour to go round every few hours to check and adjust it?


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## iangreentree

I would love to but some of these kits if they can be done:notworthy:I'll be watching the thread :2thumb:


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## reptiles-ink

iangreentree said:


> I would love to but some of these kits if they can be done:notworthy:I'll be watching the thread :2thumb:


 If I can find where all the bits are after our house move I should be able to sort out some pulse stat kits.
The main thing is if you are able to solder, if not I could populate the circuit board.


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## mrhoyo

if the pulses are cheaper than a microclimate stat i would be very interested. ideally would just be screwing bith together etc though, soldering doesnt go well with my fingers. it bloody hurts!


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## reptiles-ink

mrhoyo said:


> if the pulses are cheaper than a microclimate stat i would be very interested. ideally would just be screwing bith together etc though, soldering doesnt go well with my fingers. it bloody hurts!


 I should be able to do them so it's just a matter of putting the board into a box and connecting the wires onto screw terminals and putting a mains plug on.


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## ackie123

fixitsan said:


> You're talking about manual temperature control versus automatically controlled temperature now.
> 
> What would happen if you went to check the temperature and it had crept up 5 degrees too high because the sun has moved around and is now shining into the room and partly onto the viv....you're going to have to turn the dimmer down...then a few hours later the sun disappears and you're going to have to turn the dimmer back up again. Is it worth the bother ?
> 
> Say each check and adjustment, 4 times a day, takes 15 seconds, that's 1 minute per day. That's 365 minutes, or 6hrs and 5minutes in a year.
> 
> Let's say that you've saved yourself £15 by not going automatic and opting for manual, £15 divided by , say, 6 hours, means your time is worth £2.50 per hour.
> 
> Let's say the stat lasts 10 years now, and you spend 61 hours in that time checking and adjusting your temps. You only saved £15, and that's at today's prices....in ten year's time £15 is worth much less, and your time should be worth much more, but even by today's standard you're going to be paying yourself about 24p per hour. Take the cost of living into account and the fact that minimum wage in ten years time could be more than double what it is now, over £10 per hour then at least, why are you only valuing your time at pennies per hour ?!



so you think 4 minutes a day is to much time to attend to your pets? and as with temperature drops of 5 degrees, do you think they have constant temps in the wild? they are resilient creatures they will deal with it, just not for prolonged periods of time, 
besides the saving of the money is only one factor such a simple device is less likely to break unlike the magic eye thermostat my missus bought for £45 last month, waste of money, it constantly thinks its night if the temp is set to high. But in all fairness if you don't like the idea don't use it.



reptiles-ink said:


> Plus what if you decide to go out for the day, a weekend or even on holliday? Will you get a neighbour to go round every few hours to check and adjust it?


do you let your pets starve then if you go on holiday then? twice a day is sufficient for night time temps and day temps to be regulated.


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## mrhoyo

reptiles-ink, i would be very interested indeed then. especially because my dimmer buzzes and it does my head in and because the cheapest i can get a pulse is about 25 quid.
dont really want to get into the automatic vs manual argument but why give reps inadequate temps and have to change them manually when you could have a much quicker acting system with more stable temps plus the fact you dont have to check temps, turn dial, check temps again, wait a bit, check temps, turn dial etc for about 30 quid?


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## reptiles-ink

ackie123 said:


> do you let your pets starve then if you go on holiday then? twice a day is sufficient for night time temps and day temps to be regulated.


 Just how would they starve? They get fed every 7 to 10 days plus there are several people who can feed, water, clean them etc. in my absence. 
F:censor:G T:censor:R


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## ScottyGurn

hi, could someone please explain to me what i have to do to make my own thermostat.

I clicked both the links and i am looking at both the things and thinkin how do they go together.

is that all i would need just the thermostat and the temp module? or anything else?

thanks

scott


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## reptiles-ink

skimpy said:


> cheers for this. paul is just finishing up his Bsc. he works in an industrial plant, and came home with industrial sized pats robbed form the workplace, each component worth £200 upwards, and far too bulky for home use. I will be badgering him to pursue this further once he has his exams out of the way, as he is always making something or other, usually for his own benefit.. it's my turn now to get something useful!!


 The stat in the link is a 12 volt stat.
You would need to get a 12v supply to run it and also connect to the mains after the relay output in order to run a mains operated heater.


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## fixitsan

.....


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## fixitsan

ackie123 said:


> so you think 4 minutes a day is to much time to attend to your pets? and as with temperature drops of 5 degrees, do you think they have constant temps in the wild? they are resilient creatures they will deal with it, just not for prolonged periods of time,
> besides the saving of the money is only one factor such a simple device is less likely to break unlike the magic eye thermostat my missus bought for £45 last month, waste of money, it constantly thinks its night if the temp is set to high. But in all fairness if you don't like the idea don't use it.


I don't quite understand what this has to do with how much time you spend with your pet. Unless you actually live _for_ your pet then anything you do to monitor and control the temperature in your absence is always going to improve the standard of care.

I use a variety of temperature controls. The rabbit hutch frost prevention system and the chameleon viv both use industrial PID controllers, but then I got them for free, although I norte there are some very cheap ones on ebay now, like item number 230328939079

In fact, if you do a widlcard search of ebay for " temp* contr* " there are plenty of alternatives for sale which are cheaper than buying a homemade kit, adding VAT, then adding the postage, then the fuel to go to Maplins and buy a plastic box, and grommets and terminals and.....


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## fixitsan

mrhoyo said:


> if the pulses are cheaper than a microclimate stat i would be very interested. ideally would just be screwing bith together etc though, soldering doesnt go well with my fingers. it bloody hurts!


If you just want something that needs wiring together, then this is good value, currently at £5 plus £5 postage. It can act as a pulse, as an off-on mat stat type of controller, it has softstart to prevent maximum output from being invoked straight away ( AHS heaters also do this) and can be tuned. AND all the documentation you need is available online.

Have a look at the datasheet in the ad, two nice digital displays inside a purpose built enclosure, *ERO TMS THERMAL CONTROLLER on eBay, also, Industrial Automation Control, Electrical Test Equipment, Business, Office Industrial (end time 05-Mar-09 18:08:57 GMT) 


*


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## mrhoyo

looks good and the price is nice but havent got a frigging clue how id set it up!


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## fixitsan

mrhoyo said:


> looks good and the price is nice but havent got a frigging clue how id set it up!


If you were looking at wiring together some prebuilt kit modules then the task is about the same complexity. You only need to connect 6 wires to 6 screw terminals.

I made an instructional document with photos of the last setup I made...you should be able to find it here..
Download PID Wiring.pdf from FileFactory.com

<a href="http://www.filefactory.com/file/af315ch/n/PID_Wiring_pdf">Download PID Wiring.pdf from FileFactory.com</a>

Chris


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## fixitsan

mrhoyo said:


> looks good and the price is nice but havent got a frigging clue how id set it up!



If the other link doesn't work, try this one.
PID Wiring.pdf


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## mrhoyo

so thats all it is, 6 wires? would it be as accurate as a prebuilt stat? electronics isnt my strong point, excuse my thickness


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## iangreentree

so the one on ebay what way do you connect it?? i couldn't up load wire diagrame ?
how would you connect sat a heat mat or ceramic heater to it?


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## fixitsan

iangreentree said:


> so the one on ebay what way do you connect it?? i couldn't up load wire diagrame ?
> how would you connect sat a heat mat or ceramic heater to it?


If you take a look at the wiring diagram I posted in a previous reply, you can see how I wired the device I used. Luckily the international standard of symbols works our way because the device on ebay and the device in my wiring diagram both have similar symbols drawn on the side of them.

The manufacturer's datasheet shows where the relay contacts are , designated as 'NO' an 'C'. The thermocouple + and - are self explanatory, you wire the thermocouple's positive to + and it's negative to - , and themains connection is well lavbelled with N and L.

you should refer to my wiring diagram and check how I completed the circuit by using a single wire link to bring the switching relay into the circuit.


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## fixitsan

mrhoyo said:


> so thats all it is, 6 wires? would it be as accurate as a prebuilt stat? electronics isnt my strong point, excuse my thickness


Accuracy would be definately as good as anything else you can buy. It will also respond better to changes from the steady state temperature, because it responds to the rate of change and not just the difference between the actual temperature and the target temperature.

A full PID control system is overkill for a vivarium, but yoiu can lose the 'I' term by setting it to zero and then you have a PD controller. You can also get rid of the 'D' term by setting that to zero, which leaves you with a P controller only, and P stands for proportional, as in Pulse proportional, so for comparison even in it's most basic setup it is a proportional stat.


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## mrhoyo

Thats brilliant. would i need to order anything else or is that it?


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## fixitsan

mrhoyo said:


> Thats brilliant. would i need to order anything else or is that it?


It will replace what you were going to do before with the kit idea, so you will still need the same parts, such as a mains plug and lead, and a mains socket for the heat mat would be a good idea too.

In my wiring explanation document you can see the thermocouple yoiu will need to buy ot get it working.

If the controller goes much over £15 you will not save anything, but i though that it was cheap and didn't get many views, plus it acted as an example oif the sort of thing I was talking about.

I am only trying to make the point that if you absolutely do not want to use Microclimates or Habistats, then there are still better otions than solder-together kits and poorly fitted cases. These industrial controllers do need a bit of protection around the screw terminals,and to mount them properly you need to make a frame (or use a plastic box) with a square cutout of the right size, but if you're in no rush and can wait to get a well priced unit off ebay they make viable alternatives. Another benefit is that sometimes they come in four-channel varieties, so you can run 4 viv's from one central controller which minimises wiring.


Generally speaking, if you are only making a one-off, b thte time yoiu add the cost of the mains socket, the mains plug, a couple of metres of mains cable, good grommets and a case, the cost of implimenting a kit is quite high. The only time such a kit would help you save some money would be if you were fitting it into exosting equipment which already had the necessary wiring inside.

But, I would be happy to be proved wrong too !

Chris


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## arthur cooke

I used to run my own company, closed in 2000 so's I could retire. Small companies can self certificate for all the required tests and CE mark.
cheers arthur.


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## fixitsan

arthur cooke said:


> I used to run my own company, closed in 2000 so's I could retire. Small companies can self certificate for all the required tests and CE mark.
> cheers arthur.



The thought had actually crossed my mind already about that.

Someone could buy PID controllers in bulk and fit them in an enclosure and sell it one as a multiple control unit ( I dont think there's any profit in single channel controls). But I wondered about the certification side of things. I've looked at the LV requirements and they seem straightforward enough.

Nevertheless, there's still a minimum price you would have to charge because the componnets aren't as cheap as some might want to believe


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## arthur cooke

If you use companies like RS,Farnels etc then components can be expensive. You have to search around, I used a guy who used to buy up bankrupt stocks of electronic components. Could get 4 resistors, carbon film for 1p. Out of it all now tho.
Anyway my point was that if you search I'm sure there are deals to be had. especially now.
cheers arthur.


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## mrhoyo

does that mean that someone could knock up cheap stats and sell them legally? sounds good to me!


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## reptiles-ink

mrhoyo said:


> does that mean that someone could knock up cheap stats and sell them legally? sounds good to me!


 self certification still costs initially so you would have to sell hell of a lot to get your money back.


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## mrhoyo

Ah. its not that good then. surely people could give them as home made gifts without certification? the people who receive them might wish to give a gift of money too?


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## iangreentree

did anything come of this thread?


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## mrhoyo

iangreentree said:


> did anything come of this thread?


apparently not:lol2:


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## fixitsan

mrhoyo said:


> apparently not:lol2:


'No clear winner' suggests to me that it isn't really worth buying a kit, and that the extra cost of all the hardware required to build it into a robust enclosure, and make it safe, makes it a better bet to buy something off the shelf where you at least get some sort of warranty


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## mrhoyo

If we could get mass produced stats at trade id be happy. Would be nice to make my own though, shame im an idiot when it comes to making things that actually work


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## Dextersdad

I've not thought of making one yet. May do now. I've repaired a couple in the past.


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## ShaneLuvsMonitors

I have used a standard dimmer switch as a thermostat to lower temps on a basking spot no automatic adjustment though so you have to fiddle with it a lot...


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## Jb1432

This sounds like a good idea shane, might have to try it. Will probs end up killing me by eleccy shock though.:lol2:


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## ShaneLuvsMonitors

Jb1432 said:


> This sounds like a good idea shane, might have to try it. Will probs end up killing me by eleccy shock though.:lol2:


 
Yeah its not to bad just make sure you know which wire goes where.... and £3.99 is cheaper than a dimming thermostat :lol2:


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## reptiles-ink

ShaneLuvsMonitors said:


> I have used a standard dimmer switch as a thermostat to lower temps on a basking spot no automatic adjustment though so you have to fiddle with it a lot...


Its not a thermostat though is it as it wont control temperature at all.


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## mrhoyo

The septics use dimmer switches and call them rheostats. I can see how it would work but it would be useless if room temps changed. Id much rather spend the extra money on a stat. At least you know the temps will be in a set range


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## Spyro695

why not just a house thermostat - they r only about £6


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## reptiles-ink

Spyro695 said:


> why not just a house thermostat - they r only about £6


 With a house thermostat you would need to have the unit inside the viv as the temperature sensor is inside it.
Also a lot of house stats dont go high enough for a lot of snakes.


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## joe_houghton

*Sorry to bring up an old Thread.*

Sorry to bring up an old thread, but I am trying to make my own thermostat with LCD screen (and build this into my Vivarium; which I am yet to build).

Below is my parts list (which the total is £30)









You may be thinking - why bother if it costs more than a Habistat?
Well, I would also like two Digital Temperature probes (£4 each on ebay) plus this is a hobby and keeps me out of trouble 

Basically I need some help making sure I have selected the correct parts and knowing how to connect each item together (i.e. pin outs). 
I'm willing to take pictures and document and share code of how I put this all together. Oh by the way I am a low level software engineer and have worked with PIC's before but have never designed a circuit board.

ANY help will be gratefully appreciated. 
Joe


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## Devon_Paul

Magpye said:


> This probably doesn't help, but:
> 
> Thermostat Kit
> 
> attached to:
> 
> Temperature Module
> 
> Thermostat for under 20.00


That thermostat module only goes up to 30 degrees C (86F) so it may not be suitable for most reptiles.


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