Temp Controller Circuit

[bryan1]

Hiya Guy's,
I'm on making up a hot box for my wife's plants, when I say hotbox I mean it's just a heat controlled box to help raise seedlings in winter. Now I've made up the box and cart as it's nearly 1/2 a cubic metre in volume. The base will be enough to hold 3 trays and I have a 20 metre length of hydronic heating wire with an alumium sheath so it can be used in a wet enviroment. The wire's resistance is just 0.2 ohms a metre by the spec's and the length I have is 4.78 ohms measured off my fluke multimeter. The temperature my wife is after is a max of 20 degrees C and rather than use a digital temp sensor and micro-controller I've been looking on the net for a simple thermistor based cicuit which I could pot to stop moisture getting into the circuit. So far all I've come up with using google is commercial products so would any of you guy's be able to either provide some links to sites or explain the best way to tackle the circuit. I'll be using a 12 volt 200 amp hour battery I have spare and I'll be connecting the battery to a wind genny I made so it would be automatic.

Cheers Bryan

 

[Nigel Goodwin]

Hiya Guy's,
I'm on making up a hot box for my wife's plants, when I say hotbox I mean it's just a heat controlled box to help raise seedlings in winter. Now I've made up the box and cart as it's nearly 1/2 a cubic metre in volume. The base will be enough to hold 3 trays and I have a 20 metre length of hydronic heating wire with an alumium sheath so it can be used in a wet enviroment. The wire's resistance is just 0.2 ohms a metre by the spec's and the length I have is 4.78 ohms measured off my fluke multimeter. The temperature my wife is after is a max of 20 degrees C and rather than use a digital temp sensor and micro-controller I've been looking on the net for a simple thermistor based cicuit which I could pot to stop moisture getting into the circuit. So far all I've come up with using google is commercial products so would any of you guy's be able to either provide some links to sites or explain the best way to tackle the circuit. I'll be using a 12 volt 200 amp hour battery I have spare and I'll be connecting the battery to a wind genny I made so it would be automatic.

Try googling for "741 tutorial".

 

[bryan1]

Try googling for "741 tutorial".

Hiya Nigel,
Thanks for that tip mate the first link in google took me to Tony Van Roon's site and sure enough the fan circuit based on the 741 would be ideal

Cheers Bryan

 

[Nigel Goodwin]

Try googling for "741 tutorial".

Hiya Nigel,
Thanks for that tip mate the first link in google took me to Tony Van Roon's site and sure enough the fan circuit based on the 741 would be ideal

I know! 8)

"555 tutorial" is a good google as well!.