arduino and multiple thermo sensor

[philbona]

hello,

I am projecting a kind of woodstove controlling system.

After designing my plan, I realised that I need 18 diff thermo sensors ( K or tmp35)
This quite too much for one arduino uno v.3 as there are not enough analog.

Anyway I cannot believe it shouldn't be possible to do so.

I am not an expert ( far from ), but if something like a multiplexer should be the solution...

if somebody could suggest me a kind of easy solution, it would be great,

thanks,

Philippe

[johnwasser]

If you are using a K-type themocouple you will need some kind of conditioning amplifier anyway.  You can get one with a digital interface (I2C) and use an I2C multiplexer if the units don't have adjustable addresses.

For any temperatures below 125°C you can use a string of DS18B20 OneWire thermometers on a single pin.  Each has a 64-bit unique address.

[philbona]

thanks for your reply,

For the K sensors, I intend to use a RC and OAP.
Your idea to convert into digital sounds nice, I will investigate with I2C
I've found 'Analog/Digital MUX Breakout' on SparkF, with 16 AD ports which seems to be very easy to use. ( still missing two AD ports but I can use those on the UNO, so my problem seems to be solved at this time.

regards,

Phil

[ElCaron]

Why don't you use a digital sensor, like DS18B20?

[philbona]

Good point,

because I already bought the K-type and tmp36 ;-)
but you are right dig sensor should have been better.

thanks,

Phil

[philbona]

...
also, I am not 100% sure that with a woodstove, 125° is sufficent, it MUST but sometime water may boil and reach xxx ° before exploding the tubes.
One reason to create this controlled woodstove.

Just for expl.

woodstove is a non interruptible process. I need to spread the hot water following a prioritised route. But when reaching all the thresholds ( heating circuit, buffer tank and sanitary hot water) where can I divert the excess of t°?

Thanks to these proj. It will advise ( my wife or me ) to stop loading wood BEFORE or to load more,

regards,

[johnwasser]

woodstove is a non interruptible process. I need to spread the hot water following a prioritised route. But when reaching all the thresholds ( heating circuit, buffer tank and sanitary hot water) where can I divert the excess of t°?

You can control the wood stove heat output by controlling the rate it receives oxygen.  You can close the dampers to reduce heat and blow in air to increase heat.

[philbona]

oulala,
new item in my project,
oxygen control ? yes i  will investigate
blowing or reducing the air input ? wouh, it's a very basic woodstove,
only manual intervention is possible to reduce the ventilation, otherwhise putting new diy mechanism on it and...
my wife will be ...
I don't know how you say that in USA,
Hmmmm,
say strange

phil