Re: IR Temperature Sensor

On Mar 4, 11:19 am, Nemo <P...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
tranerm asks

I am attempting to construct a temperature sensor that will activate
several relays when the thermometer senses temperatures above 150
degrees Celsius, or ignition point for decayed wood. Unfortunately I
have only been able to find this plan online, which has far more
features than I need.

http://www.electronics-lab.com/projects/test/023/index.html

If anyone knows of a circuit diagram that would be more to my needs or
has suggestions of any sort, I would be extremely grateful.

If you base your circuit on an IR sensor you will have a lot of
problems, because IR is everywhere. You'll get false positives from
normal lights and even clever circuits which try to auto-adjust for the
average background level can get fooled by, say, a cloud passing across
the sun. Also - how are you going to calibrate it? And protect the high
gain circuitry from RF pickup when someone uses a mobile phone below it?

May I suggest a simpler approach like this:

http://uk.farnell.com/honest-well/t23a150bsr2-15/thermal-switch-nc-15...
dp/1006849

this kind of component, a "thermal switch", is widely available. I used
one recently partly because I noticed this particular shape is some kind
of standard, so even if that manufacturer goes bust Honeywell and some
other bunch will still stock them.

The main problem with this item is that it is normally closed. But if
you're happy to burn a bit of power and continuously power a relay
(20mA?) that's OK. An IR circuit would burn a bit of power anyhow.
--
Nemo

I will be runninf it off a a wall wart so power won't be a problem,
but the interference probably would be. I am trying to build a small
'turret' that will first seek brightness (in a dark room, so for
example, a candle) and then when the IR sensor is facing it if the IR
sensor detects heat above a certain level, activate a series of
relays. One or two of these will shut down the motors moving the
turret, and another will activate a small pump that will squirt water,
extinguishing the flame. From there, if possible I would like it to
seek another target if the detcts temp below a certain level. (however
this is purely an extra) I want to be able to switch the locations of
the candle, so I can't reallly just run temp relays back and forth
either, unfortunately. Thank you incredibly for your help(:
.

Relevant Pages

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