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TirthankarMukherjeePIC
01-20-2008, 03:15 PM
Will it be possible to detect a flame of candle with LM35 (-40 to 150 C) ?? Any Idea any one ... seniors please comment...

allbits
01-20-2008, 05:46 PM
LM 35 needs contact.

It is not recommended to detect flames.

TirthankarMukherjeePIC
01-20-2008, 09:16 PM
Then what is the solution ... what IC must be used... it must be available in India..

MohitM
01-20-2008, 11:08 PM
Flame temperatures are upwards of 1200-1300C. You'll need something like a pyrometer or an IR thermometer to measure such temperatures.

TirthankarMukherjeePIC
01-21-2008, 12:43 AM
Basically I need to move towards the flame ... Pyrometer and IR thermometer are very costly... its impossible to use for my project ... any way to move my bot towards a flame ... ?

MohitM
01-21-2008, 10:06 AM
See, Tirthankar, its these kind of questions that irritate a lot of us up. You begin by asking "Will it be possible to detect a flame of candle with LM35" and now you tell us that you want to detect a flame so that a robot moves towards it. Both are questions for vastly different applications. You should instead frame questions that give as much information as possible in a reasonable amount of words.

By the time the inquirer gets to actual fact of the matter, one is already 3-4 replies down and by that time, most of us have lost interest.

TirthankarMukherjeePIC
01-21-2008, 11:26 AM
See, Tirthankar, its these kind of questions that irritate a lot of us up. You begin by asking "Will it be possible to detect a flame of candle with LM35" and now you tell us that you want to detect a flame so that a robot moves towards it. Both are questions for vastly different applications. You should instead frame questions that give as much information as possible in a reasonable amount of words.

By the time the inquirer gets to actual fact of the matter, one is already 3-4 replies down and by that time, most of us have lost interest.

OK I am really sorry if I was not able to express myself...

elecrom
01-22-2008, 07:55 AM
Hi, Here is my SUGGESTION ( I haven't tried it, just thought abt it)

What is req ?
- You can use normal IR diode with 4.7K fixed res, and 22K trimmer pot

How to do ?
- -------------VCC
|
---
/\ (sensor diode)
|
|
<
> (4.7k, R1)
|
|------------------------------------>> [Vin] TO ADC or comparator
|
[/] (22K trimm, R2)
|
|
--------------- GND


- Keep sensor to distance X from flame pointing right towards it. Now adjust trimmer to get desired minimum sens voltage. Note this must be suffieciently high so as to overrid any stray IR present in ambient light.

- sample this in ADC / comparator . If Vin>Threshold, flame has been detected, else not detected.

- Now, to move towards the flame, you need to have some spatial resolution.

- So use 2 such sensors seperated by approx 10 cm from each other.

- Now use logic similar "line follower" logic to keep robo-car pointed towards the flame while moving forward.

TirthankarMukherjeePIC
01-23-2008, 08:03 PM
Thanks Bro...

Little bit more discussion .. hope Mohit doesn't get angry ... but I dont blame him .. nway it was my fault...

I need to prepare a working model of a fire fighting bot... so the source of heat is in my hand :D ... if detecting candle becomes difficult .. I would use a room heater/hair drier ... so that I can detect the hot region ( or what realistically happens during a fire...)

I am trying to simplify the problem a little bit so that I can put my source of heat behind some obstacles ... then my bot will avoid the obstacles and reach the goal ( heat).

allbits
01-23-2008, 09:07 PM
A Flame emits far more IR than a heat source, like a hair dryer - You will need to have a sensitive thermal camera to detect them at a distance.

And you are yet to mention the distance at which you want to sense it!!

(Which is the most important parameter while designing things of this sort)

TirthankarMukherjeePIC
01-23-2008, 11:48 PM
5ft to 6ft .. would be more than enough ... but if obstacles are there .. then what would be the solution ...

elecrom
01-24-2008, 07:52 AM
You have to have Line of sight between candle (source of IR) and sensor.

TirthankarMukherjeePIC
01-24-2008, 04:29 PM
do I need to have an IR filter ( that passes all IR and blocks all visible light) ... I hope that photo transistors will work well ... I have some old photo transistor .. a opening in front of it .. with a lens .. I got it for Rs 65 .. at kolkata ... or clusters of normal IR diode will work ... ?

elecrom
01-25-2008, 12:35 AM
dude, forget phototransister, use IR diode sensor, no external IR filter is needed. And one sensor comes for just 5-6Rs.

TirthankarMukherjeePIC
01-25-2008, 11:20 PM
Thanks Bro ... let me try it out ...I will surely let you know... thanks a lot..