24/12V Two Pins Smoke Detector with Arduino

Projects General Guidance
1

Hi,

I'm working on a learning project that uses 24/12V Two Pins smoke detector, i want to read alarm state of the detector. Usually for this kind projects i'm using 4 pin detectors which are sending short from 3rd and 4th pins so you can read with input_pullup, but i was wondering how things works with 2 pin detectors, so i get 3 working 2 pin detectors to figure it out.

Currenntly i don't have 24v external power supply so i've used cheap 12V/1Amp adjustable adapter to power on the detector.

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As you can see on the picture it says "ALARM CURRENT : 70ma" when i puff smoke to the detector it's led turning red that it means smoke alarm triggered, while it's on alarm mode i've measured the amp and it was 0.01 ma, i've resetted the detector and measured amp on idle mode it was 0.01amp as well, i'm not sure but i think i'm not able to measure 70ma because of my adapter ?

This detector works between 12V & 24v, if i connect GND to arduino's GND and positive cable to arduino's 5Digital port (imaginary of course) it'll damage to arduino due to voltage (right?).

How should i connect this kind of detector to arduino and what should i do to read alarm signal from it ?

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2

The documentation seems to indicate you need to access the internal relay and connect your Arduino to it. All depends on what you want the Arduino to do.

Paul

3

I don't see any mention of 12v.
I do see 24v as a supply requirement.
I don't see any external alarm output.
I do see a note saying "do not repair detector or circuit" and I would say offhand that would probably include any mods.
Apart from that, if it is just an experiment thing, you probably best pick up a signal off the piezo alarm unit, with appropriate voltage divider or opto isolator or whatever.

4

Paul_KD7HB:
All depends on what you want the Arduino to do.

What i want to do is simple, i'll sound buzzer or flash led light when sensor is triggered, i can access internal relay or LED light of the detector to read the state but imagine if you have 5-10 detectors that would be not practicle, there must be a way to read the state of the sensor without opening inside of it.

5

bluejets:
I don't see any mention of 12v.
I do see 24v as a supply requirement.
I don't see any external alarm output.
I do see a note saying "do not repair detector or circuit" and I would say offhand that would probably include any mods.
Apart from that, if it is just an experiment thing, you probably best pick up a signal off the piezo alarm unit, with appropriate voltage divider or opto isolator or whatever.

**I don't see any mention of 12v. -- yes you are right it doesn't mention that, but this brand/model detectors are so much common in my country and using in both 12v & 24v fire alarm systems and work perfectly in both.

**I don't see any external alarm output. yes unlike the 4pin detectors this type sends amps(which i couldn't be able to measure it) to fire alarm system (we call it "SANTRAL" in Turkish) instead of short signal.

**I do see a note saying "do not repair detector or circuit -- well almost all electronical devices has this kind of warnings,if we followed those warnings we couldn't develop any technology or DIY consept would not be invented :slight_smile:

**Apart from that, if it is just an experiment thing -- yes i just want to learn how to read signal from it, fire alarm systems allready very cheap, i don't have any commercial targets about it and bulbs allready invented no need to re-invent again :slight_smile:

6

sheshman:
What i want to do is simple, i'll sound buzzer or flash led light when sensor is triggered, i can access internal relay or LED light of the detector to read the state but imagine if you have 5-10 detectors that would be not practicle, there must be a way to read the state of the sensor without opening inside of it.

If you look at the instruction PDF, it shows a relay in the power circuit. You can do the same. Get a DC relay that will pull in at the 70ma current that occurs when one of the smoke detectors discovers smoke.

Paul

7

but imagine if you have 5-10 detectors that would be not practicle

ok, but what is the actual application in your case? Do you have multiple detectors actually installed and you are trying to do this in the real world, or are you just doing a bench-top experiment to see how this might work?

8

I would have thought that as smoke alarms have both an audible alarm and a visible LED alarm, one could use either.
If none invasive required, then wrap an optical pick up around the LED alarm.

Cannot see how a device rated to work on 24v could work "perfectly" on 12v.

The drama with playing with a smoke alarm, is that it is a life saving device and as such, any mods would be frowned upon to say the least, by authorities.

This is also the case where Arduino is concerned.

Fine if you want to play on your bench, but start installing them anywhere and one could be asking for trouble.

9

Stick a light sensor onto that alarm LED - and there you have your optocoupler! It may not even void the warranty as there's no need to open the case.

10

What @Paul_KD7HB said.

11

steve20016:
ok, but what is the actual application in your case? Do you have multiple detectors actually installed and you are trying to do this in the real world, or are you just doing a bench-top experiment to see how this might work?

i've 3 detectors but not connected all of it, it's just an challenge for me, i'm rookie about electronics and very courious about it, i love controlling devices with arduino and love to learn how things works, that's why i'm spending time to this learning project. They are achieving this with cheap chinese fire alarm systems (which mostly very little main board inside with couple of transistors,leds,resistors & relays) and if they can do it with such small circuits arduino could the same thing and even better.

As i said i'm a rookie and i'm wondering how they did it, for instance Paul suggested

Paul_KD7HB:
Get a DC relay that will pull in at the 70ma current that occurs when one of the smoke detectors discovers smoke.
Paul

i didn't know that there are relays that can pull according to current until his answer, today i'll search and learn about that kind of relays.

@bluejets is quite right and totally agree with him about not to mod emergency devices.

bluejets:
The drama with playing with a smoke alarm, is that it is a life saving device and as such, any mods would be frowned upon to say the least, by authorities.

This is also the case where Arduino is concerned.

Fine if you want to play on your bench, but start installing them anywhere and one could be asking for trouble.

bluejets:
Cannot see how a device rated to work on 24v could work "perfectly" on 12v.

and yes you are quite right but i've seen with my own eyes, there are two types of fire alarm system, one works with 12v other works with 24v, this detector works normally on both systems,i don't know how but it works.

12

Here's the manual that's referenced on the back label of the detector.

Shouldn't this be pretty straight forward? Wire it up as in 1(a) and then use the remote indicator terminals? I don't think that's modding beyond the intended use of the unit.

What alarm panel are you connecting this to?

13

steve20016:
Here's the manual that's referenced on the back label of the detector.

http://www.ssc.ro/manuale/IN338-detector-fum-temperatura.pdf

Shouldn't this be pretty straight forward? Wire it up as in 1(a) and then use the remote indicator terminals? I don't think that's modding beyond the intended use of the unit.

What alarm panel are you connecting this to?

i'm not using any alarm panel, i'm just learning and having fun with arduino,i allready have this manual.

14

sheshman:
i'm not using any alarm panel, i'm just learning and having fun with arduino,i allready have this manual.

This is your problem area as the alarms AND the panel are designed to work together.
My initial suspicion of your quote "12v works perfectly well" is confirmed.

Video here will help you to understand.