Made a PLA smoke detector cap and it set it off

[Oliveros 11]

Hello Everyone,

 

Got a bit of an odd question based on an odd experience.

 

I made some black smoke detector caps in an attempt to get some cheaper than $5 a piece, since We're looking to get a whole bunch of them and I can print them for $0.17 a piece in a printer.

 

It's a photoelectric sensor with an eye inside and if that sensor's shot gets interrupted or dispersed, it triggers the device and puts it into alarm.

 

So I made some and went to try one and it set the device off as if there was smoke all over it, I made it out of Bumat PLA, there was no logical reason for it to have happened but now I'm wondering why it happened.

 

Any of you guys have any experience on this? Original cap looks like the attached picture.

 

 

[Mari 33]

... maybe first Google how a photoelectric sensor works...

 

The original orange cap seems to be translucent, the black one you printed isn't! Don't play arround with smokedetectors, better be safe than sorry!

[Oliveros 11]

I did, the light originates from within the detector, I tested it on other ones with no problems.

 

If you turn the lights off in a room and close the doors and there's no windows, the smoke detector doesen't go off, so the idea of the new cap blocking all light crossed my mind but didn't make much sense in the end.

 

Can't seem to get another one to go off, perhaps the detector itself was faulty.

[Mari 33]

The "lightsource" is inside the smoke detector so it doesn't matter if you turn on/off the lights and if there is a window or not. 

Quote

In an optical point smoke detector there is a photodiode and a light source. When smoke is added, the light is disrupted which is seen by the detector. In the direct method, the light source and detector are directly opposite each other. In the absence of smoke, light can easily reach the photodiode. If smoke particles are present between the light source and the photodiode, the amount of incident light will decrease and the detector will sound the alarm. Most smoke detectors work according to the indirect method. The light source and the detector are diagonally opposite each other. In the event of smoke, the light bounces off the smoke, causing more light to fall on the detector and sounding the alarm. An internally polluted smoke detector that works according to the direct method will, in principle, become increasingly sensitive and alarm.

 

[Oliveros 11]

Right, I'm aware of that.

 

The cap should have no effect on it's function, which is why it's odd. 

 

It was a one off, tried putting the same detector in and tried it with the same cap, nothing happened. Tried 3 other smoke detectors, nothing happened.

 

People put blue tape, electrical tape, plastic bags, foil tape, etc. on these things and it doesn't set them off, but for some reason, this one time, it did for whatever reason.