Sensor advice

[Jessica Murphy]

Hi everyone,

I am new to the Hackspace and have a project where I am creating a single person immersive experience as part of my final degree show piece.  I am looking for some advice on what sort of sensor I should use to trigger music and sound controlled by an arduino.

To explain the concept, a single person enters a drum like shape suspended from the ceiling, into a hole that is 75cm across; so their shoulders and arms are inside the drum shape.  I've attached a photo to hopefully make it a bit clearer. Once people enter the space, I want a loop of arduino controlled LED strips and music to be triggered by some sort of sensor and to also turn off once they've left.  I hope this makes sense!

But I'm not sure what sort of sensor to use and how hard they would be to install?  Would infrared be the simplest?  What sort of range can you get on them - I presume it must vary?  I considered a pressure pad but the ones I have seen need to be plugged in so having that at ground level wouldn't be appropriate for my project.

I was going to drop in tonight but unfortunately can't make it but I am hoping to come to the next fortnight's meeting.  I have actually been once before and James Cadman kindly helped my friend with her string of LEDs.

All help is MASSIVELY appreciated, and I hope to drop into the next session!

Thanks very much,

Jess Murphy

PS excuse the messy studio in the picture!

[Nigel Worsley]

The first thing that spring to mind is a break beam detector. They
usually consist of two parts, an IR emitter and a detector, and when
an object prevents the emitter's pulses being seen by the detector you
will get an output signal. There are more sophisticated ones that have
the emitter and detector in the same housing and use a reflector to
bounce the beam back. This type is common in security systems, but
probably a bit expensive for your requirements.

Maplin have a kit available for a tenner:
http://www.maplin.co.uk/p/mk120-ir-beam-break-detector-ll64u but you
can get something ready made from eBay for a bit less.

If you want to go really flashy then use a distance sensor above the
person's head, you could then adapt the show dependent on height (eg.
for kids) or go completely nuts and winch the whole drum up and down
so that eye level is in the right plane!

Nigle

[Ian Lewis]

What about one of those toilet air fresheners with the PIR in. You could
strip one of those down. Mount the sensor just level with the hole, so it
triggers when something comes in the hole?

Ian

>--
>You received this message because you are subscribed to the Google Groups
>"Not Just Arduino" group.
>To unsubscribe from this group and stop receiving emails from it, send an
>email to not-just-ardui...@googlegroups.com.
>To post to this group, send an email to not-just...@googlegroups.com.
>Visit this group at http://groups.google.com/group/not-just-arduino.
>For more options, visit https://groups.google.com/d/optout.

[Nigel Worsley]

> What about one of those toilet air fresheners with the PIR in. You could
> strip one of those down.

No need, the sensors are available as modules eg.
http://www.seeedstudio.com/depot/PIR-Motion-Sensor-Large-Lens-version-p-1976.html
These aren't ideal, however, as PIRs sense movement rather than
presence so if the person gets bored and leaves then the show will
carry on until the end instead of resetting ready for the next person.

They could be used for detecting people approaching the exhibit
though, and perhaps triggering an audio clip that entices them to
stick their head in the drum and see what happens.

Nigle

[Jessica Murphy]

Hi again,

thanks so much for your input, it was really useful!  I think I am going to to for a IR break beam sensor as suggested, mounted on the edge of the entry point so that is trips the sensor/breaks the beam when people enter.

I think it will be something like this - https://www.adafruit.com/products/164

How hard are they to set up you do you think?  I think I described before, but I need it to trigger the music and the lighting loops.

Best

Jess

[Adrian Godwin]

You'll find you get multiple triggers over a period of a few hundred milliseconds, as the person moves into the hole. It can be considered the same as 'switch bounce', a faster effect you get on a physical switch.

I'd write software that notes when the beam is broken and when it's clear again. Once the beam has stayed broken for about 200ms, start the audio. If goes clear again, also for about 200ms, stop the audio and prepare to wait for another beam break (starting the audio from scratch).

You might need to adjust that 200ms figure once you find out how long it takes to enter the drum, and how long after entry you want to trigger the audio.

--

You received this message because you are subscribed to the Google Groups "Not Just Arduino" group.
To unsubscribe from this group and stop receiving emails from it, send an email to not-just-ardui...@googlegroups.com.

To post to this group, send email to not-just...@googlegroups.com.