Recordable Motion Sensor Sounds

paddylonglegs

Hope this is the right thread -

I want to build a motion sensor that will play my own sounds that i recorded myself. Could anyone point me in the right direction of where to start and where to source parts from? I am planning an exhibition, for each of the exhibits there will be recorded information that will be activated when people walk past. I would prefer not to have any computers hooked up to it if possible.

Thanks

spideog7

I'd say the simplest way would be to pick up a few crappy MP3 players, something nobody wants anymore like 128Mb or 256Mb. Record your sounds in just one MP3 file for each player and put it on to it. Connect the player to a small set of speakers in front of your exhibition, make up a little motion sensor circuit using a light dependent resistor or something and hack it to the play button. Set the player up to play it just once every time the play button is pushed.

The actual circuit should be fairly straight forward, you can just use a FET or Transistor setup to behave as your play switch and a small speaker can be got in Maplin for a few euro.

paddylonglegs

spideog7 wrote: »

make up a little motion sensor circuit using a light dependent resistor or something and hack it to the play button. Set the player up to play it just once every time the play button is pushed.

The actual circuit should be fairly straight forward, you can just use a FET or Transistor setup to behave as your play switch and a small speaker can be got in Maplin for a few euro.

Great spideog, this sounds like exactly what i need, but i really have no idea about how to hack the circuit board with the motion sensor.have googled a few possible ways to do this but i really can't understand it.maybe a bit more research is needed

spideog7

Here's a crude 'motion' sensor:
http://www.discovercircuits.com/H-Corner/shadow.htm

You could also do something with a Light Dependant Resistor or Diode in a tube to detect shadows.

In the circuit above you would just take the branch on the far right, get rid of the 'beeper', the +9v and the gnd and literally solder these two wires in place of the play switch on your MP3 player. It's a pretty crude way of doing it but it should work. In this arrangement Q1 is setup to behave like an on/off switch. Simply put when the voltage rises high enough on it's input pin it connects it's two output pins together (not exactly but just imagine it works like that). It might work better if you used a transistor in place of Q1, in which case you'd just put a resistor in series with it and play around with some of the components on the output of the op-amp.

http://www.rason.org/Projects/transwit/transwit.htm

The only problem you may have is multiple firing (if it's a play/pause switch you'll end up pausing it again by accident if it detects another shadow). To solve that you might have to put in some sort of simple electronic timer (555 circuit) between the output of the op-amp (where the pulse is shown on the circuit above) and the 'switch' that delays sufficient time to allow your message to play and let the person to walk away before allowing the switch to be strobed again.

Like I said it's a pretty crude solution but just try to keep it simple and it should work.