Passionate about trash

Hi - I know very little about circuitry, but I'd love to tap the brains of some smart people to build the "world's deepest bin" just like this:

I would guess light sensors, speaker, battery (or solar-powered). If it could be programmed to do something other than solely play the 'falling sound' then it might have more utility. E.g. tell the time, read a horoscope, play some advertising, play a joke (from a library). But 'd be very happy with the falling sound as a start!

It needs to be cheap so that theft isn't a huge loss.

I figure if there was a bunch of intelligent folk anywhere able to do this, it's here :)

I would suggest you learn more about circuitry, you cant expect other people to do it entirely for you. I would recommend you get a Arduino and a sonar sensor and try to sense objects. That would be a nice start and you could implement a speakjet or something from there.

I figure if there was a bunch of intelligent folk anywhere able to do this, it's here

There is no shortage of good ideas in the world. There is, however, a shortage of people to execute those ideas.

I think I'm pretty good at putting things into motion e.g. actually getting them fitted into trash-bins after liaising with city councils, but it would take me an age to learn enough about circuits to design something that fits the purpose. I couldn't do it all quickly enough, hence the request for some aid.

But I have done some background reading and have some questions:

Sonar sensor vs. Light dependent resistor

Sonar sensor:-

standby 110mA in use 2 amps

How long between pulses would be an acceptable time period? A piece of trash can be placed in the bin in half a second, thus a pulse every quarter a second might be needed.

Would I need a capacitor to handle this jump in power requirement? If so, should I power this from a separate source rather than risk the microcontroller losing too much power?

Cost about $30

Light dependent resistor:-

Inexpensive, less-power needed for detection(?). The problem I can see here is that as light alters throughout the day, activation may occur when the sunlight changes, or a clous passes. Thus, would it be possible to calibrate it based upon rate-of-change of resistance (the change in power)?

I love the sonar-sensor and speakjet chip, although a little pricey if stolen.

I'd be happy with the falling sound if it was effective, and then maybe progress onto the sonar-sensor and speakjet chip if it proved popular and needed tweaking to keep it popular in the same location.

Sonar sensor:-

standby 110mA in use 2 amps

Are those for boat sonars?

That's a lot of current - I would have said more like 50mA operating and 5mA idle, for a hobbyist-grade sonar.