Challenge for more experienced DIYers

[Willthebold]

Hey guys, this site's always been a ton of help so I thought maybe you guys could help me out with this little project.  Basically what I need is a circuit that is set off by some kind of motion sensor.  After it's set off, what I need is for it to turn one switch on and to also hit a momentary switch once a few seconds after the first switch.  It's kind of a weird idea, but I think it could lead to some interesting possibilities.  What kind of circuit and motion sensor could I use for something like this?  Thanks in advance for all the help. 

[The Tone God]

More information would be handy. What is the sensing distance ? How large an object ? What are the properties of the object to be sensed e.g. Colour, size, density, reflectivity, state, etc. ? What are the environmental conditions ? Are there size and cost constrictions ?

Andrew

[Willthebold]

Well, just enough to sense like an arm waving from a few feet away.  I'd like to keep the cost down as low as possible.  I remember having seen some really simple sensors in novelty christmas wreaths that would trigger music.  I could use something with that kind of sensitivity, but instead of triggering music, it would trigger the two switches in succession.  I just don't know how to go about building the circuit to do that kind of thing.  I know there are some circuits like the millenium bypass that switch things using transistors or something, but I don't know exactly how they work.

[petemoore]

  It takes my pedals a while to light their LED's [which can be used for switching purposes w/LDR's], this is caused by the capacitors in the PS and the added bypass caps on the circuits.
Basically what I need is a circuit that is set off by some kind of motion sensor.  
  I can't tell you much about this part. Except the simplest type of motion sensor, a switch...like that you see at grocery stores hidden under the floor mat in front of the automatic door.
  Another would be a laser/photosensor like garage door, I wouldn't recommend it for stage applications.
  A magnet in your shoe, a magentic sensor made available.
  After it's set off, what I need is for it to turn one switch on and to also hit a momentary switch once a few seconds after the first switch.  It's kind of a weird idea, but I think it could lead to some interesting possibilities.  What kind of circuit and motion sensor could I use for something like this?  Thanks in advance for all the help 

[charbot]

Check out this place: discovercircuits.com


look under schematics ....then " S" for sensors.    You can make something pretty simple using a LDR and some other parts all found at RatShack.   The LDR can detect shadows (waving hand) and triggers a relay. 
Be creative.  Use simple circuits like building blocks.... Try building a separate "off after delay"  circuit  and then adding it to the motion sensor. 

  I did a art piece, called "Are You Going To Hell ?", where a touch sensitive plate triggered a "coin toss" circuit that randomly lit one Led or another.  Each LED was shrink wrapped to a separate  LDR / rely  and delay-off module, ultimately turning on a randomly flickering "flame "  devices that. depending on which one was triggered,flashing leds lit up the word HEAVEN or HELL for a few secs,giving the viewer  his eternal judgement.  the leds turned off a few secs later.   All the electronics were stuffed inside  a frame and behind a reverse glass painting.  the whole thing  sort a looked like the back of a pinball machine.... 

....Anyway,  everything was made on little 2'' x 2'' perf board squares and all wired together.
Also look for forrest mims "getting Started in electronics" .   All the schematics I used were either from discovercircuits.com or in that book.  most are both.

[Willthebold]

Thanks guys.  I've been looking around discovercircuits and came across this too....  http://www.discovercircuits.com/DJ-Circuits/montionalarm1.htm
I think it might be what I need.  I just have a couple questions about it:  When it says that you can use a 9 volt battery for it, does that mean you can use it as is without modifying?  Also, is the voltage supplied to the buzzer the same as the circuit voltage like 9 for a 9 volt battery?  And one more, when this circuit is triggered, does the buzzer stay on, or does it just buzz while the piezo is tripped?  Thanks again.

[Paul Perry (Frostwave)]

I expect those Xmas werath things actuate the same way as my plastic toad door alarm: there is a lens focusing onto a LDR (or possibley a phototransistor) so that if ther eis a sudden change of brightness (an edge in the image moving past it) the voltage is differentiated to give a peak & if this is above a threshold it triggers a monostable gate (maybe 555 timer based).

The problem is going to be making it 100% reliable.
Personally I would go for a light beam that you interrupt, provided it is possible to arrange things that way. If you look at some shop door alarms, it is a beam that goes to a mirror& back.
So you could have a mirror on a mic stand - or something else stable - and put the unit on an amp, for example.
But you know, in show biz anything is fair.. you could have an unobtrusive floor switch (even one of those alarm mats) and just happen to stand on it as you wave your arm!!

[Willthebold]

Ok, so I bought a cheap little motion sensing device that sounds an alarm when you pass in front of it.  I think this will work, but I need the voltage it puts out to be a little higher.  The voltage going to the speaker when it sets off is only about .2 volts and I need it to be more like 5-6 volts.  There are a couple of transistors around the connections to the speaker.  Would one of those be fed a higher voltage which the transistor would use to drive the speaker?  I just need to find a voltage source that is only present when the sensor is tripped.  Thanks again for all the help.

[Willthebold]

Follow-up : Maybe if I could just get a really low voltage relay that would trigger on those small voltages and run everything off that?  Do they make relays that work off of just a tiny voltage?

[Willthebold]

One more thing: I've heard about using a transistor to switch voltages.  Would I be able to use that fluctuation of about .2 volts to saturate the transistor and switch a higher voltage to the relay to switch it?  If I could, how do I figure out the values for the resistors going to the transistor?

[Paul Perry (Frostwave)]

Somewher ein that unit there will be a point that swiches by more than .2V, I swear.
But you will have to keep measuring away & turning it on & off till you find it...

[Willthebold]

That's what I was afraid of.  Woult it help if I could get the schematic?

[Paul Perry (Frostwave)]

I would be very suprised if you could get the schematic, but if you do, I'm sure someone here will suggest where to look for a useful voltage.

Personally, I'm still backing the pressure mat approach. I mean, what is more dramatic than turning on a FX by leaping into the air - and onto the mat!

[QSQCaito]

I hope this is of some help:
http://www.web-ee.com/Schematics/Motion%20Detector/UltrasonicMotionDetector.pdf

You could put a light directly pointing to an LDR; so when you put your hand in between the ldr activates a relay(one switch) timer.. and the other switch.