Help with Inexpensive Pressure-Activated LED Lighting Project

[WaySafe]

I am very inexperienced at wiring, and electricity in general, but was hoping to find some assistance in this forum.

I am looking for a fairly inexpensive way to wire an LED to turn on when pressure is put on some type of sensor (not sure what would be needed). When there is no pressure, I want the LED to be off. For example, if you can imagine a spring holding up a piece of wood, and when something is placed on top of the wood, the spring bends, allowing for two wires to touch and light up the LED. Like I said I am very inexperienced and do not even know if this is a possibility, just an idea.

Some specific questions:

Is there any way to wire an LED so that pressure creates an electric current without the use of a battery or power source?

and if so,

What materials would be needed, and where could I find them?

I appreciate any and all advice, and look forward to possibly using your assistance for my first electrical project.

 

[dlgoff]

I am looking for a fairly inexpensive way to wire an LED to turn on when pressure is put on some type of sensor (not sure what would be needed). When there is no pressure, I want the LED to be off. For example, if you can imagine a spring holding up a piece of wood, and when something is placed on top of the wood, the spring bends, allowing for two wires to touch and light up the LED. Like I said I am very inexperienced and do not even know if this is a possibility, just an idea.

Sounds like a good place to use a http://en.wikipedia.org/wiki/Micro_switch" .

Is there any way to wire an LED so that pressure creates an electric current without the use of a battery or power source?

No. However there are http://en.wikipedia.org/wiki/Piezoelectricity" that will generate a voltage when a force is applied. Don't think you will get enough current for your LED; unless you have lots of force.

 

[negitron]

Something like this might work; just replace the audible alarm with a battery and your LED along with a series resistor. But, it depends on how sensitive you want your setup to be. It might not work if you want to sense the weight of, say, small animals as opposed to people. Tell us more about what you're looking to do.

 

[WaySafe]

I am trying to build a trap (metal frame), that when an animal has been caught, the light turns on, alerting me of the animals presence. I was thinking of putting a spring on the bottom part of the cage where if the animal steps on it, the spring bends, setting of some sort of mechanism turning the light on. It is just an idea I had for fun, and I have recently become interested in electrical engineering and figured its a cheap project I could work on to get myself acclamated. I would like the sensor to be small enough to be indiscreet on the cage.

dlgoff:

Is a microswitch small enough for me to attach to a metal rod on the cage? And does the microswitch turn the light off when the pressure is released?

Also which type of wiring could be used between the switch and the LED light? Is there a type of tape wire that could be taped to the metal instead of loose wiring?

 

[vk6kro]

Microswitches are quite small.

You could have the gate of the trap compressing the microswitch when it was open. When the trap is sprung, the gate closes and the microswitch is released. Microswitches can have double throw switches in them, so you use this to turn on the alarm. Just wire the switch so it is normally on, and off when it is compressed.
This way you keep the electonics well away from the animal.

The alarm could be controlled by a monostable 555 or 74C221 if you only wanted a brief sound.

You can get ribbon cable which you can strip pairs of wires off. These would lay flat and be easily taped to a cage.
You can also get heat shrink tubing which you put the wires in and then heat with hot air to shrink it onto the wires.
Or you can just use ordinary "spaghetti" plastic tubing which fits over a bundle of wires to hold them together.

 

[dlgoff]

dlgoff:

Is a microswitch small enough for me to attach to a metal rod on the cage? And does the microswitch turn the light off when the pressure is released?

Also which type of wiring could be used between the switch and the LED light? Is there a type of tape wire that could be taped to the metal instead of loose wiring?

Take a look at this wikipedia page showing http://en.wikipedia.org/wiki/LED_circuit" . To turn it on and off, just put a switch (micro or otherwise) in the loop.

You can tape a pair of switch wires to your cage out to the LED circuit.

 

[negitron]

Take a look at this wikipedia page showing http://en.wikipedia.org/wiki/LED_circuit" . To turn it on and off, just put a switch (micro or otherwise) in the loop.

And remember to use the correct type of switch; if you want the LED to come on when the switch is depressed, you want a NO (normally open) type but if you want it to come on when the switch is released, you want a NC (normally closed) type. Some switches offer both types with three terminals: one is a common, one is a NO and one is a NC.

 

[WaySafe]

Thanks for the help, let's hope this thing works out for. I appreciate everyone's input.