Laser Sensor button?

[Spacehonkey]

I'm not sure how to explain what I want exactly but I'll give it a shot.

For one of my future projects I want to make the PWR, RESET and DVD DRIVE buttons completely different. I was wondering if there is a way to make the buttonS to the computer into a type of laser mechanism. Another way to put it lets say you put your finger or hand in some type of hole and it brakes some type of laser and then activates whatever. I was thinking along the lines of a laser security system when you brake the beam it sounds the alarm. Well I figured this would be the best pool of knowledge to see if anyone knows of a way to pull this off.

[Guardian]

i'm not sure what you're tryina get at, but you could somthing like a touch screen?

[Spacehonkey]

Let me try to explain it in a different way then.

I want to be able to turn my computer on by sticking my finger in a tube but not really touch anything. There would be a laser of sort and when you brake the laser with your finger it would activate the power button.

[Ironcat]

If you want to build a really BIG computer than you could just buy some sort of a garage door sensor.
You could mount it inside and just leave a whole drive bay open.
Invent some gobbledeegook about the computer scanning your palm for security, insert your hand and when it breaks the plane of the beam the garage door opener could be triggered to activate the computer and you'd amaze all your friends and neighbors.

[Spacehonkey]

If you want to build a really BIG computer than you could just buy some sort of a garage door sensor.
You could mount it inside and just leave a whole drive bay open.
Invent some gobbledeegook about the computer scanning your palm for security, insert your hand and when it breaks the plane of the beam the garage door opener could be triggered to activate the computer and you'd amaze all your friends and neighbors.

Not a bad idea. I won't be building anything that huge but maybe braking open the laser safety switch on the garage door and scale that down might work.

[Airbozo]

You could do this with a led and a photo voltaic sensor (a light sensor) and a small relay circuit. Finger breaks the beam, relay makes contact...


EDIT: Exactly like the sensors that go off when you enter a store. Break the light beam, bell rings...

EDIT2: Similar to this circuit although it is just a light sensor circuit;
http://www.uoguelph.ca/~antoon/circ/sensor2.htm

EDIT3: More info here (some info that just6 does not apply too);
http://ourworld.compuserve.com/homep...epage.htm#menu

EDIT4: and even more;
http://home.cogeco.ca/~rpaisley4/PhotoDetectors.html

[Spacehonkey]

Thx, Airbozo, I think that might actually work for what I have planned.

[Guttenaffe]

not that hard if you use the 5VSB

You don't really need a "laser" but an LED with an photodiode (or maybe a photoresistor will work too) connected to the control LED of a optical isolator. As follows:

As long as the photodiode is saturated to ~0Ω the photo you have dual 0V across the operating LED of the optical isolator. If you block the saturation to the photo diode then current can power on the 4N25's LED and trigger the its transistor to operate as your switch. This is at most a $5 circuit...

[Spacehonkey]

I chose to try and make the light activated switch by following these schemetics

http://www.uoguelph.ca/~antoon/circ/sensor2.htm

I went to RadioShack and bought all the stuff I needed to complete it but I forgot to get a 12 Vdc pwr supply.

Does anyone know of a good place to buy a cheap 12Vdc pwr supply?

I called RadioShack back and the cheapest one they have is $43. Maybe I should just wire some AA batteries into series and use that. Yeah maybe I'll try that instead.

Oh yeah also has anyone out there ever messed around with a Light Dependent Resistor?

I want to test out the Light Dependent Resistor to see if it was good so I started to mess around with it and hooked it up directly to a 6Vdc pwr source with nothing else to interfer with it and used a meter to get it's measurements. Now maybe I'm all jacked up in the head but when you shine a light on the resistor shouldn't it NOT let any power pass through it or at least decease the voltage. When I did it I shined the light directly on the Light Dependent Resistor and nothing changed. I still got 6Vdc coursing through it just like before I put the light on it. If I'm doing this wrong can someone please explain how it should work.

[Drum Thumper]

Does anyone know of a good place to buy a cheap 12Vdc pwr supply?

Would a wall wart work? 15 buck at the most at your local wally world.