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Author Topic: As fast as an NFL player?  (Read 3750 times)
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ultrasonic sensors

though with lasers if you get shot in the eye your inclined to shut it, with invisible light you never know when its blinding you, guess it depends on the distance apart and the intensity of the light ...

though honestly I don't see why you couldn't do it with just normal light, even NFL players are not running faster than most light sensors
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ultrasonic sensors

though with lasers if you get shot in the eye your inclined to shut it, with invisible light you never know when its blinding you, guess it depends on the distance apart and the intensity of the light ...

With an IR laser you'd probably know once the searing pain hit. Honestly no one can shut their eye fast enough. A buddy of mine got a 2 or 4mW pen and was sweeping it across a near wall when the beam hit a small curved (fisheye? it curved outwards) mirror. The then spread-out reflection caught him in one eye and it was about 2 hours before he could see anything but red from that eye. Scary stuff. Think of what a flat window might do? Or a polished button?

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though honestly I don't see why you couldn't do it with just normal light, even NFL players are not running faster than most light sensors

The 'hard part' is blocking out background light from the sensor.
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I don't use lasers myself, but the more I read about the potential for severe permanent optical damage the more I'm inclined to say that you want to keep things like this well away from children - and grownups too, I suspect.
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I don't use lasers myself, but the more I read about the potential for severe permanent optical damage the more I'm inclined to say that you want to keep things like this well away from children - and grownups too, I suspect.

FFS. A typical laser pointer isn't going to cause permanent eye damage. If you're going to insist that it can then please provide a citation.

These hazards are no worse than camera flashes, welders, or mirrors on a bright day, but if you're extra paranoid then it's trivial to just choke the current to the laser to the minimum that you need.
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Yeah there's no liability for making someone wander around for hours unable to see from one eye, is there? I mean, since it's not permanent, right?


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I don't use lasers myself, but the more I read about the potential for severe permanent optical damage the more I'm inclined to say that you want to keep things like this well away from children - and grownups too, I suspect.

FFS. A typical laser pointer isn't going to cause permanent eye damage. If you're going to insist that it can then please provide a citation.


FFS. A laser pointer is obviously potentially dangerous [1][2]. If you're going to insist that it cannot be dangerous under any circumstances then please provide evidence.
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FFS. A laser pointer is obviously potentially dangerous [1][2]. If you're going to insist that it cannot be dangerous under any circumstances then please provide evidence.

Both of your citations refer to high power lasers.
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If you read the article looking for other than excuses to play then you might see where trouble can happen.

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Possible more potentially damaging -- although not to the eye -- is that a regular pointer laser can overwhelm the eye with light, typically called flash blindness. If a person is walking a rocky path, operating machinery, a vehicle or aircraft, this temporary loss of vision could cause injury or disaster.

If you want to be sure, ask an ambulance-chaser.
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Both of your citations refer to high power lasers.

But 'high power' only means a couple of mw, which is only a tiny step from the power levels that are being discussed and easily achievable with the hardware being discussed. I noticed that green lasers were specifically mentioned as problematic due to being higher power than specified, and those were recommended earlier in the thread.

I accept that these lasers can be safe under the right circumstances, but I also maintain that they can be dangerous under the wrong circumstances and the possible consequences can be nasty. To dismiss that danger and simply assume that the system being developed will be safe for a youngster to play with seems quite risky to me.
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I agree with you guys that (any) laser can potentially be dangerous to someone vision.

If the OP insist to use a small laser ( a pointer type ). I will shield it with a toilet paper roll <-- the cardboard roll , and shield the receiver with a toilet paper roll <-- cardboard. Install them about 1'' to 2' height from the ground. <-- I feel it is a safe height. Just hope a child is not going to look into the tube because he/she is currious about the "stange" set-up. <-- my worry   
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Do the run at the right time of sunny day you only need a light detector anyway. Guess why?

Errrr, make that two light detectors.....

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Wow a lot of replies since my last post. We are going to proceed with the lasers, but I also like the idea of the string. I have no idea how I would do that, but that might be fun to try at some point.

We got the transistor working, although visualizing the circuit was a little bit of a challenge for him. Now he understands how it works. Here's a picture of the laser we're using with the transistor.

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@atrodad

Well. Not bad. gnd and from a ~ pin 10 is OK. External battery for the lase is OK. Can you tell me what type and number of the transistor you are using ? at the base ? I see a resistor and connect to the collector ? . Did you connect : 1. base limiting resistor.
2. current limiting resistor.

I know, sometime, it is hard to follow a schematic going to a breadboard.

Here a picture of a typical transistor connection. Sorry for a bit "out of focus"

In the picture, I use color code for my connection. Red is positive. Green is gnd / commun. I use a fiber optic transmitter. ( a IR led ) The limiting resistor is 68 ohms. The base transistor is 4.7 K. And the transistor is NPN - 2N3904 - EBC type. My circuit is connect to a FDTI USB board.


* transistor.jpg (100.61 KB, 1024x768 - viewed 8 times.)
« Last Edit: February 04, 2012, 12:56:54 pm by Techone » Logged

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The thing is that on a day bright enough to cast shadows..... or even have a light-colored sky....


« Last Edit: February 05, 2012, 01:52:18 am by GoForSmoke » Logged

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@atrodad

Well. Not bad. gnd and from a ~ pin 10 is OK. External battery for the lase is OK. Can you tell me what type and number of the transistor you are using ? at the base ? I see a resistor and connect to the collector ? . Did you connect : 1. base limiting resistor.
2. current limiting resistor.

I know, sometime, it is hard to follow a schematic going to a breadboard.

Here a picture of a typical transistor connection. Sorry for a bit "out of focus"

In the picture, I use color code for my connection. Red is positive. Green is gnd / commun. I use a fiber optic transmitter. ( a IR led ) The limiting resistor is 68 ohms. The base transistor is 4.7 K. And the transistor is NPN - 2N3904 - EBC type. My circuit is connect to a FDTI USB board.


Thanks for the info. I should have used a color code, that makes sense. The transistor is also a 2N3904. I think I used a current limiting resistor--1 kOhm.

I need to drive two separate lasers, though. I'm assuming it's better to use two separate transistors utilizing two separate pins to switch them?
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