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Homemade Red Dot sight Presentation

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Homemade Red Dot sight Presentation

Unread postAuthor: DasAbonnent » Wed Nov 28, 2012 3:17 pm

Hey=)


just wanted to show you the red dot sight i made for my Airsoft Sniper rifle. First of all, it is completely pointless because it generates just a fix point.

It's got a red LED mounted on top of a 45° angeled agryllic glass, that reflexes the point right in the eye of the "marksman".
The red dot can't be seen from the front=)

Because it creates a fix-point, the marksmans eye works as the second point needed for accurate aiming. It's just for cool looking.



/watch?v=1HP0hhGxluE

That's the Video i uploaded about it

If you've any comments, questions, tips, please post=)
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Unread postAuthor: Just1ofgod » Wed Nov 28, 2012 7:18 pm

cool stuff what is the led running off is it hooked right to the battery or is the other electronics needed to make it work?
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Unread postAuthor: Technician1002 » Wed Nov 28, 2012 8:52 pm

If you get really good and gently curve the plexiglass either from sanding and polishing or heat shaping, you can change the virtual image distance of the dot to near your target distance instead of appearing way in front of the target just a few inches from the viewer. Put a sheet of plexiglass on a metal bowl in the oven and heat till it sags slightly. Experiment till you get the right curve.

Another option is to place a lens between the LED and the plexiglass to place it's virtual image near 25 yards. Either method works well. This latter method reduces parallax errors.

The current configuration provides large errors if the eye is not dead center just like using open sights without the rear sight. The two sights are only accurate when sighted in line with both.
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Unread postAuthor: D_Hall » Wed Nov 28, 2012 10:13 pm

To add to what Tech said... IIRC, the proper shape for the reflector/lens/whateveryouwannacallit is hyperbolic.
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Unread postAuthor: DasAbonnent » Thu Nov 29, 2012 8:21 am

Thanks for replies=)
yep, i know. But i don't think i can create such an good and even lense^^
yes, with a collimator lense it would work..like in my "real" red dot i'Ve got.. but hard to make by yourself..

The idea with the metal bowl is cool=) thanks, maybe i'll try sometime

@just1ofgod
Sure there's something needed! You can't hook up a 18V LED on a 9V battery;-)
1. there's a small switch on/off
2. there's a resistor between battery and LED
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Unread postAuthor: Technician1002 » Thu Nov 29, 2012 10:16 pm

Contrary to popular belief, you can hook an 18 volt LED to 9 volts. The bare LED (for red) has a forward voltage drop of about 1.8 volts. The series resistor is selected to drop the supply voltage to the LED at it's desired drive current. By using 9 volts instead of 18 volts, the voltage dropped on the resistor drops from about 16 volts to about 7 volts, so the current on the LED at the same 1.8 volts, would be about half. It will still light as there is still forward current, but just less then 1/2 as bright. Try it.

With Ohm's law, you can calculate the original voltage and current for the LED. Current = Voltage divided by Resistance. For example a 5,000 ohm resistor with ~16 volts would pass 0.0032 amps or 3.2 milliamps. With the current known, you can select a smaller value resistor to provide the same current and thus brightness with a 9 volt supply. In the above example, a resistor of about 2.2 K a standard value will be a close substitute for 9 volt operation.

LED's of other colors have different voltage requirements. Most white or blue LED's use about 3.6 volts. This is why many LED flashlights use 3 1.5 volt batteries. 3 volts is too low to light them. 4.5 volts will light them with a proper current limiting resistor.
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Unread postAuthor: Just1ofgod » Thu Nov 29, 2012 10:32 pm

thanks for the info guys maybe ill give it a shot and try to make one of these for my big bore bbmg project im working on
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Unread postAuthor: DasAbonnent » Fri Nov 30, 2012 7:57 am

THAT WAS FALSE! Sure 1,8Volts!! :D
not 18, but anyway i think everybody knows that=)
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Unread postAuthor: DasAbonnent » Sat Dec 29, 2012 4:49 am

ThiWhitaker
EXACTLY!=)
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Unread postAuthor: wyz2285 » Sat Dec 29, 2012 8:30 am

Cool stuff to add to some non ghetto yet non factory quality guns, definitely a lot cheaper than the red dots I bought, also adequate for pos-apocalyptic creations :wink:
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Unread postAuthor: DasAbonnent » Sat Dec 29, 2012 4:30 pm

haha xD sure;-)
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