Hello everyone,
I would like to narrow down my beam of an infrared. I read somewhere that you can with a sort of convex magnifying glass and create a tube, then put it all together. Has anyone had any experience with this?
Here is my scenario.
I don't want the IR beam to be wide. Possible X diameter within Y distance.
Is it possible to transmit the beam to at least 100ft? If yes, how can I achieve this?
Can I attach many IR transmitter in series to make them brighter? If yes, can they all pulse at the same time?
Sorry to list down my problems, but I thought it would be easier to follow than a whole paragraph.
The TV-B-Gone is a good high-power infrared transmitter reference design with multiple emitters. Adafruit sells a kit and you can see the driver circuits in the documentation there. Basically if you drive the IR emitter through a transistor you can max the transmitted power.
Lenses, tubes, and alignment will be critical to make best distance. One hundred feet is ambitious in daylight.
Hi there dc42,
Thank you for that information. I did some googling, but this is the first time I've heard of IR laser diode so I'm probably not getting the right information. Do you have any links to how it works and where I can buy them?
SeanD:
Hi there dc42,
Thank you for that information. I did some googling, but this is the first time I've heard of IR laser diode so I'm probably not getting the right information. Do you have any links to how it works and where I can buy them?
Lining up of optics is typically done using a visible red laser, bearing in mind that the refractive index of lenses etc. may be a little different at infrared wavelengths.
Hi there dc42,
It seems an IR laser diode may be too dangerous for my purpose. I am trying to build a very simple laser tag game for my kids. I have the game working, but only working from about 3 ft max. I am looking to see how I can extend the range long enough to play in the backyard at night. Do you have any thoughts on it?
Ah, I thought you were wanting to do some communications.
The first thing you need to do is select an IR emitter with a high radiant intensity per unit solid angle. Unfortunately, Radio Shack doesn't give the part number of the IR emitter you are currently using. However, it's probably one with a broad output angle, and what you need is one with a narrow angle. A quick search of one of my local distributors turned up http://uk.farnell.com/osram/sfh4550/led-ir-5mm-850nm/dp/1573495RL, which is a narrow-angle (3 degrees) device. My guess is that its radiant intensity (700mW/sr typical) is probably about ten times that of the device you are using, so you should get around three times the range.
Are you already running the IR diode at its maximum peak current (100mA)?
IIRC, IR needs a special type of lens to be focused - ordinary glass or plastic lenses may or may not work well.
That said - you need to be very careful with IR light (especially high-brightness LED or laser IR) - the human eye does not have a blink response to IR light, so any direct or indirect (ie - reflected) exposure can potentially cause harm.
That LED is rated at only 50mA maximum and the datasheet does not specify the radiance or half angle. So it is unlikely to be suitable for your application.
To switch a LED that needs more than the 40mA Arduino pin limit, use a transistor to switch the LED. See https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQiEBg44h_5hg9FqHss6SMdKKP7yU7FvG438oU4XvOGS_-sR80D. The transistor can be BC337 or similar, and R1 can be 1K. Calculate R2 to get the desired forward current through the LED, by subtracting the forward voltage of the LED from the power supply voltage, subtracting another 0.1V for the transistor, and then dividing by the desired forward current. For a 5V supply and 50mA forward current, it should work out to about 68 ohms.
cr0sh:
IIRC, IR needs a special type of lens to be focused - ordinary glass or plastic lenses may or may not work well.
I used to work with carbon dioxide lasers. At those wavelengths (around 10um), glass is opaque and we had to use other materials such as zinc selenide or sodium chloride. But at the near-IR wavelengths (less than 1um) produced by IR LEDs, glass is transparent.
The single thing you can do to most improve the range is to get an IR LED that produces a more focused beam. Browse the distributors sites, and look for an IR LED with high specific radiance (measured in mW/sr). The best one I found on Farnell is http://uk.farnell.com/osram/sfh4550/led-ir-5mm-850nm/dp/1573495.
