IR Emitter/Receiver Suggestions for Outdoor Usage

[nafix]

Can anyone offer some suggestions on IR emitter/receiver combo ICs that will work well outdoors in the sunlight? I will need to detect about a range of 2 feet to be safe. The goal is to detect a basketball going through a hoop. So the idea would be for the emitted signal to bounce off the ball and back to the detector. From some searching around it appears a modulated IR signal is the way to go to avoid interference from other sources. So I'm hoping to find a product that has both an emitter and a receiver on board that use a modulated frequency.
Any comments on a white basketball net reflecting the emitter signal?

Also, I've looked into using a color sensor that they sell on sparkfun (Avago ADJD-S311-CR999). I'm fairly sure the sun will emit the orange color frequency and cause some issues. Although this could be worked around because the sensor has gain associated with the color frequency. So sensing more orange gain than normal could be a detection of a basketball. The real problem is that I don't think it will be reliable for a range more than a couple inches because the white light emitter on the thing doesn't appear to be very strong (I couldn't verify this). Any thoughts on this as well?

Thanks!

 

[KeepItSimpleStupid]

Why bounce off the ball and hit the detector?

Conventionally, you set up a receiver/detector pair that's always on and detect the interruption of the beam.

Now, you can place an artificial reflector at the end of the beam too which is another way of doing it, but your still in this case looking for an interruption of a steady signal.

 

[nafix]

Yes, that is an option, but one that I am avoiding. I should have stated before that I didn't want to explore this option because of having to run wires around the basketball rim to set up the receiver or detector. I would like a single unit that can be placed under the rim where it connects to the back board.

 

[jpanhalt]

I have not seen any slow-motion video of when a basket ball goes around the rim but not through it. Will that be a problem? I guess, if the reflection is from a few inches below the hoop the rimming will not be a problem.

Almost any emitter will work with a Vishay TSOPxxxx detector. You could put the pair just a little below the loop on the backboard. 38 KHz is a common frequency. Do you want to use discrete components, like the NE555, or would you prefer a simple microcontroller, like the PIC 12F5xx series?

John

 

[nafix]

The ball rimming out could be an issue, but it shouldn't happen often enough to be a major issue. Like you said, maybe I could offset the detector/emitter a few inches below the rim. I'm going to be using a PIC24 most likely. So, pull up resistor to i/o port connected to emitter led, and then toggle the output port at 38 KHz? I'd like an emitter that has higher intensity than the standard emitter.

 

[jpanhalt]

I'm going to be using a PIC24 most likely.

Well, you are ahead of me there. I am still trying to get comfortable with 16F's.

So, pull up resistor to i/o port connected to emitter led, and then toggle the output port at 38 KHz? I'd like an emitter that has higher intensity than the standard emitter.

Sounds good to me. Your emitter is current driven. So, you will need a small transistor or logic mosfet to drive it from the PIC. What do you mean "standard emitter?" I have used a 200 mA emitter at a foot or two in a reflection mode. Situated below the rim, distance should not be a problem. Worse comes to worse, just parallel the emitters.

John

 

[nafix]

I have a basic emitter/detector pair from Sparkfun that I used previously. The emitter was very weak on that (40 mA or something), I guess I assumed that was a "standard" emitter. This pair didn't use modulated frequency and was a tad sensitive to indoor ambient lighting. Thanks for your help. Can you recommend an emitter like the one you referenced in your post?

 

[jpanhalt]

I think I used the Optek 130 that I got surplus from Electronic Goldmine, but it may have been the generic one from Radio Shack. That was more than 10 years ago, and the emitter is not critical, so long as the wavelength matches the receiver. Your duty cycle is going t be ≤50%, so you can push the rated continuous current. Like I suggested, if you need more power, just put them in parallel. You may want each to have its own current limiting resistor.

John

 

[nafix]

Cool. Btw, I'm a little confused about the 38kHz. This only means that the IR wavelength will be emitted (flashed) at a rate of 38 kHz, right?

 

[ronsimpson]

Yes, flashing.
Room light is D.C. (on all the time).
Florescent light pulse at 120hz.
Sun light is broad band.
If you transmit at 38khz and build a narrow band receiver it will block out the off band light.
If you only remove any signal below 10khz you will get rid of most of the noise.

 

[jpanhalt]

Check the datasheet for the TSOP 32138 (https://pdf1.alldatasheet.com/datasheet-pdf/view/252290/VISHAY/TSOP32138.html). The 38 KHz (or whatever frequency you chose) is the pulse frequency. The receiver filter needs a period of pulses followed by a period of silence to recognize the signal. Tuning is quite broad, as sunlight and fluorescent lights are the major sources of interference, and they certainly don't pulse at 38 KHz.

There are many different receivers on the market. You will need to pick one that you can source easily. By and large, they are quite similar, bit there are some varieties designed for different purposes. So, when you select one, be sure to check the datasheet.

John

 

[KeepItSimpleStupid]

With a metal reflector at the other end you still can use an interrupting system with the emitter and detector at one end.

 

[jpanhalt]

I just thought of another confounder. If you use reflection, then when a player swipes the net from under the rim, it may give you a false positive.

John

 

[ericgibbs]

Cool. Btw, I'm a little confused about the 38kHz. This only means that the IR wavelength will be emitted (flashed) at a rate of 38 kHz, right?

hi,
As John has suggested a pulsed IR system would work for you.
This link should help.

https://www.electro-tech-online.com/blogs/ericgibbs/196-tsop1738-when-used-beam-break-detector.html

 

[nafix]

Assuming the basketball takes no more than 100 or 200 ms to fall past the sensor, do you think this will be enough time for the detector the see bounce back from the emitter off the basketball? It seems like it would since 38k Hz would flash once every 1/38k s (~0.02 ms).

 

[jpanhalt]

The simple answer is yes.

Here is a much better link to the datasheet for the example I gave above: https://www.electro-tech-online.com/custompdfs/2012/07/tsop341.pdf

Note the timing requirements, particularly Figures 1 and 3. If the 38 KHz beam is modulated at 833 Hz (i.e., period is 1200 uS as shown), it can track that modulation. A 12" ball going roughly 570 mph takes 1.2 mS to pass a point.

John

 

[nafix]

Hi John, I have another question for you. I'm getting ready to purchase a batch of the Vishay IR detectors off Digikey. In the datasheet you linked to previously, there was a table with the various detectors under three categories: Short burst and high data, noisy environments and short burst, very noisy environments and short bursts. Do you think I need to go with a detector made for noisy environments since this will be subject to sunlight? What is the tradeoff for the "noisy environment" detectors, the time it takes to detect pulsing? If that's the case, I would think I should go with a detector made for very noisy environments, since I only need to detect a single transition of bit logic in a comparatively large time window.

 

[jpanhalt]

I used an earlier generation of detector that did not distinguish on the basis of the AGC (automatic gain control). Sunlight is a high background, but is not particularly noisy as in being variable. You are not high data rate. Thus, I would go with the noisy or very noisy. Maybe get two of each. I would start with the noisy one. If no problems, then plug in the very noisy one and see if range is adequate.

John

 

[nafix]

Thanks John! That's probably what I'll end up doing (buying 2 of each). I found a Vishnay emitter that draws 250 mA current, and has a half angle power of 5 degrees. I looked for an emitter with a lower half angle power so that its not emitting too much IR light except for directly in front of it. I am concerned that the white net might reflect back enough IR to trigger the detector. If this turns out to be the case, I'll probably have to move on to a color sensor.

 

[languer]

Just re-iterating what Eric mentioned; some examples are found in the following two links:
> https://www.electro-tech-online.com/blogs/languer/156-ir-beam-break-test-bed.html
> https://www.electro-tech-online.com/blogs/ericgibbs/196-tsop1738-when-used-beam-break-detector.html