Finally completed the "final" version of a working Light system

The other thing that has been keeping me busy outside of;
working on my 10GHz system, preparing for the Golf Channel AmTour's National championships, playing with my granddaughter and new grandson, and working to pay for all of this,
was fiddling with my light system, namely the housing for the receiver and transmitter.

This is what I came up with.

Front view

Transmitter, on the left, uses 12 SFH4550 IR Led's.  It also uses my 555 timer PWM modulator with an LM833 microphone amplifier.  I eliminated the filtering in the audio amplifier to simplify it as I found that it wasn't necessary.
The receiver is using a 90mm diameter fresnel lens with a 50mm focal point that I found on EBay, I've also seen them on Amazon.  These dimensions are almost perfect for the BPW34 IR detector.  The receiver is the KA7OEI v3.10 on a circuit board designed by K7RJ.
The housing for the transmitter and receiver are designed by me and are 3D printed.  More on that below.

View from behind

As transmitter uses 12 led's wired in 2 parallel sets of 6.  The box contains the circuit boards and the jacks on the back are, from left to right, microphone input, microphone gain, and power.  I've separated power for the mic amp (9V) from the pwm modulator (12V).  I am supplying 425mA to the led's driving them at a 20% duty cycle and I was afraid that I might get noise from the modulator into the amplifier.

First contact was made with Donn, WA2VOI a couple of weeks ago after Tuesday night coffee with the Northern Lights Radio Society at Nokomis Beach Coffee near Lake Nokomis in Minneapolis.
We worked out the narrow beamwidth and then made our contact.  After that we played around a bit bouncing our signals off of parked cars, houses, and piles of snow.  I logged the contact in Log Book of the World.  Just for information, it will take frequencies at lightwaves, I entered it as 3.52e+08 and LOTW resolved it.

3D Printing
I have uploaded my transmitter and receiver designs to Thingiverse.com.  I am making them free to anyone who wants them.
The Transmitter is at: http://www.thingiverse.com/thing:2751923
The Receiver is at: http://www.thingiverse.com/thing:2765972

Each of these prints used less than $1.50 in filament to print.
There are probably improvements that I could make to each of these.  If I develop any into a working example, I will post them here.  If you create any improvements please let me know.

What do Baseball and IR Optical communication have in common?

Seems like a strange question to ask, to start a blog post.
But like they say, a picture is worth a thousand words.

Front view of the IR PWM "Cube" transmitter

So to answer that question...
They share a storage container.
Here is the first iteration of my IR PWM Optical transmitter.  The case is a cube that is used to store a signed baseball.  It measures 3 1/8" per side.  This transmitter uses the same LEDs as my beacon, the Osram SFH4550 IR emitter.  I have them in metal LED holders that I picked up from Radio Shack.

I use a standard 555 timer chip to generate the PWM.  The duty cycle is 22% at a frequency of approximately 70Khz.  Below is the schematic of the transmitter.

555 timer PWM circuit

Pin 5 is used as the input from the audio amplifier.  The audio modulates the duty cycle and not the PWM frequency so my original receiver circuit is able to demodulate the audio. The 555 timer is running in the astable mode.  D1 is a 1N914 switching diode and it's placement between the discharge pin and the trigger pin changes the charging of the capacitor to allow a less than 50% duty cycle.
I wanted a duty cycle of approximately 20% so I could feed 400ma through the LEDs. According to the data sheet that gives a good balance for improved radiant intensity and current draw.

Back of the IR PWM "Cube" transmitter

The back of the transmitter has the jack for the audio source, either a electret microphone or from a laptop sound card for digital modes (upper left).  The knob is connected to a potentiometer that controls the gain of the audio amplifier.  The jack in the lower right is for DC power.  For this version of the transmitter I'm using 6 - AA rechargeable batteries with an output of 7.5 volts.

First version of audio amplifier

This is the schematic of the first version of the audio amplifier that I built.  I liked the way it sounded however I felt that the parts count was too high and the three pole low pass filter was a little over kill, so I simplified it in the final version.

Vero board layout of the PWM and audio circuits

Here is the layout of the boards.  I put the audio amplifier and the PWM/switching circuits on separate boards.  I felt that would give me some isolation of the 70Khz switching noise and the audio amplification.  In testing I haven't noticed any switching artifacts from the transmitter.

I haven't completed any distance testing.  I have bounced the light off of the neighbors garage on one side and the trees in the other neighbors yard, but living in the city the distance is pretty small.
This will be something for another day.