Been a busy month - New transmitter, 660nm

It has been a busy month, of building.  Earlier this year I designed a new MCW transmitter using the ATTiny45 microcontroller.
The code has two modes; a beacon mode of three different tones and a solid tone for sending MCW.  I use a hardware interrupt, a switch, to flip between modes.  I used a closed circuit 3.5mm jack for the key.  When it's plugged in the LED is powered off until the key is pressed.  When it's unplugged the power is connected to the LED.

I'll post the code and a schematic of my circuit in a future post.  For now here are some pictures.

This is the inside of the transmitter.  The circuit is built on veroboard, in the center of the picture is the ATTiny45 chip.  Next to pin 5 is the 2N7000 transistor that I use for switching the LED.  Also visible is the voltage regulator, the hardware interrupt switch (red one in the center), and the back of the LED (bottom center).  The transmitter runs off of a 9v battery that fits into a holder in the case.

Here is the top view of the finished transmitter.  If the case looks like a garage door opener, well that's because that is exactly what it is.  I picked it up at AxMan surplus in Minneapolis.  The LED, a Micro Electronics MSB90TA-5, is visible at the bottom of the picture.  It's a 10mm ultra high brightness LED (Radio Shack calls them Jumbo-Super Bright Red LED #276-0086).  It's a pretty cool LED for a test transmitter, has about a 6 degree 1/2 angle, and can run at 200mA with a 10% duty cycle.
I am running it at 50% duty cycle at around 90mA.  It's rated at a luminosity of 10000 mcd at 20mA.   At 90mA (50% duty cycle) the data sheet has it's output at 25000 mcd.  Wikipedia has a good write up on Candela, the measurement of luminous intensity.
In the middle of the case from left to right.  3.5mm key jack, toggle switch for mode selection, on-off switch.

Here is a short video of the transmitter in action.  The transmitter is aimed at my G3XBM receiver. The link will take you to his site and the schematic.  It's a simple design and works extremely well.  I used this receiver, with a couple of modifications, for my initial beacon tests which included some cloud scatter.  Results were very exciting.

Next thing to do is set this up outside and see how far away I can hear it.  I don't plan on putting a lens in front of the LED.  With a 1/2 angle of 6 degrees, it should be good for short range communication.  I'll post my results as soon as my tests are complete.

73,

Warren