Hi all.

I have just completed a "prototype" project (hobby), that is an 
Infra-Red remote control for a Nikon D70s camera. The primary motivation 
is to create an "extended range" relative to the remote that Nikon sells 
(I set the camera on a tripod, focussed on a bird feeder. I want to be 
really far away and still trigger the camera... maybe even set up a 
motion detector ... ;-).

Right now it is working, but it's range is "only on par" with the Nikon 
remote (and a lot more clunky ;-).

I have a bunch of IR LED's available. They are 100ma with 1V volt drop. 
They have a 20deg "half-intensity" beam angle. I am using 2 AAA cells to 
power the system (nominal 3V).
Because the IR Signal is a 40KHz 50% duty cycle when on, and for each 
"trigger" it will only be on (at 40KHz) for 8ms for the complete trigger 
sequence of 85ms, I believe I could exceed the 100mA "continuous" 
rating. It's "pulse" rating is something like 10A for a few uSec.

I am using a 16F628A with INTOSC@4MHz

To Drain the current of 100mA, I am using 4 PORTB pins as a sink (25mA 
current per pin as per datasheet). My calculations indicate that to get 
100ma through the LED with 1V forward, and 3V system, I need 20Ohm 
resistance. To sink that through 4 pins, I connected an 82 Ohm resistor 
to each pin, and then the LED through the 4 parallel resistors, giving a 
net parallel resistance of about 20Ohm.

Now, for my questions.....

1.) How do I get better range on the IR remote?

Options I have considered....:
   i) Drive the IR-LED at more than 100mA (add another PORTB Pin to sink 
current to?) If so, how High can I go?
  ii) Add another IR-LED (either in parallel with first? or as a 
seperate system entirely?)
 iii) Get a "brighter" IR-LED?
 iv) Add another AAA cell, run the system at 4.5V?
  v) Get a "narrower beam" IR-LED.

Which avenue holds the most promise? Is there an option I have not 
considered?

2) What is the math for 2 LED's in parallel....? To get 100mA through 
each LED I'd need to sink 200mA. Probaby use an external transistor for 
that.... not PIC Pins. Would it be better to use 2x20 Ohm resistance one 
for each LED, or could I use a single 10 Ohm resistance common to both 
LED's?

3) Why does it not work well at "close range" < 6inches or so from 
Camera. Is it possible to "flood" an IR receiver?

I know that I have given a lot of detail. Hopefully someone with more 
experience than me at "real-world" electronics can bring their 
experience to bear on my challenge... ;-)

Thanks in advance.

Rolf
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