I figured out the coding scheme and programmed an ATMEGA32 to send out the
control signals from a output compare port (I used one of the timers to generate
40khz pulse streams). That was easy. Now I have this ugly breadboarded
microcontroller circuit double sticky taped to robosapien's back.
My plan is to make a RoboSapien backpack and shades...the backpack would house
the mega32, some small batteries and whatever else, and the shades would have an
ir led to blast directly into Robosapien's brain. I will probably include a
~40khz IR demodulater 3 pin device (they are about a buck) so the mega32 can
recieve commands and filter them to the robosapien via the shades. In this
fashion, two robosapiens could be made to fight each other...to the pain, of
My goal is to "hack" the robosapien without ever taking him apart. I don't
think you can improve on the analog/digital control scheme that Mark devised.
Hooking something like an electronic compass or ir range finders up to the atmel
mega32 and letting it tell robosapien where to move seems like the way to go.
Oh, one more thing...if you want to control robosapien using an ir led, you
really need to blast the IR....no little 20mA from a microcontroller port pin is
going to do much beyond a few inches. I built a little circuit using a simple
2n2222 npn transistor as a switch: emitter to ground, base to the atmel port
pin with a 1k base current limiting resistor in series, collector to the cathode
of the ir led, anode of the ir led to a 10ohm resistor connected to a 5V supply.
I put a 1000uF cap across the 5V supply. The IR led I am using is rated for
100mA max current at DC, and I am pumping about 350mA through it when it pulses.
Seems to control robosapien from at least 40 feet if he is facing it, and at
least 20 feet or so if it reflects off a wall he is facing. If you want to have
the ir trasmitter part a long way from the microcontroller (mine is about 15
feet away) put the transistor, led, resistors and cap on a small circuit board
and you can run the 5V, ground and pulse line over really small cable (I am
using some scrap cat5). This way the led has a local source of power in the
cap, and voltage drop over the cable is not an issue. I think the 2n2222 is
rated for 800mA or so? You could probably get away with 2 (or even 3) leds in
parallel, each with its own 10 ohm resistor from anode to 5V and all the
cathodes connected together to the 2n2222 collector. Oh, I guess at some point
you should remember that you will need more base current into the 2n2222, so you
should decrease the base series resistor to 470ohms or so.
Sounds like the makings of a cool "Servo" article. If nothing else, put up a
page when you get it finished!
Hmmm. You gonna put "toe sensors" or any other aux sensors into the backpack. A
periscoping sensor array perhaps?
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