Why not have the toy car, or servo or whatever just release a latch and let
spring tension or gravity slam the door shut?

Bob Ammerman
RAm Systems

----- Original Message -----
From: "Lawrence Lile" <llile@TOASTMASTER.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, June 24, 2002 1:27 PM
Subject: [EE]: Hummingbird trap


> A friend of mine is a biologist, a professional ornithologist.  (My cat is
> also an ornothologist, an avocation I have tried to stop for quite a while
> as she leaves them on the front porch).  He studies hummingbirds, and is
> looking to make a trap for them.
>
> He has a little hummingbird feeder built into a special cage with a
trapdoor
> for catching hummingbirds.  Now he doesn't just want to catch any
> hummingbird, he wants to watch the cage, and when a specific hummingbird
> comes to feed, he wants to actuate the trapdoor remotely and catch them.
I
> think he bands thier legs, weighs them, takes blood samples, eats them for
> lunch, I don't know.  How he tells them apart who knows ( maybe he asks
for
> a picture ID ).  I guess he is looking for rare, unbanded, or birds of a
> particular gender and so on.
>
> He has several traps all used at the same time, so another part of the
> challenge is to have several traps on different frequencies or signals so
> each trap can be fired individually.
>
> He has tried to make a badly hacked system that is cobbled out of a model
RC
> car which hasn't really worked yet.  He punches the button on the RC car
> control, and a wheel turns on the toy truck held to the bottom of the cage
> by a bunch of rubber bands, unwinding a string which holds up the
trapdoor.
> There is probably a midget captain, a candle burning through a piece of
> string, a rolling bowling ball and a rabbit in the contraption somewhere,
as
> well.  The toy car only has reverse and forward modes, no stop, so it
winds
> the string into a knot at the end of a trap cycle.
>
> The big  problem is, hummingbirds are fast.   His toy car can lower the
> trapdoor in several seconds, and by then the wary hummingbird is long
gone.
>
> What he'd like is a radio controlled remote system that releases the
> trapdoor instantly.  He's also like it to be cheap to build and not
require
> too much expertise to construct.  The challenge is probably to hack this
out
> of some commercial product or other with a couple of extra parts and not
> much programming.  A little soldering is OK.  A few extra solenoids would
> not be a problem.
>
> It is easy to think of a way to do this with fancy microcontrollers  and
> such.  Keeping it simple is a little harder.
>
> How about RC model airplane controls and servos?  I have messed around
with
> servos driving them directly with PICs, but never messed around with the
RC
> controls that are really meant to run them.  Could a simple-to-build
system
> be built with this stuff, and at what kind of cost?  Could a servo be
> arranged to drop a trapdoor fast?  How fast can a servo operate, is well
> under a second from stop-to-stop achievable in a small servo?
>
> --Lawrence
>
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