🚀 go-pugleaf

In article <pschleck.702924799@odin> pschleck@odin.unomaha.edu (Paul W Schleck KD3FU) writes:
>I was wandering through Walgreen's drug the other day, and saw an
>interesting Easter toy selling for a couple of bucks.  It's a
>fuzzy chick that chirps when you hold it in the palm of your hand.
>The woman behind the register was kind enough to demonstrate it for
>me.  Touching two metal grommets on the bottom of the thing started
>it chirping.
>
>Since skin has a very high impedance (i.e. when you touch two
>probes of a multimeter to your hand, you don't get a measurable
>amount of resistance/load), it probably detects the very slight
>difference between an infinite resistance/impedance, and the very high 
>impedance of skin (warm, oily/sweaty skin works better than cold/dry
>skin, fingertips work better than the palm of your hand, etc., etc.).
>
>Shorting the contacts with metal like copper produces unpredictable
>results (fast, irregular chirping, or no chirping at all) probably
>due to it being sensitive to too much load.
>
>I only have one of them right now (and it is already reserved as
>a present), but when I get some more (hey, if you can get over
>the embarrassment of buying SOME things at a drugstore, you can
>buy ANYTHING :-), I'll sacrifice one to science and report on its
>"guts".  It uses a standard watch battery and might be an interesting/
>educational present for the little tykes.

I have one of these that my dog did the honors of exposing the 'guts' for me.
There is some sort of custom hybrid on the circuit board covered with a gob
of epoxy.  The trigger is a single transistor with a 1 Meg resistor connected
between V+ and the collector and the input to the blob of epoxy.  The two 
metal contacts attach to the base and emitter.  Looks like one of them is 
simply grounded.  Let's see if I can show it in ascii-draw:


	_________
      /          \
      |  epoxy   +---------+---------+
s ----+   blob   |         |       +++++
p ----+          |         /       -----
e     |          |    1Meg \         |
a     |          +---------+         |
k     |          |         |         |
e     \-------+--/        /          |
r	      |          |           |
	      |     0----|           |
	      |           \          |
	      |     0------+---------+
	      |            |
 	      +------------+

-- 
John E. Greene             Everyone needs something to believe in.  I believe 
Sr. Staff Engineer         I'll have another homebrew!
Desktalk Systems Inc.      
(213) 323-5998             internet:  jeg@desktalk.desktalk.com