Wednesday, April 4, 2012
Silly pointless stuff... (Mr Jiggles)
I like to think of crystals as highly ordered structures that deform a bit in the right kind of electric field - remove the field and they go back to their original state and in the process create a tiny electric field of their own. Now depending on how the little crystal is cut, what it's composed of, how it's treated it will have at least one frequency at which it likes to oscillate.
The other thing we need to consider is how we will make the little amount of energy useful - we need to make it bigger. It happens that our little friend (the npn bjt) does a great job of taking a tiny current and making it bigger.
I know I'm going to link the crystal to the base (to control a bigger current collector to emitter) and I know we need a voltage to load the crystal (but not a lot) so let's start with a 220k resistor to pull the base high from the collector.
Ahhhh... silly mistake. If you look back at the sketch I connected the crystal directly to the base (and this isn't going to leave any room for the jiggling to happen unimpaired - like trying to dance in a car - not going to be beautiful).
Enough for today... think about it and we'll see next time.,.