Re: ATM Circuit Diagram for a Parks controller

["Bob May" <bobmay@nethere.com>]

I don't know the unit but if it is a 12V in device, it is probably a version
of the 555 powered inverter, the one with the big heavy transformer, that is
available in circuit form on the web.  There may be either 1 555 IC in the
unit, driving a square wave out or the circuit may be the dual 555 design
with a modified sine wave (power is on about 70% of the time) type.
Basicallly, if there is only one 555 then that is what is controlling the
frequency and is just driving the output transistors and if there is a 556
or two 555 ICs then one is generating a 120Hz and the other is pulsing when
the first is fired, producing a shorter pulse which is directed to one
transistor or the other.  The transformer is usually a 12V output
transformer running the other way with the 120V as the output.
Hope this helps.  The circuitry isn't complex inside of those controllers so
it shouldn't take very long to figure it out.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net