Quote:
Originally Posted by TechShop
Perfect! Any time you can source your parts from the scrap pile, or the donor equipment, you're way ahead. I recall seeing similar boards in the 230v/50Hz split units I dealt with overseas. The window units I've played with here in the US were all running on simple capillary-bulb close-on-rise mechanical switches.
I'm mentally breaking down that board: Transformer to bring down the mains voltage... four discrete diodes are the rectifier... Perhaps the TO-220 package to the upper left is the LM7805 with a few filter caps surrounding it for 5v power. I imagine that little DIP 16 sized IC in the upper right quadrant of the first picture is some kind of gate array or buffer to interface the relays with TTL signals... or perhaps some other low complexity IC? The white header at the top is the control interface. ...and some kind of piezoelectric alarm/horn in there too? I would presume the large black square relay is the compressor. The 3 blue relays are fan motors, etc.
Good stuff.
|
You pretty much nailed the board. The mains transformer spits out 9vac or so which filters to unregulated 12vdc for the relay coils. The chip is typically a ULNxxxx (EDIT: xxxx=2003 or 2803) logic inverter which runs off the 7805 and makes or breaks ground to the relays and buzzer. The chip takes TTL inputs from the control at the other end of the white plug. Power and cold ground feed out the white plug to run the control at the other end. Love and happiness for my demands!
Another power board mentioned is the Amana p/n 30132033. This one has no mains transformer, but has extra high-current relays (original purpose:strip heaters) and thermistors on board that connect to the same type of pin headers. This board originally went in hotel PTAC units and still sells for around $20.
