connectorpcb-designschematicssymbol [~]
I'm working on a PCB design homework in PADS and I've come across a symbol that I have never seen (circled in red below). It is of a filled in rectangle with a triangle below it. I'm thinking it might be a type of switch but I'm not sure.
What is this symbol?
If I'm looking at the correct symbol, that's a feed through capacitor.
They are common on RF devices where they allow wires to enter a shielded enclosure.
Looking at the picture from the link you gave here they are:
That's called a potentiometer, or "pot" for short.
It is a fixed resistor between the two ends shown top and bottom in your schematic. The third terminal, shown with a arrow in a standard schematic symbol, is a wiper that contacts the resistive strip in a place that depends on how the pot is adjusted.
The net result is a fixed resistor end to end with a variable tap someplace within that resistance.
One use of these things is to make a variable voltage divider. Feed the fixed voltage into one end, ground to the other, and a variable voltage comes out the tap depending on how the pot is set.
This is also the basis for most old volume knobs. One wrinkle with adjusting volume is that humans perceive volume logarithmically. There are special pots called "log taper" where the resistance along the fixed resistor varies logarithmically, not linearly. If a pot isn't specified to have log taper, then you can assume it has linear taper. Log taper pots are harder to find now that volume controls are generally implemented digitially.
In your schematic, the pot is used as a rheostat. That's a 2-terminal variable resistor. That's what you get when you short the wiper to one of the ends, or leave one of the ends open.
Best Answer
That is a receptacle for a barrel connector. The symbol is supposed to imply circuit functionality. The following is not a standard symbol (don't use it!), but it should demonstrate the connection:
When you insert the connector into the receptacle, the center of the connector contacts the wide pin (the rectangle). The body of the barrel pushes the bent piece of metal out of the way, which remains in contact with the barrel because of spring tension.
In addition, when the barrel is inserted it also breaks the connection between pins 1 and 2. This can be used to detect if the barrel is inserted.