Prototype Switches

DIP switches can be used to select between 0 and 5 volts on circuit boards. However, for prototyping, their small size makes them inconvenient. For that reason, we have created prototype switches which are in the lab and work exactly like DIP switches, although they are bigger so they're easier to manipulate by hand. Since the switch does not have any power or ground connectors this must be done externally.

In the picture below, the DIP switch is on the right and the prototype switch is on the left.

• When the switch is turned on (in the "closed" position) it means that the connection between the top and bottom is connected and the input signal will pass to the other side (output).
• When the switch is turned off (in the "open" position) there is no signal and the output may float from 0 volts to 5 volts, and anything in between.

If we want a high (5V) when then switch is turned on, each input pin we are using must be connected to power. When the switch is off we want a low (0V); but remember when the switch is off it is in a floating state. To resolve our floating pins issue we need to add a resistor to the output pins.

Here's an active high configuration. When a switch is closed, the signal will be connected to power. When a switch is open, the signal will be connected to ground through the resistor.

Note the signal comes from the same side of the switch as the resistor. I've shown all four switches connected.

Here's an active low configuration. When a switch is closed, the signal will be connected to ground. When a switch is open, the signal will be connected to power through the resistor.

Note the signal comes from the same side of the switch as the resistor. I've shown all four switches connected.