The Board of Education Rev B has servo headers (labeled X4 and X5), but it does not have a Servo Power Selection Jumper. On this board, the X4 and X5 headers are permanently connected to Vin. When connecting servos or other devices to the X4 and X5 headers, be sure to use a power supply that does not exceed the voltage tolerance of the servo or device. For example, the Parallax Continuous Rotation Servo requires a 6 V (maximum) supply, so it should not be plugged into the servo headers if using a 9 V battery or a 7.5 V or 9 V wall supply, or the life of the servo could be shortened. A 4 AA cell battery pack with a compatible barrel jack connector is available from Parallax (#700-00038).
To disable power on the Board of Education Rev B, you must disconnect the power supply or battery at its connector.
Most of the connections labeled Vdd are supplied by the Board of Education Rev B’s 5 V, 1 A voltage regulator. However, the socket labeled Vdd on the X1 AppMod header is instead supplied by the small voltage regulator on the BASIC Stamp module. The BASIC Stamp module’s voltage regulator only has a 50 mA current budget for its processor, certain circuits built on the breadboard and connected to I/O pins, and any devices drawing current from its Vdd pin. The socket labeled Vdd on the X1 AppMod header draws current from the BASIC Stamp module’s Vdd pin, so an AppMod or other device that draws current from this pin has to stay within the 50 mA current budget, which in many applications may turn out to be only a few milliamps. Before using an AppMod with the Board of Education Rev B, verify that it gets its power from the AppMod Header’s Vin socket, and not Vdd.