Copyright © Parallax Inc.

Board of Education Rev C (#28150)

v2.0 5/14/2010 Page 5 of 5

Notes for Earlier Board Revisions

Board of Education - Serial Rev A Special Instructions

Servo Ports - There Are None!

The Board of Education Rev A does not have servo ports. However, 3-pin connections for servos and

other devices can be built on the breadboard. For an example of connecting a standard servo to the

Board of Education Rev A, see the instructions in the Servo Circuit Connections for Older Boards pdf at

Servo, with a 6-volt power supply via a breadboard circuit, Parallax carries 4 AA cell battery holder with

tinned leads (#753-00001) for this purpose.

3-Position Switch - There Isn’t One!

To disable power on the Board of Education Rev A, you must disconnect the power supply or battery at

its connector.

Board of Education - Serial Rev B Special Instructions

Servo Ports - There is no Servo Power Selection Jumper!

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).

3-Position Switch - There Isn’t One!

To disable power on the Board of Education Rev B, you must disconnect the power supply or battery at

its connector.

Vdd on AppMod Header - Limited Current Budget

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.