School Board Information
An Assembled School Board:
Major Features
- Professional-quality double-sided printed circuit board
- Complete 5-volt, 1 Amp power supply (reverse-voltage protected)
- Innovative "breadboard-straddling" design allows for separating input and output circuitry
- Input voltage can be routed to breadboard, allowing for ADC voltage measurements for battery supplies
- Completely self-contained; serves as a bug-free and reliable platform for project development
- Provides an inexpensive, safe and flexible solution for classroom applications
Breadboard-Straddling
The easiest way to set up the School Board for breadboard use is to connect two 400 tie-point breadboards as shown below. Notice that the School Board silk-screen labels identify the 20M I/O pin connections; the tilde symbol ("~") identifies which inputs are also ADC inputs, and "IR" identifies the input and output pins that can be used with the 20M's IR commands (see Part II of the PICAXE manual for details). Also note the small amount of space between the breadboards. For some reason, when two breadboards are directly attached to each other the row spacing between them is not an exact multiple of 0.1 inches (IMHO, it should be)!
If you would like even more flexibility in circuitry layout, take a third 400 tie-point breadboard, remove the power rails and cut the main section in half along its center-line. Attach one half to each side of the School Board as shown in the following photo. This arrangement allows for additional flexibility in wiring your projects because connections can be routed to the left or right of the breadboards without using up space in the main breadboard area.
Accessing the Input Voltage
The 3-pin male header located between the two electrolytic capacitors and labeled "Vcc Out" (see top photo on this page) is used to enable access to the input voltage if desired. For example, if your project is battery-powered you can place the 2-pin shunt in the "ON" position and access the real-time battery voltage level (less the drop across the 1N4001 diode) at either of the Vcc pins on the edges of the School Board. By setting up an appropriate voltage divider, you can monitor the real-time Vcc voltage level via any ADC input pin. Warning: if you aren't certain of how do do this, it is best to leave the "Vcc Out" shunt in the "OFF" position. Applying more than 5 volts to any PICAXE pin can damage or destroy the pin, and possibly the PICAXE processor as well!
A second reason to access Vcc on the breadboard would be whenever you have peripheral circuitry that requires voltage levels greater than 5 volts in order to operate. Whenever you enable Vcc access, it is most important to route it carefully on the breadboard. Failure to do so may result in damage or destruction of mis-wired components!
One Final Note
The two 2-pin headers located next to the 5x2 header and the power connector (see the top photo on this page) are not connected to any circuitry on the School Board; their only function is to physically support the end of the board. Therefore, it's OK to use that area of the breadboards for your I/O circuitry.