Carrier Boards

A carrier board is a board you plug your PIC into so that you can feed it the necessary power and have a convenient way of connecting the I/O pins to something useful.

My first general-purpose carrier board looked like this one.

As you can see, it's pretty basic. It consists of the following components:

• An 18-pin socket to plug the PIC into.
• A 4MHz crystal and two 22pf capacitors to form the oscillator.
• A 10K pull-up resistor for the master clear pin.
• A momentary push button to pull the master clear pin low, which will reset the PIC.
• A connector to plug the power supply into.
• A slide switch to turn the power on and off.
• A 1K resistor and LED to indicate that the power is on.
• A 220uf capacitor that acts as a power line filter.
• A 16 pin terminal block that are connected to the PIC's I/O pins.
• A .1uf capacitor between the +5V and ground pins of the PIC (not visible).

The 13 I/O pins, as well as +5V and ground are connected to the terminal block. One of the terminal block pins is unused. Many people include a voltage regulator on their carrier boards. I do not. All of my 5 volt power supplies are regulated, so I don't bother with the regulator.

Here is one of my newer carrier boards:

Probably the first thing you'll notice about this "one" is that it is actually in two pieces. The board on the left is the main board. The regular machine pin socket has been replaced with a ZIF (zero insertion force) socket, and just for the heck of it, I've also added a fuse. It's probably not necessary, but they're cheap, so why not? Instead of a terminal block, the board contains a 20 pin header. This allows me to use a ribbon cable like the one shown at the top of the picture to connect the main board to an accessory board like the board on the right.

This setup allows me to swap in different accessory boards without having to wire up all the parts on the main board for each custom accessory board I need to build. In this particular instance, each I/O pin is connected not only to a pin on the terminal block but also to two pins on the SIP socket strip right next to the terminal block. The SIP socket strip allows me to use a wire to connect an I/O pin bread-board-style to one of the 10K pull-up resistors or an LED that is at the top of the board. At the bottom left of the board are a pair of optoisolators with a SIP socket on the transistor side of the opto so that I can connect an I/O pin to it just like the pull-up resistors at the top.

The key to success with the two-board setup is making sure that the 20 pin header is wired the same on every board so that everything is completely interchangeable.

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Page last modified on 03/13/2004