Handy Board Assembly Tips

This page contains general hints for assembling the Handy Board. Some previous experience building and solder electronic components is assumed; for an introduction to soldering and how to mount electronic components, see Chapter 1 of the 6.270 Robot Builder's Guide.

Component Side versus Solder Side

The component side of the Handy Board is clearly marked COMPONENT SIDE, near the location where the piezo speaker is installed. The component side has the silkscreen legend printed on it---the white labels that indicate where the components are placed.

All components sit on the component side, with their leads poking through to the solder side. The board is then soldered from the solder side.

Don't get it backward because the board won't work, unless it is transported to a parallel universe.

The Square Pad Convention

On the Handy Board, square pads are used when a component is polarized and hence must be installed in a particular orientation. The square pad may have one of two meanings:

Negative Terminal. This applies to capacitors, LEDs, and diodes.
Pin 1. This applies to integrated circuits and resistor packs.

Following is information on the specific components that are polarized:

LEDs. Install so that the cathode (negative terminal) goes into the square pad. The square pad is underneath the white, shaded half of the LED placement silkscreen legend. On the LED itself, the cathode is indicated as the shorter of the two leads.

The above diagram shows a side view of an LED and the part silkscreen legend. The shorter lead of the LED is the cathode, which goes in the square hole.
Diode. Install so that the cathode goes into the square pad.

The cathode is marked with a band nearer to the cathode end (see above diagram).
Capacitors. If the capacitor is polarized (e.g., electrolytics and tantalum), either the + or - terminal will be marked. That is, there may be a + marking indicating the + terminal, or a - marking indicating the - terminal. Figure out which is the - terminal and stick it in the square pad.
If a capacitor is non-polarized (e.g., any value 0.1 uF or less), don't worry if the board has a square pad and a round pad. It doesn't matter how the capacitor is installed.
Integrated circuits. The square pad is pin 1. It's a nice idea to mount sockets so that its notch indicates where the notch on the chip goes. After soldering everything down it is significantly harder to see where the square pads are.

The above diagram shows how to count pins on a DIP (dual in-line package). Find the notch, and then pin 1 is in the lower left corner beneath it. The pin numbering proceeds counter-clockwise from pin 1.
DIP sockets have a notch like the notch seen on the chips themselves.
Resistor packs. Most of these are polarized. The banded end is pin 1, which goes in the square hole.

The above diagram shows two sample 8--pin resistor packs. The left-hand pack has the ``band style'' marking; the right-hand pack has the ``dot style'' marking. In either case, the marking indicates pin one of the resistor pack, which goes in the square hole.

The 6811

PCB Mounting

There is no square pad indicating pin 1 on the 6811. The 6811 is mounted in a PLCC (plastic leaded chip carrier) socket. The socket is soldered down to the board, and the 6811 is inserted into the socket.

The above diagram shows the 6811 socket, with its chamfered (or truncated) corner in the upper left. The 6811 itself has a matching chamfer in its upper left corner (the 6811's pin 1 is indicated with a dot).

It is imperative to install the PLCC socket with its chamfered corner directly above the chamfered corner of the silkscreen legend. This is because once the socket is soldered down, the 6811 only fits into it one way, so the socket must be soldered correctly.

6811 Pin Numbering

Several of the assembly steps require testing signals on the 6811 chip. This can be done either from the top of the chip, by inserting a thin wire to make contact with the actual 6811 leads, or from the bottom of the board at the PLCC socket leads.

6811 Chip Pin Numbering
TOP VIEW

Looking down at the 6811, the numbering of its pins proceed counter-clockwise from the pin 1 dot. E.g., pin 2 is immediately to the left of pin 1, and pin 52, the highest-numbered pin, is immediately to pin 1's right (see diagram above).

6811 PLCC Socket Pin Numbering
BOTTOM VIEW

There is a non-obvious translation from the simple numeric progression of the 6811 pin numbering to how the pins appear at the PLCC socket leads. The above diagram shows the pin numbering, looking up at the PLCC socket from the bottom of the PC board. In other words, the diagram shows the pin numbering assuming the board is turned upside down, and the viewer down at it.

Cutting Female Strip Header

Female strip header can be difficult to cut properly. If it is just snapped, it does not break cleanly between two pins; one pin adjacent to the break is generally destroyed.

A recommended method is to repeatedly score the header at the desired break point, using an X-acto or matte knife to gradually dig deeper and deeper into the cut line. Score the header several times on both sides of the groove between two socket pins until the header can be gently snapped by hand.

If done patiently, this process ensures clean breaks between the header sockets.

Fred Martin / MIT Media Laboratory / fredm@media.mit.edu / Tue Jul 16 14:36:59 1996