Cables - Robot DHQ

    

(Please note that what some people call a plug is what I call a socket, and vice versa!)

Cable Description

All ribbon cables used in the Robot-DHQ design are electrically identical standard ribbon cables. Pin 1 goes to pin 1, etc. The only difference should be the length of the cable. It is possible to have reversed cables. It is up to you to know which is which and keep them separate if you have both kinds. You may have undesirable results if you get these mixed up.

The standard ribbon cable assembly has ten conductors and is terminated at each end by a 10-pin IDC plug with a tab so that it can only plug one way into a corresponding shrouded PCB socket.

The IDC plug tabs face the length of ribbon cable and if the cable is short it will be apparent that the two tabs on the ends of the cable face each other. Also, the IDC plugs are on opposite sides of the ribbon cable. From the side, the cable assembly resembles a Z or N. This arrangement means that it does not matter which end attaches to which board. The conduction paths are the same either way.

One way to verify and understand this is to loosly fold the ribbon cable on itself and match up the two IDC connectors, side by side. Pin 1 is pin 1, etc.

It does matter, however, what type of boards are being connected. Connecting two output signals will generally cause one or both to overload and the on-chip drivers, one or both, will burn out. See Table 1.

The shrouded PCB socket is always oriented on the edge of the PCB so that the tab slot in the shrouded socket faces the near edge of the PCB. This means that the ribbon cable should always extend away from the PCB. It matters whether the socket is mounted on the top or bottom side of the PCB. That is why the sockets are always presoldered on the PCB by the supplier. The shrouded PCB sockets are mounted on the top of the ANBb, the Arduino Nano Breakout board. The socket is mounted on the bottom of the QPb, the Quad Pot board. It is mounted on the top of the BAb, the Breadboard Adapter board.  

This top bottom arrangement means that ground is the center pin closest to the edge of the board on the ANBb and BAb, but it is the center pin away from the edge on the Qpb. It appears that pins 5 and 6 have switched places when looking at the top side of the PCB. Likewise pins 1 and 2, etc.

To better understand and visualize this, place a QPb and ANBb side by side on the table in front of you. Have the top side of ANBb up and the top side of QPb down. Rotate the QPB so that the orientating slot of two sockets face the same direction. The upper right hand connector will be wired to the upper right hand connector when a cable is attached knowing how the cable is constructed, etc. Now invert the QPB by rotating it along its longest axis. The conductor in the upper right hand corner is now in the upper left hand corner. The center pin closest to the edge of the ANB board is ground. The center pin furthest from the edge of the Qpb is ground and they will be connected.  From the top of the board it appears that pin 1 and pin 2 have switched places, etc.

The numbering of the pins is with reference to the ribbon cable. The conductors are numbered sequentially accross the width of the cable. Conductor #3 is always +5 volts. Conductor #6 is always ground. The other conductors carry various signals that vary from board to board and socket to socket. Look at the breadboard adapter for quick reference. This board has the conductors numbered. The cable, plug and socket arrangement helps ensure that +5 is never connected directly to ground but this cannot be guaranteed. Too many things can go wrong.Follow the description given here to help understand the connections when contructing your application. A casual inspection can lead you down a wrong path.  

Table 1. A list of sockets and the sockets to which they are typically connected.

 

Arduino Nano Breakout board

A

Quad Pot board, Breadboard Adapter board

B

Quad Pot board, Breadboard Adapter board

C

Breadboard Adapter board

D

Quad Pot board, Breadboard Adapter board

E

Quad Pot board, Breadboard Adapter board