Do not ground pins 3 and 5 of J1. They are shown not connected in the hook-up diagram and grounding them my damage the board. Only run wires for the pins that you actually plan to use with the 6500 boards, I.E. V+, Gnd, INIT, ECHO, and perhaps BINH. Connecting the extra pins with long wires causes them to act as antennas and pickup ambient EMF interference. One symptom of this is an constant echo time for all distances.
The ribbon cable is terminated with a connector that makes prototyping difficult. (It won't plug into a breadboard) The connector, will however, mate with a .1" machine pin socket strip (SIP). Cut two strips, one four sockets long and one five sockets long. Solder and insulate with heat-shrink 6 inch leads to the appropriate socket pins. This makes a reusable socket. Adding a larger piece of heat shrink tubing around the connector will help secure the wires.
Another and perhaps superior method suggested by Joshua Harris is to use a solder tail DB-9 connector:
"The 9-pin end of the ribbon cable plugs nicely into a female RS232C-type connector. The pins on the board then map to the pins on the connector as follows:"
Polaroid 6500 RS232C connector
Pin 1 --------- Pin 5
2 ------------- 9
3 ------------- 4
4 ------------- 8
5 ------------- 3
6 ------------- 7
7 ------------- 2
8 ------------- 6
9 ------------- 1
A common problem is determining which pin of the connector is Pin #1. The easiest way to do this is to use an ohmmeter to check for continuity between Pin #16 of U1 and the Pin #1 of the connector.
The ECHO output is an open collector driver which requires an 4.7 K pull-up resistor between the output and Vcc. This had the advantage that multiple boards can be connected to the same interrupt input. The pull-up is necessary for connecting the module to a digital input.
Parallax® BASIC Stamp® II App Note 6500-BS2.pdf Code Listing Correction: INIT CON should be 9 not 14 and ECHO CON should be 10 not 15.
8048 Microprocessor Source code: Son_8749.asm
by Doug Kelley The code
sample interfaces with the 6500 board and also implements a serial
interface and a stepper motor driver.
Microchip PIC App Note: 6500-PIC.PDF
and Source Code: 6500-PIC.ZIP
Salvaging the Sonar from a Polaroid 660 Camera: 660
Cam.pdf by Gary Croll
RS232 Serial Interface for the Polaroid 6500 by Peter Anderson
Arrick Robotics ARobot Sonar App Note
The 6500 board draws 2 Amp's during the short transmit period. A common source of problems is an inadequate power supply to handle the current inrush. This may cause a voltage sag leading to a microntroller reset. The solution is to provide the units with an adequate 5V power supply with generously sized filter capacitors. The voltage source does not need to supply the full 2 Amps if a larger filter capacitor is used (1000uF) and the firing rate is low.
In some cases were a bench top power supply is used, the power supply may enter into a current limiting mode. This can be avoided by using a larger power supply if necessary or simply increasing the crowbar current setting.