Purpose of the Signal Booster
In order to get sufficiently fast and glitch-free throughput to run all four axes of a CNC system at the same time, multiple wires are needed. That is why we use a 25-pin parallel port to transmit the information rather than a serial port like USB. However, it has recently come to our attention that some users of our 8760 driver box are having problems when using them with their own computer*. Signal output through the parallel port on computers should be about 3 volts, but some poorly made cards and connectors may put out only a marginal signal. Also, the signal may decrease with the age of the computer or when it gets overheated. A symptom of this is that one or more stepper motors may suddenly change direction, run in only one direction or act erratically in other ways. This has not been a problem with any computers sold by Sherline—only when connecting the Sherline driver box to a computer with a parallel port of unknown quality. To help those with problems with parallel signal strength, Sherline has developed an amplifier to boost the signal strength. This is, in most cases, more economical than trying another computer.
*NOTE: Dell computers seem to have a lot of difficulties with the Linux OS installation.
Connecting the Signal Booster
The male side of the parallel connector is plugged into the printer port on the user’s computer. The parallel cable to the driver box is then plugged into the female side of the parallel amplifier. The USB cable is plugged into an open USB port on the host computer to power the amplifier.