QuarterHorse – Optoisolator Install and Use


On some vehicles, the QH doesn’t work well due to an excessive amount of electrical noise or ground potential differences.  In these cases, the optoisolator module we sell provides electrical isolation between your laptop and the QuarterHorse.  While not a solution to electrical noise issues on the vehicle, it certainly can help.

The main workflow change that this creates is a need to have the QH powered on whenever communicating using the opto cable.  If you need to load a base tune on the bench, you can still plug in to the USB cable directly but you will not have any isolation.  Then again, you shouldn’t need it on the bench.  Please don’t try to have both the Optoisolator interface and the standard USB interface plugged in at once.  It shouldn’t break anything, but it also shouldn’t work.


In order to use the optoisolator interface with the QH, you must solder a 4 pin right angle latching header.  You should have received one with the optoisolator kit.  Email us if you require extra latching pin headers.

First, place the pin header in the QH, oriented as shown here:


Viewed from the bottom:

Next up, solder the 4 pins.

View of completed QH with header for Optoisolator module:

Once the header is installed, simply connect the supplied 4 pin latching header between the QH and the optoisolator module.  Plug the USB end of the optoisolator module in your laptop and get back to tuning.  The isolator module uses the same USB drivers as the QH.