Most industrial machines run their limit switches on 24V to improve reliability. A noise must change nearly 12 volts before giving a false trigger.
In those situations, opto-isolation of the parallel port in very important.
If we run our limit switches on 5V only, it is unlikely to blow up the parallel port even if the BOB only use ttl buffers and NOT opto-isolation for the inputs. Limit switches at 5 volts can be more easily triggered by noise. A change of 2.4 volts can already cause a false trigger.
While I have NOT blown up any PC myself, I have customers returning PC with USB ports burnt or the Parallel port burn. When the parallel port is on the motherboard, the circuit nearby like the Ethernet and USB got burnt too. I had a cheaper PCIe parallel card destroyed too.
Customers do make mistakes. e.g. some would set the motion controller from USA to 110v and then plug into Australian 240v instead of the step down transformer supplied. The company that I sold PCs to, repairs a lot of blown external motion controllers by sending them back to USA for repairs.
Now I only sell PCs with AXXON 5V PCIe parallel Port cards from Canada which can withstand 15,000V without breaking down. They cost even more than ESS or UC300..but they are very robust for industrial use.
Guest
Poll
