Still alive and kicking.
My autogate system is still working like a champ many years later. My system is distributed- no central controller, no PLC, etc. Each gate is independently operated. Current sensors are mounted at each outlet where a WW machine is located. A central 24V transformer powers everything.
When a WW machine is turned on, the sensor (a small torroid with integral PNP/NPN transistor switch by CR Magnetics) detects the machine's current draw and generates enough current of its own to operate the transistor switch. The switch closes and 24V is routed to a pneumatic solenoid. The solenoid draws very little current, only 120 mA(?) so doesn't tax the switch. The solenoid allows shop compressed air, regulated to a low 15 psi, to open the cylinder that operates the gate slide. Since the psi is low the pneumatic solenoids and cylinders are plumbed with inexpensive vinyl tubing. The solenoids and cylinders are dual acting so in the unpowered state air powers and holds the gate closed.
When the solenoid opens, a current sensor switch on the 24V transformer causes the DC to start and stay running- intentionally. It is connected via an existing 3 wire low voltage, manual control, latching circuit that I retained so I can use the DC to vacuum, etc. I never bothered/decided not to wire in a delay on break relay so I must hit one of the 6 or so stop buttons located around the shop when I want to shut down the DC. There are times when I want the DC to remain running while a prepare a cut and didn't want it shutting off before I was sure I was done.
There used to be a nice video of it I did for American Woodworker posted on their website, but with their demise it is gone and I can't find my original. I don't think Pop Woodworking which purchased AWW has it either. Google me and you should find a bunch of threads on various forums about my system, some with photos that are hosted on NCWWer. Alan Schaffter, automatic dust collection. Here is a fairly decent thread with photos:
Autogates Yup, I am the same guy behind the INCRA I-BOX jig for making box joints and the Infinity Lock Miter Master jig for setting lock miter router bits.