What's an eddy sensor? I know they're used on some Williams games. On my RFM it's used in the inner loop, if I'm not mistaken. I've tried looking up info online but haven't found anything.

How do they work? Who invented them? (Brian Eddy?) Are they not used by Stern due to patents?

What exactly are "EDDY SENSORS"? They are Electronic Ball Sensors. Around 1993 Williams started using them. What do they do? They are basically a circuit board with some stuff on it, mounted under the playfield at a position where a "normal" switch would have been, and they simply sense when a pinball rolls over it, and acknowledge to the CPU it happened. Just like any other switch. But, it's electronic, man.. And it's a Sensor, not just some wimpy switch. Yup, good stuff, oh, yeah, so high tech.

More infos and pictures here : http://www.txpinball.com/eddy_sensors_troubleshooting.html

Took me 1 and a half second to Google it

THE RFM ones are actually magnets.  I find them really finicky as hell, if you look under you rPF where that inner loop is you will see two black logs (best way I can describe them) pushed right up against the bottom of the PF.  What they do is act like a switch, when the sensor senses the magnetism of the ball it registers a hit, problem is I've never found them to be very reliable in RFM.

CV has them, Roadshow has them. NGG has them, they work better on those machines, but the difference is on those machines they are in front of a dead stop so the sensor has more time to pickup that the ball is there.  On RFM it's a straight threw shot so the speed of the ball makes it harder for the sensor to pick it up.  

Scared Stiff uses on as well right in front of the "Crate" door.

They work well, and in Scared Stiff it actually has an associated circuit board that works with the sensor, this board has a pot that allows you to increase the sensitivity.... sweet....

Yes, I know they're sensors, yeesh.

So they use magnets? That's weird because in switch test mode I was able to activate the inner loop switch by placing my finger in the loop.

They are magnetic inductance sensors. They pick up the change of the magnetic field caused by the passage of ferrous metal (i.e. the pinball) over the sensor. They seem to be used mainly in locations where optos won't work, or aren't practical. How well they work seems to depend on the machine and the specific sensor. The Truck eddy on my ToM works really well, the outlane eddys are very hit-or-miss.

Quoted from Vengeance

THE RFM ones are actually magnets.  I find them really finicky as hell, if you look under you rPF where that inner loop is you will see two black logs (best way I can describe them) pushed right up against the bottom of the PF.  What they do is act like a switch, when the sensor senses the magnetism of the ball it registers a hit, problem is I've never found them to be very reliable in RFM.

CV has them, Roadshow has them. NGG has them, they work better on those machines, but the difference is on those machines they are in front of a dead stop so the sensor has more time to pickup that the ball is there.  On RFM it's a straight threw shot so the speed of the ball makes it harder for the sensor to pick it up.  

Part of the problem with the eddy sensors used in RFM are not actually the sensors themselves but the CPU that is sensing the switch closure.  This is a known problem with all P2K machines as the CPU will not recognize some / all quick switch closures, something to do with the rate at which is strobes the switch matrix if memory serves correct.  Basically it's an OEM hardware limitation.

The good news is there is a solution to the problem.  It's called Nucore.    (Nucore fixed the missed switch closure issues)

D