Hi All,
I recently acquired an inductive proximity sensor designed for industrial applications.
The unit has two terminals and runs on 10..55V DC.
All you need to do to connect it up is place a load (relay etc) in seres then apply power.
The interesting property is that wired one way around the unit is normally open (apply a metal plate to the sensor and it switches on). Wired the other way around and the unit is normally closed (apply a metal plate to the sensor and it switches off).
The unit claims a maximum dropout of 2V.
This poses some interesting design issues:
My first inclination was that the terminals of the unit went through a full wave bridge before the drive electronics. This won't work, you have just lost 1.2V across the bridge and I doubt if you can run the electronics on 0.8V.
Second thought was that there are two complete systems within the unit. One for the 'positive' polarity (NPN) another for the 'negative' polarity (PNP). Each system is designed with opposite output drive sense.
Anyone have any other thoughts on topology for this device ?
See
Regards,
Mark