hi,
I was wondering why one of the motion sensors (HR100 hotron) that we use on auto doors which is fitted with a transistor switch NPN can handle both switching the negative and positive side of a circuit. The theory says that a npn can only switch to ground and pnp to positive but why when we wire that sensor's npn transistor to switch to positive, it works too.
I even emailed hotron about this and they confirmed that it is a npn transistor (so as the manual) and it could interface with door controllers with 24vdc signals.
????? now I am confused. why would we have two types of transistors with two specifics functions if one can actually perform both.
is there anything I am missing here? is there any specific wiring to make those transistors more flexible
perhaps?
thanks for your expertise
I was wondering why one of the motion sensors (HR100 hotron) that we use on auto doors which is fitted with a transistor switch NPN can handle both switching the negative and positive side of a circuit. The theory says that a npn can only switch to ground and pnp to positive but why when we wire that sensor's npn transistor to switch to positive, it works too.
I even emailed hotron about this and they confirmed that it is a npn transistor (so as the manual) and it could interface with door controllers with 24vdc signals.
????? now I am confused. why would we have two types of transistors with two specifics functions if one can actually perform both.
is there anything I am missing here? is there any specific wiring to make those transistors more flexible
perhaps?
thanks for your expertise
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