Opt Isolator needed?

[kentken]

I am building a bale stroke counter for a farmer. It has a wire running from the cab to the magnetic switches on the baler. I am using PortB with pull-ups on a 16F872. Would it be a good idea to put in a optical isolator between the switch and the Pic???

Thanks

 

[Nigel Goodwin]

If you're running long wires about, it's probably always a good idea. However, presumably the baler uses a diesel engine , and it isn't as noisy an enviroment as using a petrol engine.

 

[kentken]

What is long to you? 6', 12' Most have diesel engines some in the front some in the center. Is there anything else to consider?

Kent

 

[Nigel Goodwin]

What is long to you? 6', 12' Most have diesel engines some in the front some in the center. Is there anything else to consider?

I would tend to try it and see what happens, using screened leads will help reduce any potential problems as well. Although using opto-isolators won't do any harm, and if you were designing a PCB for the circuit, you may as well include it on the board - then it's always available if needed.

 

[motion]

Magnetic switches? Are these sensors powered like those inductive proximity switches? In which case, they usually output a signal from 0Volt to 12V-24V. Unless they are the open-collector type without any other load, you may have to use optoisolators to bring the signal down to 0V-5V levels.

 

[kentken]

screened leads??? What's that?

 

[Nigel Goodwin]

screened leads??? What's that?

Like on a microphone, an inner core surrounded by a mesh screen - it helps prevent external interference getting into the cable.

 

[kinjalgp]

He is talkng about shielded wires.