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Topic: 5V parasite problem on long wires and environmental effects (Read 609 times) previous topic - next topic

atraks

Hi guys.

Im using pic on some industrial projects. Getting pulse from sensors with reed switch is one of them.

Im getting wrong pulse signal because of environmental effects or cable long.

Is there any way to get this signal without parasit?

My wires is 10 meter but it surrounded by power cables for big machine.So they have magnetic field.

24 v circile with relay can be solution for that?

I heard capacitors can be used for that, do u have any filter solution?

Im using this diagram...

https://www.google.com.tr/search?tbm=isch&sa=1&ei=vF1bW5HoOsaPsgH67KSIDg&q=arduino+reed+switch+&oq=arduino+reed+switch+&gs_l=img.3..0i19k1j0i30i19k1l2j0i8i30i19k1.158106.158106.0.158304.1.1.0.0.0.0.159.159.0j1.1.0....0...1c.1.64.img..0.1.158....0.DwsNBYMyw2U#imgrc=SV9vNvuFCmjWhM:

Paul_KD7HB

That is what they make metallic conduit. Put your data cable in conduit.

Paul

atraks

Is there any other solution for that? Cost can be problem for that, Cable is 10 metres.

Paul_KD7HB

Is there any other solution for that? Cost can be problem for that, Cable is 10 metres.
There are always other ways. Use a radio link that can cover the distance. But then you need two Arduinos and two tranceivers.

Paul

allanhurst

What value of pullup/pulldown resistor are you using? A low vale is better - say 1k.

Plus ferrite beads can be a help.

And a capacitor across the arduino input to ground -  eg 100n.

Using screened cable can also help, as would twisting a pair of wires tightly.

You can buy audio twinscreen which has a twisted pair inside a conductive sheath - it's very good at rejecting interference.

Allan

hammy

I would optically isolate the inputs , really best way to avoid spikes , noise and other pickup problems .
IMO it's not a great plan to run long leads directly to a microprocessor for that reason
Sparkfun do some opto isolators breakout boards .

LandonW


MarkT

My wires is 10 meter but it surrounded by power cables for big machine.So they have magnetic field.

This is a big problem - sensor cables shouldn't be running alongside power cables!  Separate conduits would help, shielding is mandatory otherwise (only ground the shield at one end though, or you just get a big nasty ground
loop).

To help condition a slow speed input, fix a 100nF capacitor from the pin to ground at the Arduino, and add
100 ohm resistor in series at the Arduino to deaden reflections.   These two precautions together will greatly
reduce noise spikes on the line and multiple triggering from reflections.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

allanhurst

Twisted pairs are very good at rejecting magnetic interference.

Audio twinscreen even better.

An opto is also a good idea.

Allan

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