Max Long of Wired Between Arduino and Sensors

Projects General Guidance
1

hii every body

i need the answer for most wanted questions on the ardunio world

i need to know the max Long of wired and the size of it between arduino and any sensor (analog or digital)

an example :

if i have PIR Sensor conneted to my arduino , as we know this sensor need 3 wire

-GND
-VCC 5 V
-Signal as input to arduino on Digital Pin like (Pin 13)

if i want to connect all 3 wire to arduino directly

my questions is :

what it the long wire i can reah between arduino board and PIR sensor for each wire (VCC,GND,SIGNAL) , and how much the best width of wire (? mm) ?

can i use cat5 wired (Network Cable) to this mission or not good ?

thanks for every one

2

Cat-5 is perfect, and you could probably bridge 10km if you had to.
Use one pair for 5volt and ground, and another pair for signal and ground.

For long lengths (more than a few meters), use a 100n ceramic cap from Arduino input pin to Arduino ground.
Leo..

3

Thickness of the cable depends on the amount of current your device draws. More current, thicker cable, or your losses become too much. Cat-5 can't carry much current.

Wawa:
For long lengths (more than a few meters), use a 100n ceramic cap from Arduino input pin to Arduino ground.

What's the purpose of this cap?

4

wvmarle:
Cat-5 can't carry much current.

What's the purpose of this cap?

A PIR sensor draws ~70uA.

Long wires act as antennas. The cap shorts any RF to ground.
Leo..

5

wvmarle:
What's the purpose of this cap?

Noise attenuation.

Depending on the data rate, you may need to treat the line as a transmission line and use matched impedances at each end. (Matched to the cable's characteristic impedance.)

6

thanks to every body ..

so what i guess is :

i can use 100 Meter of Cat5 to link arduino to PIR Sensor or any Sensor and use 100 nf Ceramic Capacitor to reduce the attenuation . is that right ?

if i use external wire like electric wire i can use over 100 Meter with thickness 1 mm to transmite 5 volt from arduino to PIR Sensor , and get Signal from Seneor back to Arduino is that right ?

if any best idea i waiting for it

thanks again ....

have a nice day

7

The simple answer is "yes" but, depending on the electrical noise nearby, you may need to do more work.

Is this going between different buildings? Then you have to consider lightning protection. Lightning can hit nearby and induct significant currents into your wire.

8

The simple answer is the relationship between the resistance of the cable, the voltage and current needed to signal to the other end, and any effects external RFI may have.

Running digital signal cables next to lift power cables for example cause a few issues because of induced voltages during switching.

Mostly the device manufacturer will indicate recommended cable etc., in your case it seems you will have little current draw so CAT5 will probably work just fine.

Professionally sensors are generally installed using 1.5mm2 conductors (1.0mm2 is more than adequate), but that is as much for mechanical strength as low resistance, a 10K NTC v. 100m of line drop is insignificant. Also they tend to use either 4-20mA drivers or 0-10V sources for analogue sensors with 24Vac supply.

Digital signals are usually defined in the hardware layer, so typically RS232 has a normal limit of 15m, RS485 1.5km, ethernet nominally 100m. But they can often be pushed, it depends what is around them.

As MorganS noted, if going between buildings - do it underground! Lightning makes a big mess.

9

Even underground is susceptible to lightning strikes. But it is safer. If there's a 1000V pulse on the cable then it will probably discharge to ground after damaging your Arduino. This makes it less likely to start a fire inside your house.