Log distance Signal

If I have two Arduinos 50m apart and send a HIGH signal on one will it be received by the other even though it is so far away? Do i need a pull down resistor?

assume using 1mm house electric wire.

Thanks all.
Brendan

O/P to I/P requires no resistor.

You do know you will need a common ground return path between the two Arduinos?

You need two wires, signal and ground. For low data rates, 50m is no problem.

Thank you

so no need for the resistor.

I have a common ground so thats no problem either.

thanks
Brendan

BTW, using an opto coupler can prevent ground loop problems.

A 6N137/138 is a good choice.

+1
There is the risk of phantom powering (if one is on and the other one is off).
I would use an opto coupler, as larryd suggested.
Use the opto at the receiving end (near input pin).

Opto emitter to ground, collector to pin, pull up enabled on input pin in setup().
pinMode(optoPin, INPUT_PULLUP);
2-core wire from opto LED to other Arduino.

On the transmitter Arduino.
LED cathode wire there to ground, 1k resistor between output pin and LED anode wire.
Leo..

Hi all (thank you for the responses)

all arduinos would be powered from the same power supply so phantom powering shouldn't happen.

however just to ensure I got your description correct for others can you please check my schematic.

R1 may need to be lower, 220 Ohms or so. You will need INPUT_PULLUP or a 10K pullup resistor on D13.

If you use a 6N137 example:

For that long a run an optocoupler is wise, to prevent spikes destroying either Arduino when there is nearby lightning or heavy mains switching transients.

madguernseyboy:
all arduinos would be powered from the same power supply so phantom powering shouldn't happen.

Then forget about the opto coupler, and use shielded wires or twisted pairs for data and power. Cat-5 is cheap.
I hope you don't have any interfering sources near.
Leo..

madguernseyboy:
can you please check my schematic.

The whole idea of an opto coupler is to have no ground link between devices, to prevent ground loops and interference.
Cut the short ground link under the opto in the diagram.
You now must have two separate supplies. A 5volt phone charger connected to the USB socket could do.
Leo..

larryd:
O/P to I/P requires no resistor.

You do know you will need a common ground return path between the two Arduinos?

As long you don't use mains to power it, you can just shove a wire into the earth and connect it to the arduino ground. This will cause the arduinos to have a common ground without another wire.

I must ask you a question:
Have you considered a radio transmitter. You can get a sufficient pair for under 10 dollars.

As long you don't use mains to power it, you can just shove a wire into the earth and connect it to the arduino ground. This will cause the arduinos to have a common ground without another wire.“

OMG, but I live in the middle of the Sahara Desert :frowning: .

larryd:
As long you don't use mains to power it, you can just shove a wire into the earth and connect it to the arduino ground. This will cause the arduinos to have a common ground without another wire.“

OMG, but I live in the middle of the Sahara Desert :frowning: .

You may be out of luck. The ground needs a little bit of moisture. Sorry.