Simple humidity sensor with ~50m wire

This is my first post on this forum, so hello everyone! :slight_smile:

I'm designing simple garden watering system and I need to measure humidity of soil.
The problem is that arduino will be located in garage so the wires of sensor (planned FC28) has to be about 50/70 meters.
I know that this distance eliminate simple analog-in read.
Is there any solution to measure humidity on this distance?
I don't want to use digital conventer, which gets me HIGH status if humidity increase some level - I want to display humidity in "%" on screen.
I heard about 4-20 mAmps method but I'm not really understand how to design it on arduino with this sensor.
Thanks for attention :slight_smile:

could you have an Arduino local to the humidity sensor which transmits data to an Arduino in the garage over a serial line using an RS232 shield, a RS232 to TTL Serial Module or a TTL to RS-485 Module ?

onlybike:
I know that this distance eliminate simple analog-in read.

Is that so? I don't see why that would be. It's just a voltage level, very little current so very little cable loss.

onlybike:
I heard about 4-20 mAmps method but I'm not really understand how to design it on arduino with this sensor.
Thanks for attention :slight_smile:

the 4-20mAmp Arduino shileds are not cheap (about £60) - I would have thought a nano at the sensor connected to a Uno in the garage using RS-485 would be cheaper

Have you conquered a wireless connection? A Nano with a RF24 radio sending the data to the main unit with another RF24.

At 50 meters, wireless is typically cheaper than the cost of the cable.

RS485 sounds simpler to me.

edgemoron:
the expense of converter modules,

RS435 to serial converters go as cheap as USD 0.13 a piece, so that can't be a deal breaker.

suitable cabling,

Nothing special about the cable - twisted pair will do just fine.

termination resistors,

I recall I paid the equivalent of about USD 1 for 1,000 pcs. May be included in those RS485/TTL converters already.

multidrop connections, cable routing from one unit to another that may not be convenient. Lots to consider besides ease of programming. :confused:

OP mentions just one sensor.