Hi, I am working on a water tank level indicator, I have found some projects on the internet but they install the display very close to the system. I will put an Arduino nano on the tank, and I want to control 5 led signals (which will determine the water level) 30 meters away from the tank, how can I connect 5 led's using a 30 meters cable?
wel,, you take one end of the cable and solder it to the arduiono and then you take the second end of the cable and solder it to the led. you repet the process with the second cable.
If you want to connect an LED to an Arduino, you will need a current limiting resistor or the pin or your LED or both will be destroyed fairly swiftly. 220 ohm is a common choice for the LEDs you'll find in an Arduino kit.
The problem with long wire runs is that wire has non-zero resistance and if long enough, will cause enough of a voltage drop that whatever is at the far end doesn't get the juice it needs.
Happily for you, you can use these two facts to your advantage. Hook up your Arduino and LED via the 30m cable with a resistor in series. If the LED is dim, reduce the resistor value a bit to compensate.
30 meters away from the tank,
Is that 30m as the crow flies or 30m of cable? A cable run can be more distance due to routing along structural members, ie. going up to the ceiling/roof and back down, etc.
No way do you want to connect the 30 meter wires to the arduino, you are asking for weird problems and blown Arduino. The EMI etc on those 30 meter antennas will kill you. Use something like a stepper motor driver board ULN3003 and either modify it for five outputs or use two. You can use MOSFETS, transistors but do isolate the wiring from the Arduino. At this point I am assuming you have a voltage greater then 5V DC, if so use it. Connect the Positive power supply to the anodes of the LEDs, the cathodes to the ULN3003 using a resistor. then connect the inputs appropriately. Go on line and look up the resistance of 60 meters of wire (it is 30 in each direction). Now calculate the amount of resistance you will need, be sure to include the wire resistance. Here is a calculator: LED Resistor Calculator This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Another option might be a wireless connection from the Arduino at the tank to a second Arduino that operates the LEDs.
I think a TPIC6B595 would be a suitable buffer to feed the cable.
Kudos to zwieblum.
The EMI etc on those 30 meter antennas will kill you.
This is a joke, right?
I was also thinking wireless. Two NRF24 modules should easily bridge that distance, those plus the second Nano cost you probably less than the wires (5 LEDs = 6 core wire - if you use thin signal wire you may not even need resistors, as the wire offers quite some resistance by itself), and is easier to install. I do assume you have power available at both ends.
For the wireless part, of course it matters if there are obstacles like walls in the way and what they're made of. You can test this quite easily: place a WiFi router at one end, take your phone to the other end, and see if you can connect. If that works, NRF24 is very likely to work as well.
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Is it necessary to have the Nano at the tank?
What are you using as a level sensor?