Long signal lines in Arduino- help needed - Page 1
Forum section: electronics / general

author: rodd
author_rank: Regular Contributor
timestamp: January 08, 2017, 11:22:30 pm
content: Hi,I am starting with arduino, but have experience with electronics and programming in Fortan (yes, I am old...).I have one water tank and a booster pump that are located 60m from my house.The pump sends the water to another reservoir that is located 30m of the house in another direction.I intend to monitor the level in the two reservoirs using HC-SR04 ultrasonic sensors and read the level in an lcd display located inside the house where the Arduino Uno board will be located.So here is the question:Is it possible to send the sensor signals along non shielded data cables (the are already buried) to the arduino board?Any problems of noise pickup or data loss expected in this situation?Any design recommendation or suggestionEnviado do meu iPhone usando Tapatalk

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: January 08, 2017, 11:48:45 pm
content: Use differential lines with suitable line drivers/receivers, plus some protection devices (transorbs, GDT or varistor). I would grab a cheap Arduino Nano clone and put it at the reservoir end to read the sensor data and translate it into serial messages sent down the differential line as RS485/422. The Uno would have a shield with a line receiver to convert back to single-ended, fed into the UART for further processing/display. Twisted pairs are nice, but RS485 will work without them if you keep the baud rate low enough.

author: akos_nemeth
author_rank: Contributor
timestamp: January 09, 2017, 12:41:03 am
content: Hi rodd,What about cheap 433Mhz tranceivers from ebay:http://www.instructables.com/id/RF-315433-MHz-Transmitter-receiver-Module-and-Ardu/The unshielded lines could be used for the power supply.Regards,Ákos

author: BrianHG
author_rank: Super Contributor
timestamp: January 09, 2017, 12:47:33 pm
content: Quote from: akos_nemeth on January 09, 2017, 12:41:03 amFor this one, it's unidirectional & you would need to add error correction & garbage data rejection algorithms.For a RS485 serial port on 2 wires, this IC at each end should work: SN75HVD3082EPEasy to work with since it's an 8 pin dip.

author: Psi
author_rank: Super Contributor
timestamp: January 09, 2017, 12:49:43 pm
content: Cheap 2.4ghz module might be better. Most are bi-directional and some have built in error checking/pairing. So you just get an easy to use serial link between the two micros and dont have to worry about your own error checking/garbage rejection.

author: Ian.M
author_rank: Super Contributor
timestamp: January 09, 2017, 01:12:22 pm
content: 60m lines between different structures outdoors are likely to see high transient voltages if there is a nearby lightning strike. In addition to the recommendation to use RS485 transceivers, I strongly recommend using optoisolators between the MCUs and the transceivers and an isolated DC-DC converter to power each transceiver, taking care to preserve the maximum possible creepage and clearance distances between the isolated transceiver and the rest of the board. Add a well grounded data line surge suppressor to each end of each buried line and it will have a reasonably good chance of surviving a near-by strike.

author: BrianHG
author_rank: Super Contributor
timestamp: January 09, 2017, 02:11:27 pm
content: Quote from: Ian.M on January 09, 2017, 01:12:22 pmYup, totally ignored that outdoor nature of the 60m wiring. Thanks for pointing that out. Even using the 60m wiring alone for delivering a power supply can be randomly problematic when going between structures in the outdoors.