I need to communicate with a device through a 200m multiconductor cable. Some of the cable conductors are used to power motors via a VFD. There will be A LOT of EMI in the cable. Assume worst case, there will be no shielding on the comms bus conductors (although there probably will be).
Is there ANY comms bus hardware protocols that are guaranteed (or highly likely) to tolerate this crazy high EMI environment? Please do not suggest fiber optics. I already know that is the best solution but I am trying to find a simpler and cheaper alternative. Please do not suggest wireless. That is not an option for this application.
Here's what I'm considering so far (in order of what I think will work best):
Thank you
Chuck
Is there ANY comms bus hardware protocols that are guaranteed (or highly likely) to tolerate this crazy high EMI environment? Please do not suggest fiber optics. I already know that is the best solution but I am trying to find a simpler and cheaper alternative. Please do not suggest wireless. That is not an option for this application.
Here's what I'm considering so far (in order of what I think will work best):
- Ruggedized industrial comms busses such as Power rail boosted Profibus and Dupline.
- Assumption: If it's designed to operate out to 10km, over slip rings and bus bars adjacent to power bus bars, and if it makes claims of "exceptional noise immunity" or "immune to noise" then maybe it lives up to its claims and maybe it has a chance.
- Point-to-point pair of "ethernet extender" DSL modems ranging from this to this.
- Assumption: if it's designed to operate over a 20,000m aerial antenna (suspended phone line) adjacent to power lines, then it should be able to operate through only 200m of exceptionally noisy cable.
- EoP (ethernet over powerline)/BPL(broadband over powerline) with solutions ranging from this to this.
- Assumption: if it's already designed to communicate ON noisy power lines, it should be able to handle comms over a clean isolated sine wave NEXT to noisy power lines.
- A homebrew amplified serial connection involving optically isolated transceivers and high current, low impedence I/O.
- Assumption: If serial clock and data lines are optically isolated (responding to current flow instead of voltage fluctuations) with very low impedance (requiring a relatively very high current, tens or hundreds of mA) to change state, then EMI would not be enough to cause inadvertent state change or prevent intended state change.
- Multiplexed 4-20mA analog signals or HART modem
- Assumption: same as above, current instead of voltage driven signal, should be more EMI tolerant.
- Typical industrial protocols (CAN Bus, MODBUS, RS-485/422 variants - devicenet, profibus, etc.), via Isolated repeater or not.
- Assumption: these protocols are differential signals with high common mode rejection. Any EMI that affects one wire affect the other as well. They are proven tech in industrial settings and may be sufficient.
Thank you
Chuck