Tackling the power challenges of the smart home

September 06, 2019 //By Nick Flaherty
EMI challenges from the power supply compromised smart cameras in a holiday home and can be solved by a filter
EMI challenges from the power supply compromised cameras in a holiday home

Alan Beale understands the smart home. He installed a security system, with remotely-accessed cameras both inside and outside of his holiday home in Cyprus. He ran the camera data through an EtherCAT system with networked devices, instead of the home’s existing CAT5 system or unstable Wi-Fi. But the challenges to the smart home system reliability actually came from the power system.

The cameras started to malfunction, some worked while others didn’t, and the reasons for this were unclear. Suspecting the problem might be the power supply, Alan called an electrician to examine the issue. It took two days to understand the problem.

Eventually, they realised that the only other power-related change to the house had been its swimming pool heater system. The previous, failing system had been replaced with a new inverter-based phased heater, which saves electricity by varying the speed of the current. The pool heater worked fine, but the inverter was causing harmonic interference in the mains cabling. This was affecting the security cameras.

“In hindsight it was obvious,” said Beale. “We switched the heater off and the cameras started working. The problem was more difficult to spot because there’s a three-phase electrical supply to the house, to power the air conditioning and so on. It would have been more obvious with a single-phase supply.”

Nevertheless, Alan was unsure how the interference problem could be solved across his smart home. “I was worried that I’d have to send the pool back and go with a non-inverter system. They are hefty pieces of kit, around 100 kilos, and can cost around £4,000,” he said.

Instead, he contacted filter developer REO in the UK, which recommended the CNW 541 single-phase mains electromagnetic compatibility (EMC) low-pass filter. The EMC filter allows the mains frequency to pass through with very little attenuation. The inverter on the pool system caused EM noise, so using the CNW 541 on the input of the inverter would reduce these emissions and clean up the supply.

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