Portable spa monitoring and control circuitry
US9006616B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jun 19, 2012 |
| Grant date | Apr 14, 2015 |
| Priority date | — |
| Expiry date | May 25, 2033 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05B1/025
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
Control circuitry for controlling a spa water heater, wherein a microcontroller is configured to detect zero crossings of an A.C. line voltage from a voltage sense signal, to cause closing of a first heater relay and a second heater relay, to detect the time at which heater current is initially sensed by a current sensor after the initial closing of the second heater relay, to measure a time delay between the time that the second heater relay is closed and the time at which heater current is initially sensed, and to adjust the time at which a second closing of the second heater relay occurs such that zero crossings of the heater current occur at the same time as zero crossings of the voltage waveform. The control circuitry further includes a voltage sense circuit comprising a first diode connected in series with a current limiting resistance connected in series with a Zener diode, which is in turn connected in series with an optical coupler LED.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.