Voltage detection system and method
A sensing device is for sensing an operating voltage of a remote device. A communications interface receives communications signals originating from the remote device over a communications bus. A data sampler takes data readings of a communications signal at a predetermined set of timing instants defined by the sensing device. A data metric (such as a duty cycle of high and low states) is obtained from the data readings and from this 5 an operating voltage of the remote device is obtained, based on a relationship between the voltage and the data metric. The invention is based on detecting timing changes which result from voltage changes. In particular, the slope of rising and falling edges of the communications signal are influenced by the voltage level, and this in turn influences the timing of high states (1s) and low states (0s).
1. A voltage sensing device for sensing an operating voltage of a remote device, comprising:
a communications interface for receiving communications signals originating from the remote device over a communications bus;
a timer;
a data sampler for taking data readings of a communications signal at a set of timing instants defined by the timer; and
a processor adapted to determine a data metric from the data readings and to determine from the data metric an operating voltage of the remote device based on a relationship between the operating voltage and the data metric.
2. The device as claimed in claim 1 , wherein the communications interface is a unidirectional interface for only receiving the communications signals.
3. The device as claimed in claim 2 , adapted to perform a calibration process at a known operating voltage or voltages of the remote device.
4. The device as claimed in claim 1 , wherein the processor is adapted to determine an operating voltage by applying the determined data metric to a stored function or look up table representing the operating voltage-data metric characteristics of the remote device.
5. The device as claimed in claim 1 , wherein the processor is adapted to filter the data readings such that the data metric is derived from data readings which all relate to:
a 01 transition; or
a 10 transition; or
either of a 10 and 01 transition,
of the communications signal.
6. The device as claimed in claim 1 , wherein the data metric comprises a duty cycle of 1 and 0 values of the communications signal.
7. The device as claimed in claim 1 , wherein the timer as a clock frequency higher than the bit frequency of the communications signal, for example in the range 2 to 10 times the clock frequency.
8. The control system for a lighting system, comprising:
a lighting system controller; and
a voltage sensing device as claimed in claim 1 .
9. The lighting system, comprising:
a control system as claimed in claim 8 ; and
a set of luminaires which are connected to the control system by the communications bus.
10. A voltage sensing method for sensing an operating voltage of a remote device using a voltage sensing device, comprising:
receiving a communications signal originating from the remote device over a communications bus;
taking data readings of the communications signal at a set of timing instants defined by a timer of the voltage sensing device; and
determining a data metric from the data readings and determining an operating voltage of the remote device based on a relationship between the operating voltage and the data metric.
11. A method as claimed in claim 10 , comprising receiving the communications signal over a unidirectional interface.
12. The computer program comprising code means which is adapted, when said program is run on a computer, to implement the method of claim 11 .
13. The method as claimed in claim 10 , further comprising performing a calibration process at a known operating voltage or voltages of the remote device.
14. The method as claimed in claim 10 , comprising filtering the data readings such that the data metric is determined from data readings which all relate to:
a 01 transition; or
a 10 transition; or
either of a 10 and 01 transition,
of the communications signal.
15. The method as claimed in claim 10 , wherein the data metric comprises the duty cycle of 1 and 0 values of the communications signal.