Field adjustable output for dimmable luminaires
A field adjustable output control usable with a luminaire to adjust dimming employs a first resistance source, and at least a second resistance source, and a shunt voltage regulator having a reference node coupled between the first and the second resistance sources to form a voltage divider that provides a reference voltage to the shunt voltage regulator, wherein the shunt voltage regulator is electrically coupled between an LED driver dimming line and a ground via first and second nodes of the shunt voltage regulator to regulate a flow of current from the LED driver dimming line based on the reference voltage supplied via the voltage divider. The second resistance source can take the form of a plurality of discrete resistors, each having a respective value of resistance, or alternatively can take the form of a potentiometer having a continuously variable value of resistance associated therewith.
1. An apparatus, comprising:
a first resistance source;
a second resistance source electrically coupled in series with the first resistance source, the second resistance source selectively operable to vary a value of resistance provided by the second resistance source;
at least one switch operable to selectively adjust the value of resistance provided by the second resistance source;
a shunt voltage regulator having a reference node, a first node and a second node, the reference node coupled between the first resistance source and the second resistance source to form a voltage divider that provides a reference voltage to the shunt voltage regulator, wherein the shunt voltage regulator is electrically coupled between an LED driver dimming line and a ground via the first and the second nodes of the shunt voltage regulator to regulate a flow of current from the LED driver dimming line based on the reference voltage supplied via the voltage divider.
2. The apparatus of claim 1 wherein second resistance source comprises:
a plurality of discrete resistors, each of the discrete resistors of the plurality of discrete resistors having a respective associated voltage drop thereacross; and
wherein the at least one switch is operable to selectively electrically couple the discrete resistors into the voltage divider one at a time.
3. The apparatus of claim 2 wherein the at least one switch has a total number of states equal to an integer value of n and a total number of the plurality of discrete resistors is equal to the integer value of n.
4. The apparatus of claim 3 wherein for each of the discrete resistors of the plurality of discrete resistors, the respective voltage drop thereacross is different from the respective associated voltage drop across each of other ones of the discrete resistors of the plurality of discrete resistors.
5. The apparatus of claim 4 wherein for each successive state of the total number of states of the at least one switch, the at least one switch electrically couples a respective one of the discrete resistors into the voltage divider, where each successive one of the discrete resistors coupled into the voltage divider has a respective value of resistance that is successively higher than a respective value of resistance of an immediately previous one of the discrete resistors.
6. The apparatus of claim 4 wherein the at least one switch has eight states and the plurality of discrete resistors includes eight discrete resistors.
7. The apparatus of claim 6 wherein the plurality of resistors have respective values of resistance of: approximately 100 Ohms, approximately 14.4 KOhms, approximately 16.5 KOhms, approximately 19.6 KOhms, approximately 24.9 KOhms, approximately 34.4 KOhms, approximately 54.9 KOhms and approximately 130 KOhms within plus or minus 10% of a nominal one of the values of resistance.
8. The apparatus of claim 1 wherein the second resistance source comprises a potentiometer having a variable resistance in a specified range of resistances, and the at least one switch is operable to adjust the potentiometer.
9. The apparatus of claim 8 , further comprising:
a third resistance source, where the first resistance source is on a first side of the voltage divider and the third resistance source is on a second side of the voltage divider, the first and the second resistance sources having respective values of resistance sufficient to provide a bias current when the at least one switch is set to a maximum dimming setting in which one or more solid-state light sources are driven to produce light.
10. The apparatus of claim 8 wherein the potentiometer is operable to provide a continuously variable resistance in the specified range of resistances.
11. The apparatus of claim 1 wherein the at least one switch is a mechanical selector switch.
12. The apparatus of claim 1 wherein the at least one switch is a rotary mechanical selector switch.
13. The apparatus of claim 1 , further comprising:
a housing having an interior and an exterior, the first resistance source, the second resistance source and the shunt voltage regulator housed in the interior of the housing, and wherein the at least one switch is physically engageable from an exterior of the housing either with or without a tool.
14. The apparatus of claim 1 , further comprising:
a housing having an interior and an exterior, the first resistance source, the second resistance source and the shunt voltage regulator are all housed in the interior of the housing, and wherein the at least one switch includes a knob that extends into the exterior from the housing and is physically engageable from the exterior of the housing without a tool.
15. The apparatus of claim 1 wherein the at least one switch is operable to set a desired dimming level of a luminaire.
16. The apparatus of claim 1 , further comprising:
a first connector to mechanically and electrically couple to an LED driver.
17. The apparatus of claim 16 wherein the first connector takes the form of a two-wire configuration that electrically couples only a dimming line and a ground line to the LED driver and does not have any auxiliary power supply line.
18. The apparatus of claim 17 wherein the first connector takes the form of a three-wire configuration that electrically couples a dimming line, a ground line, and auxiliary power supply line from the LED driver.
19. The apparatus of claim 17 , further comprising:
a second connector to mechanically and electrically couple to an accessory.
20. The apparatus of claim 19 wherein the accessory is a low power photocontrol.
21. The apparatus of claim 1 , further comprising:
a plurality of light emitting diodes and wherein the apparatus takes the form of a luminaire.
22. The apparatus of claim 1 wherein the apparatus is physically and electrically coupleable to a luminaire that comprises a plurality of light emitting diodes and the apparatus is operable to adjust an output of the plurality of light emitting diodes of the luminaire.