Effects of Daylight Harvesting onElectronic Lighting Control Copyright © 2004 Joshua Scot Lester - Calvin College Engineering 315 Control Systems

© 2004, Joshua S. Lester 2

Triac Dimming

Vb

Vm

sin e

CR

sin

1 2

C2 R

2

where tan1 CR

Vcis the capacitor voltage

Vbis the breakover voltage

Zero-crossingA dimmer controls the power to the load through a solid state switch or triac. The triac is synchronized to the AC line through signals obtained at zero crossings

Triac-firingThe zero crossing signals are then used to fire the triac to give the correct dimmed waveform

© 2004, Joshua S. Lester 3

Daylight Harvesting System

[10] Closed-Loop Lighting Control System Diagram

© 2004, Joshua S. Lester 4

Photosensor vs. Photocell

photocell the light sensitive component inside the photosensor.

Photosensoran entire product including the housing, optics, electronics, and the photocell.

© 2004, Joshua S. Lester 5

Spectral and Spatial Response

[1] Closed-loop lighting control block diagram

© 2004, Joshua S. Lester 6

Input characterization Spatial response

The input to a photosensor is optical radiation infrared (IR) ultraviolet (UV) radiation

For lighting control it is measuring the distribution of luminaire intensity

[2] Photosensor Spatial Response Spectrum

[2] Photosensor Spatial Response Spectrum

© 2004, Joshua S. Lester 7

Input characterization Spectral response

sensitivity to optical radiation of different wavelengths

[3] Spectral Response Chart

[4] Optical Radiation Chart

© 2004, Joshua S. Lester 8

Open-loop Proportional Control

Open-loop control has one adjustable parameter

the constant of proportion between the control voltage and the optical signal

[5] Savings in the Spotlight [7] Open-loop control

© 2004, Joshua S. Lester 9

Closed-loop Proportional Control

2 ADJUSTABLE PARAMETERS:

1. SLOPE ( open-loop response curve )2. OFFSET ( commissioning )

Closed-loop control algorithma.k.a "sliding set point control"

[5] Savings in the Spotlight [8] Closed-loop control

© 2004, Joshua S. Lester 10

Control AlgorithmClosed-loop proportional control

The ceiling illuminance is 100 lux with no daylight present (from the 5:1 work-plane: ceiling ratio)

Desired work-plane illuminance 500 lux

Daylight enters the room and adds 250 lux

Rate of dimming was set to -0.25% per lux

0.25% per lux X 250 lux = 62.5%

This sets the luminaire light output to:

100 lux - (62.5% X 100 lux) = 37.5 lux.

The total ceiling illuminance is now

37.5 lux + 250 lux = 287.5 lux.

[9] CL Example

© 2004, Joshua S. Lester 11

Sample of Daylight Harvest Control

[6] Simulation of lighting levels in modeled room.

© 2004, Joshua S. Lester 12

Personal controls

http://www.vantagecontrols.com/

© 2004, Joshua S. Lester 13

Big Picture

© 2004, Joshua S. Lester 14

References

I. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/controlMostImportantGraphic.jpgRensselaer Polytechnic Institute, Troy, NY 12180 USA

II. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/polar.aspRensselaer Polytechnic Institute, Troy, NY 12180 USA

III. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/spectralgraph.jpgRensselaer Polytechnic Institute, Troy, NY 12180 USA

IV. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/small5.jpg Rensselaer Polytechnic Institute, Troy, NY 12180 USA

V. Savings in the Spotlight By John L. Fetters, published June ’02

VI. http://eetd.lbl.gov/btp/pub/designguide/section8.pdf

VII. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/openLoopProp.jpg Rensselaer Polytechnic Institute, Troy, NY 12180 USA

VIII. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/closedLoopProp.jpg Rensselaer Polytechnic Institute, Troy, NY 12180 USA

IX. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/closedLoopExample.jpg Rensselaer Polytechnic Institute, Troy, NY 12180 USA

X. http://www.lrc.rpi.edu/programs/nlpip/tutorials/photosensors/img/photosensors%20fig.jpg Rensselaer Polytechnic Institute, Troy, NY 12180 USA