Design Article
Intelligent lighting controller measures ambient light and tracks time
Marko Kannisto and Philip Simpson, Maxim Integrated Products, Inc.
3/9/2012 10:43 AM EST
System part lists
The controller PCB and ALS PCB part lists are shown in Table 1 and Table 2.
Next: Software block diagram
The controller PCB and ALS PCB part lists are shown in Table 1 and Table 2.
Table 1: Controller PCB part list
Table 2: ALS PCB part list
Using the System
The system is shown mounted into an enclosure in Figure 11.
Using the system is fairly simple. With the SET button, a user can define these parameters in following order:
- Current hour and minute
- Ambient light lux-level threshold (default is 2 lux )
- Light turn-off time at the evening
- Light turn-on time in the morning
The turn off/on times at the evening and in the morning do not have to be set. If not set, then the luminaire will be switched on when ambient light crosses the preset lux-level threshold at dark; it will be switched off when ambient light rises above that threshold. In this mode, the time information from the RTC is not processed.
Programmed information can be read by pressing the SET button for less than 1 second. The system will then display the hour, minute, ambient lux-level threshold, light turn-off time, and light turn-on time in that order.
If a user wants to change the programmed parameters or wants to adjust the time, then press the SET button for longer than 2s. Parameters can then be set one at a time in the same order as above. When a parameter is to be programmed, press the SET button longer than 2s so the parameter can be recorded. Same procedure is done for all parameters.
When all parameters are programmed, the system will show them one at a time so the user can verify that everything is stored correctly.
Table 2: ALS PCB part list
Using the System
The system is shown mounted into an enclosure in Figure 11.
Figure 11: System mounted into enclosure. Photo courtesy of Marko Kannisto
Using the system is fairly simple. With the SET button, a user can define these parameters in following order:
- Current hour and minute
- Ambient light lux-level threshold (default is 2 lux )
- Light turn-off time at the evening
- Light turn-on time in the morning
The turn off/on times at the evening and in the morning do not have to be set. If not set, then the luminaire will be switched on when ambient light crosses the preset lux-level threshold at dark; it will be switched off when ambient light rises above that threshold. In this mode, the time information from the RTC is not processed.
Programmed information can be read by pressing the SET button for less than 1 second. The system will then display the hour, minute, ambient lux-level threshold, light turn-off time, and light turn-on time in that order.
If a user wants to change the programmed parameters or wants to adjust the time, then press the SET button for longer than 2s. Parameters can then be set one at a time in the same order as above. When a parameter is to be programmed, press the SET button longer than 2s so the parameter can be recorded. Same procedure is done for all parameters.
When all parameters are programmed, the system will show them one at a time so the user can verify that everything is stored correctly.
Next: Software block diagram
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docdivakar
3/14/2012 10:17 AM EDT
Seems like the value added from a utility perspective is little in comparison to many solutions that already exist there (many solar lights for gardens and walkways switch on automatically, albeit without a real time clock). If cost of adding ALS changes the lighting solution cost, it may not be worth it. I can get a timer for multiple circuits and control on-off times (the XMas tree controllers for example).
MP Divakar
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wb9ddf
3/15/2012 2:51 PM EDT
About 10 or 12 years ago I built a lighting control system with similar function for an office building I own. I used a timer and photocell from the local home improvement store. The photocell was wired in series with the timer switch contacts. The result is that the lights come on at sunset, shut off at 11:00pm, come on at 5:00am and shut off again at sunrise. The clock is mechanical so it is adjusted the old fashioned way and the photocell sensitivity is adjusted with a little black tape partially blocking the sensor. Not as sophisticated as your micro-controller but it has worked for years with little maintenance other than new light bulbs and resetting the clock after a power failure.
Fred Johnson
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docdivakar
3/16/2012 3:08 AM EDT
@wb9ddf: thank you for reinforcing my point with more detailed explanation. To be fair to the authors, there may be some value-added uses cases (perhaps industrial ones) in controlling lux-level threshold but its case hasn't been made adequately in the article.
MP Divakar
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Dr DSP
3/19/2012 12:15 PM EDT
Seems like connection with the security system might be a more important feature and where some digital control/sensing would be useful.
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anne-francoise.pele
7/16/2012 11:25 AM EDT
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