Lux measuring from the sealing

[Baggal]

Hey everyone I have to build a device witch I can install to the sealing and that tells me how bright it is on the floor. I thought of a normal Photodiode witch I shielded from the sides and pointed towards the floor but the problem is that depending to the surface I point my sensor on I get different reflections. Has anyone an idea how to avoid that problem? Or is there an existing Sensor?

Thanks a lot

Greets Baggal

 

[Baggal]

sorry for my English i mean ceiling

 

[VEBill]

Ref.

http://www.handprint.com/HP/WCL/color3.html#photounits

Aim your sensor up, or calibrate for the semi-reflective surface of the floor.

 

[IRstuff]

Generally, light meters have a diffuser over the detector to produce a more repeatable measurement:

http://www.amazon.com/Sekonic-Corpo...=sr_1_4?s=photo&ie=UTF8&qid=1349793013&sr=1-4

You should not point to the flooring unless the sensor is well calibrated for that. The reflectivity of the flooring will vary depending on material and wear/cleaniness

TTFN
faq731-376

 

[mcgyvr]

buy and put a lux meter sitting on the ground facing up..
Whats the reason for the test?

 

[Baggal]

Thanks for the reply’s

I have to develop an illuminate System for an open-plan office. And it should be a bit intelligent so only turn on the light if someone is around and it's not light enough. Now the plan is, that we only have to install new lamps, so with all the electronics included means no extra sensor-farms… that's why I have to measure how light it is from the ceiling.

 

[IRstuff]

I still don't get it; how is measuring the light level going to help you determine whether someone is present? Usually, such lights use motion sensors to detect people. Lighting level is usually done by design only, using some sort of IESNA design software.

TTFN
faq731-376

 

[Baggal]

but if my motion sensors tell me that there is someone around i need to know if the light should turn on or if it already is light enough from daylight.

 

[IRstuff]

OK, this is new information. I would then go back to the idea of using an off-the-shelf photographic light meter.

TTFN
faq731-376

 

[VEBill]

He's looking for a combination of an Occupancy Sensor plus an Ambient Light Sensor so that the light won't come on if daylight is pouring in through windows or skylights.

Get a wide angle sensor, install it on a ceiling or wall, aim it down, and adjust to taste. It's not going to be that accurate that natural variations are going to be the cause of complaints. The entire concept might be...

You'll need hysteresis. And probably timers. Perhaps outdoor sensors. And over-rides.

 

[davidbeach]

And, it probably all exists off the shelf anyway.

 

[nesp]

As David pointed out, it exists already. It is daylight harvesting and it combine both presence and light detectors. Osram, Helvers and Philips of this world have them.

 

[Baggal]

it is true this already exists, but the problem with most of these lamps is that there motion detection isn't fine enough so if i want to use it at a office and the person isn't really moving the light goes off. but you are probably right to just pimp out a existing off the shelf product.

 

[IRstuff]

Motion sensing is a wholly different topic than light level sensing. Regardless of what one uses for any sort of detection, there is a fine line between detection and false alarms. And when someone is simply stopped moving around, there are few cheap solutions to detecting their presence, although there are supposedly smart phone apps that can do image analysis to determine respiration motion. Alternately, the so-called smart phone proximity sensor technology could be applied to each chair in the room. In either case, the cost of the components and wiring may make them unfeasible for most applications.

TTFN
faq731-376