Light Meter Circuit Help

[heberjm8]

Hello. I’m hoping I can get some much needed help at this forum with the design of a circuit. I’m designing an ambient light sensor with a digital display showing the amount of lux detected. I’ve done research on the internet for possible circuit help but with no luck. If someone would respond with thoughts or possible circuit ideas I would GREATLY appreciate it. THANK YOU SO MUCH.

 

[ben7]

Hello. I’m hoping I can get some much needed help at this forum with the design of a circuit. I’m designing an ambient light sensor with a digital display showing the amount of lux detected. I’ve done research on the internet for possible circuit help but with no luck. If someone would respond with thoughts or possible circuit ideas I would GREATLY appreciate it. THANK YOU SO MUCH.

Hmm, I don't know how to make a circuit that tells you lumens but I could make a simple led bar graph light reader. Maybe the bargraph light meter circuit could be calibrated somehow.

 

[Reloadron]

Designing and building a basic lux meter circuit isn't a problem as there are plenty of ideas on the internet like this one or maybe this information. Then we have this link also which includes a schematic. The trick becomes the accurate calibration of the instrument so the displayed numbers actually mean something. A Google of Lux Calibration will yield more results.

Additionally posting the same question multiple times in different internal forums will not get you faster or quicker answers but will confuse people who may try to assist you.

Ron

 

[heberjm8]

ben7,
Thank you so much for responding. I have to use a digital display to show the lux. Any ideas? Thanks.

 

[Dragon Tamer]

So you can't use LED's in your display? What are you supposed to use, magic? How about an LCD, VFT, Tube? Why don't you just use an ADC with the display driver built in?

 

[heberjm8]

Sorry about the multiple posts. I just wasn't sure of the best area to post in.

I'm able to use a PIC chip for this project.

ben7,
Thank you so much for responding. I can use leds in the project. My mistake. Maybe like a 5 or 6 digit display for the lux. I see lux meters are normally maxed out at 20k, 50k, or 100k lux.

 

[Dragon Tamer]

You could connect the photo sensor to an LM3914 to make a cheap display. I think that they even have a schematic in the data sheet for a light meter using a photo-diode. I know it's in the data sheet for the LM3915.

 

[Reloadron]

Something you can try, if you look at the last link I posted they mention calibration. The way they seem to get in the ballpark is using the data sheet for the photo diode they use. Making a circuit to respond with an analog voltage to run into a digital display isn't difficult. The trick becomes getting the numbers to accurately display the lux equivalent of the light striking the photo diode. Also, as Dragon Tamer points out, an analog voltage from a photo diode could drine an LM3914 and provide a linear dot or bar LED display.

Ron