Didn't see a post about this with the search tool, but found a similar but outdated thread that only touches the subject.
I want to make an LED array get brighter when the photoresistor sees light, and turn off when there is no light. However, I'd like to have the LED's dim partially in partial light. So not an on/off circuit, but rather a linear dimming circuit for the LEDs that mimics the light seen by the photoresistor.
The project goal: Make LED lighting behind my 55" flatscreen tv that is as bright the image on the screen. This lighting effect is supposed to reduce eye strain when watching movies in a completely dark room.
There's a spot on the front corner of the TV stand that receives all the light of the tv screen that I think would be a great location for the photoresistor to get a representative sample of the current scene's brightness.
A static setup would work, BUT in bright scenes the backlighting would be unseen, and in very dark scenes the backlighting would be too bright.
I want to make something that uses about 20 white LEDs (3.3v 20mA) and on a completely black scene the LEDs are either full off or nearly off, and on a bright scene the LEDs are full on. And linear in-between of course.
The tool here: http://led.linear1.org/led.wiz tells me that with 12V (i have a few spare wall warts) I can use pairs of LEDs in series with a 120ohm resistor, and 10 pairs of this grouping gives me the 20 LED array driven by 12V.
Something tells me that supplying the array with 0V-12V is not equal to 0%-100% LED output, as least not in a linear fashion.... I figure LED's will drop off to darkness at about half their typical voltage. But figuring is figuring... I need to make this array and vary the voltage to see where the actual 0% LED output occurs.
Before I do that, and while I gather supplies, I wanted to get help and input on this project. I think I have the physical and mechnicals thought out enough... I just can't figure out how to make the dimmer part that works with a photoresistor. I am mostly inexperienced with transistors, so I don't know if that is the answer. Can a transistor make a varied power output from a varied photoresistor input?!?? If not a transistor, please point me in the right direction.
Until I get back with my measurements let's say I wanted complete darkness to supply 6V and complete brightness supply 12V. Any ideas??
Thanks in advance for your help. I plan on posting images or videos of the linear backlighting in action if it works out well.
I want to make an LED array get brighter when the photoresistor sees light, and turn off when there is no light. However, I'd like to have the LED's dim partially in partial light. So not an on/off circuit, but rather a linear dimming circuit for the LEDs that mimics the light seen by the photoresistor.
The project goal: Make LED lighting behind my 55" flatscreen tv that is as bright the image on the screen. This lighting effect is supposed to reduce eye strain when watching movies in a completely dark room.
There's a spot on the front corner of the TV stand that receives all the light of the tv screen that I think would be a great location for the photoresistor to get a representative sample of the current scene's brightness.
A static setup would work, BUT in bright scenes the backlighting would be unseen, and in very dark scenes the backlighting would be too bright.
I want to make something that uses about 20 white LEDs (3.3v 20mA) and on a completely black scene the LEDs are either full off or nearly off, and on a bright scene the LEDs are full on. And linear in-between of course.
The tool here: http://led.linear1.org/led.wiz tells me that with 12V (i have a few spare wall warts) I can use pairs of LEDs in series with a 120ohm resistor, and 10 pairs of this grouping gives me the 20 LED array driven by 12V.
Something tells me that supplying the array with 0V-12V is not equal to 0%-100% LED output, as least not in a linear fashion.... I figure LED's will drop off to darkness at about half their typical voltage. But figuring is figuring... I need to make this array and vary the voltage to see where the actual 0% LED output occurs.
Before I do that, and while I gather supplies, I wanted to get help and input on this project. I think I have the physical and mechnicals thought out enough... I just can't figure out how to make the dimmer part that works with a photoresistor. I am mostly inexperienced with transistors, so I don't know if that is the answer. Can a transistor make a varied power output from a varied photoresistor input?!?? If not a transistor, please point me in the right direction.
Until I get back with my measurements let's say I wanted complete darkness to supply 6V and complete brightness supply 12V. Any ideas??
Thanks in advance for your help. I plan on posting images or videos of the linear backlighting in action if it works out well.