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Coupling LED to LDR

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George Herold

Jan 1, 1970
0
Hi, John:-

Didn't know about (or didn't remember, same thing I guess) those,
thanks, very interesting.

Probably too high resistance for this application, but I could see
using them. I might add them to the layout to play with them.
That is interesting. Are you sure you mean too a high resistance? It goes down to ~200 ohms or so. I thought LDR's were ~10k.

One bad thing is that it's only (approximately) linear for delta V less than 100mV, or so.

George H.
 
G

George Herold

Jan 1, 1970
0
George Herold Inscribed thus:





A very light touch into a flame will polish the end !

Thanks Baron, I'll give that a try.

George H.
 
S

Spehro Pefhany

Jan 1, 1970
0
That is interesting. Are you sure you mean too a high resistance? It goes down to ~200 ohms or so. I thought LDR's were ~10k.

Depends on how much light you shine on them. ;-)
One bad thing is that it's only (approximately) linear for delta V less than 100mV, or so.

George H.

LDRs are pretty linear if you keep the voltage across them less than a
couple hundred mV.
 
W

whit3rd

Jan 1, 1970
0
I'm prototyping a circuit with an LED-LDR photocoupler, which are
rather rare beasts these days. I've bought a bunch of LDRs... if I can
couple the light a bit better.

This will depend on the LDR sensitivity to different colors of light; have you
considered using a Day-Glo (green or red-orange) phosphor
and a UV or blue LED? LEDs with lenses are hard to get uniform
light out of, but a flat label-dot with fluorescent paint is a
good 2-pi-steradians source, regardless of how the illumination light
comes in.
 
A

Anthony Stewart

Jan 1, 1970
0
I haven't read a spec yet on what you need to detect. Distance ? size? object? speed?

Sharp/Vishay Photo Diodes are the most stable repeatable inexpensive passive Sensors. Panasonic makes a nice buffered current source Photo Detector that is CIE color corrected with > 7 orders of magnitude sensitivity.

I used to be able to detect a resistor wire passing an LED beam 1 meter across a path to an IRDA AGC Photo Receiver. I recessed both IR LED and Irda Receiver by >1cm with a 4mm hole to get a narrow aperture to block stray light. I could use multiple paths adjacent to each other using a TDM unique pattern on each path to detect any interruption of light on any path and computer the direction and speed an object was moving across the lane.
 
A

amdx

Jan 1, 1970
0
Are you color blind? I bet you have a gray car.

This is mine:

https://dl.dropboxusercontent.com/u/53724080/A3a.jpg

I'm mostly visual. I like shapes, depth, colors, light, patterns, structures,
motion, circuits.

Nothing personal John, just teasing you.
I took my daughter to a hamfest last year, she bought a little
electronics kit for her husband to assemble. I was helping him
when I realized he couldn't read some colors on the resistors,
I felt bad because I had teased him about reading the colors.
I got the meter out and showed him how to use it.
Ya got me on the cars though, I have a silver/gray truck, white car
and a white cargo van.
I did have a Blue Lexus, I let my son take that to college with him.
Can I get partial credit for that? :)
I like shapes too, especially a high waist to hip ratio.
I'd go with blue as a favorite, like the lighter blue in the Firefox Icon.
btw, I had a cherry red 66 Ford Fairlane 500 with chrome wheels,
but that was about 40 years ago. Oh, she sounded sweet!
Mikek
 
J

JW

Jan 1, 1970
0
I have this one in dark blue...

<http://www.edmunds.com/infiniti/q45/2005/?

Want to drag ? I can beat most Mustangs >:-}

The V6? Sure, if that's what you mean by "most" mustangs.
2005 q45 specs:
340HP @ 6400RPM with 333ft-lbs @ 4000RPM

The 2013 Mustang GT base model:
420HP @ 6500RPM with 390ft-lbs @ 4250RPM

The driver's skill could make a difference, though.
 
G

George Herold

Jan 1, 1970
0
Depends on how much light you shine on them. ;-)

Ahh OK... the lowest R I found on Digikey was this,
http://www.advancedphotonix.com/ap_products/pdfs/PDV-P8001.pdf
But I didn't look very hard. ~3k at 10 lux...I might guess 1 k ohm at 100 lux.. (looking at other curves.) Do you get thousands of lux from an LED?
(Groan, I hate optics intensity units! I have no feel for one lux.)

OK best way is to shine an LED at whatever LDR I happen to have here.

George H.
 
A

amdx

Jan 1, 1970
0
Is there a difference? Equally boring fake-luxury granny cars.

That was my point, the Infiniti was a look-a-like of the 8 years
older Lexus. But I think it looks better. :)
Mikek
 
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Lasse Langwadt Christensen

Jan 1, 1970
0
Den fredag den 1. november 2013 01.32.46 UTC+1 skrev [email protected]:
So does a Mustang. My wife's '14 is 4580lbs, according to the door

label.

that is probably the max allowed weight including passengers and cargo

-Lasse
 
A

amdx

Jan 1, 1970
0
Why would anybody buy a car that's not a hatchback?
Cause I have pickup truck.
But John, that's what makes a horse race.
To each their own.
Unless it's regarding health insurance, then it's Obama's choice.
 
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