Detecting LED colors

S

sedeap

Senior Member
OK...
Picaxe attached to an LDR or PhotoTransistor can detect presence of light an even How much light... but... how can I detect the color of that light?

Some sealed meter, have two multicolor LED to show status and functions... even a beacon flash "I'm alive" kind of... but the real problem is they use different color to show status, so... if blink is green, its ok, and if blink red isn't...
Same to other LED, if remains amber, status 1, but if turn to blue, status 2, and if becomes green is status 3 and so on and on...
Worst part of this is.... (yeah you get it) I need to interface that damn thing cuz they install it in a very uncomfy spot...

So... (the million euro question here)
How can I achieve that ?
Any suggestions?
( suicide is NOT an option... lol)

C.U Pals...

.:D
 
D

Dippy

Moderator
I don't know how complicated you want, so how about separate sensors with colour filter film over each?
Then each sensor is selectively sensitive to a colour.
Or you could, if feeling enthusiastic, use an RGB sensor like the type made by TAOS TCS3200.

Some sweet wrappers are good filters - and you can munch on the contents whilst designing. Perfect!
Cadbury's Quality Street are particularly good. Yummy.:rolleyes:
 
Buzby

Buzby

Senior Member
With a single sensor wired to an analogue input, there should be a measurable difference when illuminated with different colours.
Have a look at the spectral response chart for some different sensors, or just play around with a few.

ExampleSpectralResponse.png

Cheers,

Buzby
 
S

sedeap

Senior Member
Old School Tech

Ok...
@Dippy
You really make my day... lol...
munching sweets probably get 20 pounds in body and still try to achieve perfect calibration.
but is the most tempting solution-path... LOL...
(here we have a brand "yummy" of jelly candies, taste like silicone, but kids love it... lol...)

@e
nice start... but... here can't grab one of those (i love to hack devices... lol)
(due restrictions in customs and heavy taxes in some electronics gadgets purchased overseas)
15 years of a government that really sucks... in every aspect.
(sorry 4 the OT Phrase)

@Buzby
It's interesting that approach, but I think that will be tricky due a short term "blink" and the ability of picaxe to read it...
but worth a try, like Dippy's candy-wrapper filters...

:rolleyes:

Meanwhile, because I'm a Old School tech, I start doing like Cambridge University, and put a little webcam towards the meter

C.U. Pals
 
P

Paix

Senior Member
I think with the price of the device, that customs duty would be the least of your problems.

Dynamic calibration of anything but the OK green seems like it might stretch your patience. Cheap method, put the bag of silicon gusanitos next to the meter and pop a stool there for the kids to eat the gusanitos (worms) and tell you if anything is wrong. Cheaper than a TV for the kids or a webcam for you and maybe as educational as the cartoons!

Spongebob Squarepants, eat your heart out!

Put a box in with the meter and tell the kids that it's a space ship, they will play there for hours!
 
E

eclectic

Moderator
A low-possibility suggestion?

Different coloured clear LED's,
wired "in reverse" as detectors,
and used with ReadADC?

e
e
 
A

AllyCat

Senior Member
Hi,

Yes, it is said that LEDs of a particular colour can also act as photosensors for a similar colour. But beware that the generated photelectric voltage and current are quite small. Photodiodes and Phototransistors more normally use (reverse) leakage current (so a tinted package might be better).

There are some interesting links in this fairly recent thread which you might find useful.

Cheers, Alan.
 
S

sedeap

Senior Member
RGB Detector

@Paix
Yep... pricey device to hack it...
Kids maybe like go next to meter for candies... but caldron room isn't right place for them.
(but I try to put them to watch the webcan and "read" the patterns of the meter... better than watching cartoons... LOL )

@e
That's not bad idea... I will try it aside of Dippy's filtered sensors...

@Alan
Agree... as I say above... I will try

@JimPerry
Nice find jim... Thanks... I will order a couple of those to play with...

I think This http://atlas-scientific.com/product_pages/sensors/env-rgb.html maybe make the thing easier... and not pricey...

C.U.Pals
:eek:
 
Buzby

Buzby

Senior Member
Those colour sensors that Jim posted are going to be a bit of a challenge with a PICAXE, especially if you need to detetect the colour of a very short pulse.

The devices are 'Intensity-to-Frequency' convertors, take a look at the datasheet for the TCS3200 chip they are using.

Cheers,

Buzby

EDIT : The Atlas device takes 620mS to make a reading. Again, not much use when looking for a short pulse.
 
Buzby

Buzby

Senior Member
Hi Jim,

That post shows how to detected the colour of an object by illuminating it, then measuring the reflected light.
The OP is trying to detect the colour of a pulse from an LED.

All the colour sensors I've looked at have either frequency outputs, or I2C, SPI etc.

I still think using the relative sensisitivity of a single sensor is worth a try.

Cheers,

Buzby
 
D

Dippy

Moderator
That could work as long as the ambient is known. I don't know the OP's setup, so if ambient is variable then there could be problems.
I also don't know the relative intensities of the LEDs. If, sod's law being what it is, the intenisty * sensitivty is fairly equal then it could be ambiguous.
Without more info it's tricky.

Not wishing to empty other people's wallets TAOS used to make Intensity-V devices with built-in RGB filters. You could buy separate R,G,B variants. But they may be hard to source.
Buzby's suggestion is certainly easy for OP to try and may be fine.
 
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