Read LEDs of a system under test?

[ebriaug]

Hi,

I have a system (with real LEDs, i.e. not inside labview) that that can have the following color states for LEDs:

Red, green, yellow and none.

it should also be possible to detect a blink frequency up to 2 Hz.

Is there any equimpent for this? I know it can be done with IMAQ and cameras but is there any other measurement way? With opto components?

/Regards

[EvenDeejay]

I would have measured the LED voltage, since it will be different for different colors. Correct me if I'm wrong though.

[smercurio_fc]

I would agree that simply measuring the voltage should be an easy way to determine if the LED is on and/or blinking. Your frequency of blinking is quite low, so you won't need high-speed data acquisition. As for the varying voltages, that should not be the case. It's not clear from your post whether you're dealing with different LEDs, or multi-color LEDs. However, even with multi-colored LEDs, they have multiple leads to activate the different colors, not different voltages.

[PhillipBrooks]

A quick Google search turned up this video that shows LED testing using opto components.

Bookmarking this for my own possible use.

http://www.youtube.com/watch?v=BMfl2mrPI2s

Product web site: http://www.feasa.ie/

[PhillipBrooks]

Also found this...

http://www.optomisticproducts.com/

[johnsold]

LEDs themselves can be used as color-selective photodiodes.  If you can get the same type of LED used in the device, couple it optically to the LED being tested, connect it as two or three photodiodes*, then connect the outputs of the photodiodes to an analog input device.  Measuring the voltages out of the photodiodes should get you to the information you want.

* Two if the device has two diodes and gets three colors by having both on at the same time, or three if it has three diodes.

Lynn

[ebriaug]

Here comes some late answers:

1. The LEDs are all built in into the system and therefore not possible/resonable to connect probes for voltage measurement.

2. Its multi colored LEDs attached on the PCB (i.e. really small connections)  with green, red and yellow (all max 2 Hz).

Also the system contains quite a few LEDs of this kind (say about 50) so i am leaning towards an camera solution where all LEDs can be read. Can it be done with a webcam?

Any inputs there?

[sebster]

http://www.feasa.ie/led_analyser/led_analyser_overview.htm