Neggo44
Posts: 2
Joined: Fri Mar 04, 2016 10:48 am

Light Flick measurement

Fri Mar 04, 2016 2:41 pm

Hello,

this is my first post, hope I post on the right area

I'm interested in to develop a light flick measurement instrument,
some have any idea where can be found a similar project or how start?

I need a opto component to read light waves,

for instance, a LED that work directly at 220Vac that produces a 50 - 60 Hz flick effect

thank you for your help

Neggo44

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liudr
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Re: Light Flick measurement

Fri Mar 04, 2016 7:10 pm

Are you sure that an LED will flicker or are you wondering whether it will flicker? My suspicion is that it doesn't flicker. Or maybe it does, if it is dim-able.
Arduino data loggers, user interface, printed circuit board designer since 2009, RPI 3B 2B 2B Zero Jessie, assembly/C/C++/java/python programmer since the 80's

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GTR2Fan
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Re: Light Flick measurement

Fri Mar 04, 2016 7:15 pm

Neggo44 wrote:for instance, a LED that work directly at 220Vac that produces a 50 - 60 Hz flick effect
An LED connected directly to 220V AC will produce one very bright flash as it explodes.
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boyoh
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Re: Light Flick measurement

Fri Mar 04, 2016 11:12 pm

First DO NOT CONNECT A LED DIRECTLY TO 240vac . If you want to use ac , use a step down transformer
to a voltage that will satisfied a LED through a resistor.

A led as no after glow when switched off, If it did there would be no Optic Fiber signals.
If you what to check the flicker , just check the ac applied Hz
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

Neggo44
Posts: 2
Joined: Fri Mar 04, 2016 10:48 am

Light Flick measurement

Mon Mar 07, 2016 8:58 am

Hello,

Thank you for your comments. The LED don’t work at 220Vac, I mean when the LED Systems have a low price power supply, the DC supplied by the PS is not a Vdc stable, is an unstable voltage, usually at same frequency than AC power source.
Anyway, my point is just asking about the Raspberry issue, after accept the Light flick, I attach one example,

http://www.ledsmagazine.com/articles/pr ... icker.html

my question is,

someone have any idea how to link a opto part that measure the light source with a Raspberry that register this measurements?
Thanks for your comments

Neggo44

ferg
Posts: 32
Joined: Sun Jan 31, 2016 2:42 am

Re: Light Flick measurement

Mon Mar 07, 2016 9:25 am

I'm interested in this topic but for a different application.

I have been researching avalanche photodiodes as the sensor due to high sensitivity and also some inbuilt gain. Generally they are integrated with a high pass filter (you might need low pass???) and an op amp with feedback circuit.

I am yet to get into signal levels and specific components, but the available info (at least for RPi) appears quite sparse.

boyoh
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Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: Light Flick measurement

Mon Mar 07, 2016 8:17 pm

I think you need more under standing of electronics on this project to,succeed, So back to the BreadBoard.
A understanding of fast signal generating , and detecting you will need.
Start with a very stable ,well filtered power supply ,A oscilloscope will be very handy for checking fast signals
And noise (transients, Do some research on the use of Opto electronics
A signal generator will be very handy
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

toxibunny
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Joined: Thu Aug 18, 2011 9:21 pm

Re: Light Flick measurement

Mon Mar 07, 2016 9:13 pm

http://www.raspberrypi-spy.co.uk/2012/0 ... -gpio-pin/ - this is the hardware. you'll probably have to do some tweaking with the resistor/capacitor values.

viewtopic.php?p=347830#p347830 - Joan's pigpio library can read the relevant pin up to 1 million times per second. that should be enough.

In a somewhat related post, she wrote: "I have a library which will sample the user gpios at 1MHz. At that rate it uses about 25% of the Pi's CPU for processing. You could have a callback on gpio change which just incremented a count. Start the callback and stop it a few 10s of milliseconds later. You'd then have a count of state changes over a duration."

Hope this helps.
note: I may or may not know what I'm talking about...

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