As far as a tool to measure this, it's called an oscilloscope and has existed for decades. You can connect a photodiode directly to an oscilloscope with no additional hardware needed at all if you're just looking at mains frequency flicker. I've been tempted to pick up one of those $25 toy DSOs specifically for this purpose.
As far as a tool to measure this, it's called an oscilloscope and has existed for decades. You can connect a photodiode directly to an oscilloscope with no additional hardware needed at all if you're just looking at mains frequency flicker. I've been tempted to pick up one of those $25 toy DSOs specifically for this purpose.
Actually I made something like that. I used a solar cell from solar "recharged" key-chain flashlight (recharged witch quote marks because inside was only two 2016 batteries and real solar cell not connected to anything) with some resistor laying around as a load. Connected both sides to DSO150 and you got portable flicker and pwm frequency meter. Works on mains led lamps, works on torches (if you want to know frequency and duty cycle on lower power settings). Obviously has some limitations but for this purpose is great.
As far as a tool to measure this, it's called an oscilloscope and has existed for decades. You can connect a photodiode directly to an oscilloscope with no additional hardware needed at all if you're just looking at mains frequency flicker. I've been tempted to pick up one of those $25 toy DSOs specifically for this purpose.
Actually I made something like that. I used a solar cell from solar "recharged" key-chain flashlight (recharged witch quote marks because inside was only two 2016 batteries and real solar cell not connected to anything) with some resistor laying around as a load. Connected both sides to DSO150 and you got portable flicker and pwm frequency meter. Works on mains led lamps, works on torches (if you want to know frequency and duty cycle on lower power settings). Obviously has some limitations but for this purpose is great.
as I understand it, digital flat screens do not flicker.
A test instrument to measure the flicker of lighting would be handy to have. Anybody care to create one?
I attached a photo of how I measured the duty, with a photodiode attached to a handheld oscilloscope.
It seems that EN12464 has banned anything with CFD >50%...so thats all PWM'd LEDs at 100Hz, which evil kindly confirms in effect.
You probably need a load resistor across the photodiode to discharge the scope's and PD's capacitance to improve the fall times. For only 100Hz 50k to 5k would do.
I attached a photo of how I measured the duty, with a photodiode attached to a handheld oscilloscope.
You probably need a load resistor across the photodiode to discharge the scope's and PD's capacitance to improve the fall times. For only 100Hz 50k to 5k would do.
I don't think photocells are fast enough to see an accurate real shape of even 100Hz flicker, a photo transistor could be ~50 X faster, and a photodiode ~50 X faster again.
Regarding photocells, it's the same story as photodiodes. I just run a test with a PWMed LED captured with a 1"x6" solar panel and loading it with a 5k-10k resistor allowed you to see up to 2kHz with relatively square edges.
Solar cells are HUGE though compared to photodiodes, as far as I know, it's the large capacitance that limits their bandwidth.
Yes that's what I was thinking, maybe they're OK for curved ~100Hz light shapes, I don't know anything about how linear they'd be.
I wish someone else would try some high speed linear light experiments I've done enough! Sometimes we see an op amp TIA but don't get to see it's response to a square wave light input.
https://www.analog.com/designtools/en/photodiode/