minimum LED flicker rate to prevent seizures

[mik3ca]

I have a project in which the RGB LEDs are on the same circuit board as Phototransistors. The Phototransistors are able to detect light from the RGB LEDs while they are on, but I want the LEDs on as often as possible.

One idea I thought of was to turn the LEDs off to create darkness while detecting the status from the phototransistor then after the detection, turn the LEDs back on. I want to make the LED off time as small as possible.

I also want sensing of the phototransistor to be done at least 5x a second. and I want the phototransistor to be able to detect about 2 bytes of information.

In order to prevent seizures, what frequencies should I watch out for? and is it better to make the LED flicker faster or flicker slower? and what kind of duty cycle is best for seizure prevention?

 

[alec_t]

As far as I recall (but you should verify this) the critical frequency is around 7Hz for epileptic seizures, but presumably varies among individuals.

 

[jpanhalt]

In the US, there is a regulation suggesting the number is 2 Hz (https://en.wikipedia.org/wiki/Photosensitive_epilepsy ).

Edit: Here's another that sets the lower limit at 3 Hz, so 2 Hz gives a margin of safety: https://www.epilepsysociety.org.uk/photosensitive-epilepsy#.Wg7ORVVKvu8

 

[alec_t]

I think I'd rely on the figures in that second link. So, 2Hz-60Hz covers it for the majority of susceptible people.

 

[Diver300]

If you are expecting these lights to be visible, anything below 30 Hz will be annoying to nearly everyone. 100 Hz will be visible and annoying to some people, and you have to go beyond 1 kHz for the flicker not to be visible to more than a few people, and even for them it will only if they look for it.

 

[jpanhalt]

If you are expecting these lights to be visible, anything below 30 Hz will be annoying to nearly everyone. 100 Hz will be visible and annoying to some people, and you have to go beyond 1 kHz for the flicker not to be visible to more than a few people, and even for them it will only if they look for it.

I believe flicker is more easy perceived with peripheral vision than when you look directly at it. Call it evolution, if you will.