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Strobing GI that gives headaches/nausea to only a few people?

David_Vi

David_Vi

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At the Pinball Office a year or two ago now there was a Williams solid state called Pokerino, it had LEDs in the GI.

Whenever I played it I would get a headache and symptoms similar to car sickness for a few hours afterwards (depending on how long I'd played it).

To the naked eye the strobing is barely noticeable, and sometimes you can't see it at all. But once the silver ball is moving it looks as if the ball is moving in slow motion.

The thing is it only seemed to be me who suffered or noticed it.

I noticed the exact same thing with a game at PBR and a friend's place recently. I stupidly played the PBR one and then felt awful for a couple hours.

It's absolutely horrible. I fear being drawn on those games in comps or finals, what would I do? I can only think for my own health I'd have to plunge my balls and forfeit.

Has anyone else encountered this?
The majority surely don't see it or suffer from it, but there must be others.

What causes it? Is it an issue with the game? Or cheap LEDs?

The reason I thought of it today was I put some led strips into one of our games and they did the exact same thing. I later twigged that GI power is AC and most LEDs are for DC, but include a bridge rectifier to switch to DC. I made a bridge rectifier with some diodes and the LED strips stopped flickering.

I thought most pinball LEDs have bridge rectifiers included, but maybe there's some older or cheaper ones that don't and they are in a few games?
 
Blink really fast and try to synchronise your blinking with the led flicker.

I've definitely seen the effect you mention, seeing the ball movement as a series of static images, it hasn't affected me though, are you photosensitive? Maybe try sunglasses?
 
I think it may be down to the GI circuit being AC power and LEDs are designed for DC power, so the LEDS will only be lit when the AC power is in the positive part of the cycle and above the voltage to "light" the LED, then when its in the negative phase the LED acts like a Diode blocking the flow through.

I not 100% but I think you can get LEDs with a capacitor built in to keep the LEDs light while the AC circuit is in the negative phase to try and smooth out the flicker.
 
Fantazia2 said:
I think it may be down to the GI circuit being AC power and LEDs are designed for DC power, so the LEDS will only be lit when the AC power is in the positive part of the cycle and above the voltage to "light" the LED, then when its in the negative phase the LED acts like a Diode blocking the flow through.

I not 100% but I think you can get LEDs with a capacitor built in to keep the LEDs light while the AC circuit is in the negative phase to try and smooth out the flicker.
Click to expand...

I mentioned this in the post, most pinball LEDs don't have these issues. I've only seen it on 3 or 4 different games in the last 5 years so it's not common at all which makes me wonder if something else is happening. Unless there's some rare LEDs that have this issue that only a few people have used.
 
Althought you could just be more susceptible to the strobing effect, have heard about that before for DLP projectors that use a rotating colour wheel, some people can see a rainbow effect on the projection screen and others cant detect it.
 
Quoted from Pinside -

The GI circuit runs 6.3 volts AC at 60 HZ, so any LED bulbs in the GI circuit at full brightness will spend 1/120th of a second illuminated and 1/120th of a second turned-off. It is similar for all other circuits that use lamps because they were all intended to use incandescent bulbs (and thus use alternating current).

The frequency of the AC circuit is causing your flickering because your LED bulbs are most likely nothing more than an LED with a 47 ohm resistor in-series inside the casing. This problem can only truly be solved by using a bridge rectifier and a smoothing capacitor to convert the AC current to DC current, but this can be a bit of a bear to deal with for someone who doesn't know what they are doing.

However, there are sellers that sell LED bulbs with a small capacitor that helps relieve bulb flickering. Shoot some emails to Cointaker.

Was on a thread about TZ flickering LED issues - https://pinside.com/pinball/forum/topic/led-strobing-in-slow-motion
 
My solution is to convert the AC to DC with a bridge rectifier. That's what I do in my GI Led bars. Here you can see each one has a Bridge rectifier on-board:

IMG_2181.webp

I never bothered smoothing the DC ripple with a capacitor, but that would be the next step if it's ever deemed necessary.
 
The colour of cool "blue white" LED's make me feel sick, even on peoples porch lights. I've found the sudden flash of bright LED's enough to make me worry about getting a migrane.
 
Fantazia2 said:
Quoted from Pinside -

The GI circuit runs 6.3 volts AC at 60 HZ, so any LED bulbs in the GI circuit at full brightness will spend 1/120th of a second illuminated and 1/120th of a second turned-off. It is similar for all other circuits that use lamps because they were all intended to use incandescent bulbs (and thus use alternating current).

The frequency of the AC circuit is causing your flickering because your LED bulbs are most likely nothing more than an LED with a 47 ohm resistor in-series inside the casing. This problem can only truly be solved by using a bridge rectifier and a smoothing capacitor to convert the AC current to DC current, but this can be a bit of a bear to deal with for someone who doesn't know what they are doing.

However, there are sellers that sell LED bulbs with a small capacitor that helps relieve bulb flickering. Shoot some emails to Cointaker.

Was on a thread about TZ flickering LED issues - https://pinside.com/pinball/forum/topic/led-strobing-in-slow-motion
Click to expand...
Actually an incandescent lamp lights every 1/120th of a second (well 1/100th of a second for UK 50hz) so it is lighting 120/100 times per second

An "El Cheapo" LED with no extra circuitry will only light every other 1/120th (1/100th for the UK) so it is lighting only 60/50 times per second.

By adding a bridge rectifier alone (even without a capacitor) you make the LED light on both the positive and negative cycles of the AC sinewave so 120/100 times per second, thus halving the flickering effect.

The lower the frequency, the higher the human flicker perception, so by default LED flicker is worse in the UK than America.

For most people, full wave rectified LED's don't have perceivable flicker. For those that are still sensitive to it, adding as much capacitance as possible to get the AC ripple to as near to zero will completely remove the problem
 
I don’t get the same level of nausea / headaches but the PBR machine you are speaking about does make me feel a bit funny for a little while after playing it. The strobing is very noticeable to me on that and a couple of other LED conversion machines around the patch, to some degree or another.
 
lukewells said:
Actually an incandescent lamp lights every 1/120th of a second (well 1/100th of a second for UK 50hz) so it is lighting 120/100 times per second

An "El Cheapo" LED with no extra circuitry will only light every other 1/120th (1/100th for the UK) so it is lighting only 60/50 times per second.

By adding a bridge rectifier alone (even without a capacitor) you make the LED light on both the positive and negative cycles of the AC sinewave so 120/100 times per second, thus halving the flickering effect.

The lower the frequency, the higher the human flicker perception, so by default LED flicker is worse in the UK than America.

For most people, full wave rectified LED's don't have perceivable flicker. For those that are still sensitive to it, adding as much capacitance as possible to get the AC ripple to as near to zero will completely remove the problem
Click to expand...

Great explanation.

I assume its less noticeable in incandescent as they will get brighter and dimmer from the AC cycle where as LEDs with light and then go off when reaching the voltage threshold needed to light them?

Would a better option be to use a larger rectifier on the whole GI circuit and include a larger capacitor to smooth the DC voltage instead, or even switch to a regulated PSU, assuming there is no fancy MPU control of the GI going on?
 
I've not noticed it on pins, but on old CRT monitors if the refresh rate was set anything lower than 60Hz I couldn't look at it for more than a few seconds before my head felt like it would explode.
 
Fantazia2 said:
Would a better option be to use a larger rectifier on the whole GI circuit and include a larger capacitor to smooth the DC voltage instead, or even switch to a regulated PSU, assuming there is no fancy MPU control of the GI going on?
Click to expand...
Once you swap to Leds from Incandescent, you can run the whole GI off the DC supply made for the controlled lamps, because you're not taking much current even with 100+ Leds compared to 100+ Incandescents.
It's as simple as just disconnecting the GI wires from the AC supply and putting them on the DC lamp supply.
 
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