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Medical Forum / General / Vision / April 2007Persistance: What is decernable
Ok - Trying to keep from getting rear ended by 15 y/o tailgater while snowmobiling. I'm going to make2 brake/tail lights with 25 superbright LEDs with each LEDl being fully programable. The two right and left would display a mirror pattern of the other. Two things: For running mode I will be using rotating patterns wherethe rotating speed of the patterns is tied to speed of the snowmobile. 1. How fast of a rotation rate would become undistinguisable? I would think much more than 5 rotations per second would be the upper limit? These will be almost 2 1/2 inches in diamater. 2. Many experts say a rapid plusing is a good attention getter for braking: How many pulses per second would become ineffective? Is this a good place to ask these questions? : ) Thanks > 1. How fast of a rotation rate would become undistinguisable? I would > think much more than 5 rotations per second would be the upper limit? How many frames per second does it take to make a movie stop flickering? 15? It varies with illumination, target size, and eccentricity from the line of sight. > 2. Many experts say a rapid plusing is a good attention getter for > braking: How many pulses per second would become ineffective? The upper limit would be 15ish, 5 seems too slow. I like 10. > Is this a good place to ask these questions? : ) Yes. :) -MT > Ok - Trying to keep from getting rear ended by 15 y/o tailgater while > snowmobiling. Great project idea! > I'm going to make2 brake/tail lights with 25 superbright LEDs with each > LEDl being fully programable. The two right and left would display a [quoted text clipped - 4 lines] > would be the upper limit? > These will be almost 2 1/2 inches in diamater. As Mike Tyner wrote, it depends upon a number of variables. Are you going to have a single LED lighted at one time, advancing around, or multiple? To my mind, having roughly half the LEDs hot, turning on a new leader and off a trailer for each step, you could certainly go to 5 rps, possibly up to 10, at full speed. > 2. Many experts say a rapid plusing is a good attention getter for > braking: How many pulses per second would become ineffective? I would say 10 pps. You might take ambient light into consideration, slowing both the braking and running rates under low light levels. I'd guess you're planning on using a microcontroller of some sort (who bothers with 555's for this sort of thing any more?), so you'd have a lot of latitude for control and variability. > Is this a good place to ask these questions? : ) Thanks If you can get past the ad hominem replies to resident eccentrics, it's a great place for vision-related information... Dave I've been thinking about a strobe (Xenon, not LED!) adjunct for my Miata airhorns for some time. It's nice that they can hear you, but it's even better if they can see where you are, as well. Thank you both for the info! I have read about the 15 pps - but was So Long ago and I saw it only once or twice it would have Never come to my mond!! Thanks!! >>getting rear ended by 15 y/o tailgater while snowmobiling. > Great project idea! Me, and his Grandpa who owns the sled he rides, telling him to back off has yet to work. Maybe if we start calling him 'Butt Sniffeer" it might work as he is So Homophobic! ;) > > Are you going to have a single LED lighted at one time, advancing around, or multiple? > To my mind, having roughly half the LEDs hot, turning on a new leader and off a trailer for each step, you could certainly > go to 5 rps, possibly up to 10, at full speed. Several different pattererns that alterante between each slow down and brakeing that also alteternate every 5 seconds or so clock/and conter clockwise when spped is sort of consitant and no braking. But, I'm thinking the main Idea out of 12 LEDs in the outer circle to be two leading LEDs at full brightness, following by two at 1/2 and two at 1/4. > >You might take ambient light into consideration, slowing both the braking and running rates under low light levels. I never thought of that - wopuld add to the programing but doable - Make a difference you think? > > guess you're planning on using a microcontroller of some sort Yup looking at the moment with the Newest and Fastest PicAxe with 3 of the PAK-V co-processors. any better way of going? I am a newbie - But learing!! 555 what?! :) have done some programing, NO hardware proto typing but Very well read and good at finding out. Thanks!! > > >You might take ambient light into consideration, slowing both the braking and running rates under low light levels. > I never thought of that - wopuld add to the programing but doable - > Make a difference you think? My thought was that persistence of vision would more readily cause the spinning lights to merge at low light levels. You could use a simple photoresistor (CdS cell) into the PIC, and sense a few levels. No need for high resolution! > > > guess you're planning on using a microcontroller of some sort > Yup looking at the moment with the Newest and Fastest PicAxe with 3 of > the PAK-V co-processors. > any better way of going? Not familiar with the PAK-V, but it sounds intriguing. I'll check it out. PIC should do fine for you. > I am a newbie - But learing!! 555 what?! :) Tsk... What are they teaching you kids, anyway? Analog IC timer, first released by Signetics, if memory serves, back in the early 70's. Still finds tons of hobbyist uses. Dave >Ok - Trying to keep from getting rear ended by 15 y/o tailgater while >snowmobiling. [quoted text clipped - 3 lines] > > I've often thought that a better way to get someone's attention on your brake lights is to make them appear to get larger than normal, just as any object does as it gets closer to you. This would only require that there be several concentric circles of LEDs which would light up in sequence from inner to outer, each ring staying lit as subsequent rings are lit. Probably has been invented, but if not, you saw it here first... w.stacy, o.d. Yup - that was going to be the patteren used for rapid slow down without braking. My snowmobile slows down really fast when realeasing the throttle. But, hey - I'll cut you in one the Royalties! : ) > I've often thought that a better way to get someone's attention on your > brake lights is to make them appear to get larger than normal, just as [quoted text clipped - 4 lines] > > w.stacy, o.d. >2. Many experts say a rapid plusing is a good attention getter for >braking: How many pulses per second would become ineffective? More like distraction producer. Such brake lights on the road can be dangerous. The idea is to be noticed, not draw and hold attention. The change from off to on, or dim to bright, is quite sufficient for brake lights.  Signature- Mike Ignore the Python in me to send e-mail. |
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