Mount an infra-red heat sensor (as used in household alarms) to the front of jet skis to alert the rider to the presence of a swimmer in the waters ahead.
An audible alarm would sound, and failure to take evasive action would cause a timing device to cut the motor.-- Helium, Jan 12 2002 People Specific Infrared http://www.alarmsbc...Infrared Detectors:See Passive Infrared Detectors [Helium, Jan 15 2002] http://www. [Helium] I hope you are not offering that puny paragraph of sales talk as proof. "Special signal processing" is probably pretty limited on a $25 device. [bristolz, Jan 15 2002] People Specific Infrared http://www.alarmsbc...frared%20Detectors:See Passive Infrared Detectors [Helium, Oct 04 2004, last modified Oct 21 2004] FLIR (Forward Looking Infra Red).
On a warm, sunny day would the detector be able to distinguish a human's heat signature amidst all the noise of the sunlight reflected from the surface of the water?-- bristolz, Jan 12 2002 Welcome back Helium - would it be a timing device or another device that would keep Helium from causing further damage to swimmers scalps, folks?-- thumbwax, Jan 12 2002 I think time is a factor here, it should cause the jetski to flip in the water & rotate 180 degrees to send it back away from the swimmers-- po, Jan 12 2002 Combine FLIR and SONAR for greater accuracy.-- phoenix, Jan 12 2002 Flirting usually works best when Sonars are in sync BTW-- thumbwax, Jan 13 2002 [bristolz] Infra-red heat sensors are specifically designed to detect body heat, which is why house alarms also aren't activated by the heat of the sun.
[thumbwax] No scalps were harmed during the forming of this idea.-- Helium, Jan 13 2002 I just think it would be very hard to tune an IR device to distinguish a swimmer amongst all the thermal noise coming off of the water.
House alarm PIRs are designed to detect heat signatures of things that are in motion. You can fool them by moving very slowly. The sunbeams that cast in through the window don't move fast enough to trigger the PIR. However, I have had them go off when a column of heat came rushing through the floor vent on a cold morning.-- bristolz, Jan 14 2002 Bristolz: Remember that the jet-ski is moving, so to the POV of the sensor, everything would be...-- StarChaser, Jan 15 2002 [SC]: Yeah, but that's just a cheap-ass house version of the PIR I was talking about. I was pushing back on [Heliums] assertion that house-alarm PIRs are tuned to see human bodies, which I doubt. I think a PIR builds an image of an area and keeps sniffing the area for changes. If the thermal image changes relative to the last scan, or sniff, the PIR sends a "Whoa! Something has changed!" signal. The threshold of change can be tuned on these to ignore small animals. But they can be fooled by moving very slowly.
Be that as it may, my whole point, and it is a question or a ponderment, is: Do you think it is possible to tune an IR device to see through the thermal noise that comes off of the water on a hot day so that the FLIR sees the swimmer? I know a lot of thermal energy is reflected off of the water surface.-- bristolz, Jan 15 2002 [bristolz] Re:link
*crushed* As puny as it is, that's the best I've been able to come up with bar ringing a manufacturer. give me some more time.-- Helium, Jan 15 2002 Oh no, don't be crushed. My point is only that those house PIRs are so cheap and crappy that I cannot imagine they do much outside of the barest minimum.-- bristolz, Jan 15 2002 how about having it detect whene there's NOT motion ( when your heading straight for that pearson ).-- my-nep, Oct 31 2003 a fine idea. Surely Helium there's some military / commercial ship collision avoidance (sonar-based?) system that can be ripped off and cheapened for the purpose?
Safety third, -Josh-- white, Nov 02 2004 A sharp blade fixed horizontally just below the water line would cleanly remove the swimmers head and thus prevent any risk of injury or damage to jet ski and user.-- Belfry, Nov 03 2004 random, halfbakery