a wrist band that has a led light that flashes from a push button

Run wires from your Wristband's LED, to a Cellphone?

Call it with another Cellphone, the display backlight comes on, powering the LED.

I'm not sure if you're serious, but I think if the kid could have a cell phone on them while swimming they woulden't need a wristband to page/locate them.

Triode said:

By transmitter do you mean that it transmits visible light, or are you talking about an IR led? Does it just blink while you hold the button or do you want it to stay on for a time period or untill the button is pressed again. If you want it to go a mile im guessing its an ultrabright led, and do you mean a mile of visibility at night? How light (weight) does it have to be and does it matter how fast it blinks? What is it meant to do when it recives light?

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Hi Triode,

do you know that a glowing cigarette end is clearly visible more than 8km (5miles) at night?

(in war time a sniper would shoot that cigarette butt right off your mouth - not from that distance, but sneeking closer).

A flashing LED has much more candle power than a cigarette end and is clearly visible at a distance of 20 miles - about the same light intensity when snipping a Zippo.

Please keep that in mind in case you want to survive at a front.

I know what I'm talking about because I had special training as sniper.

Boncuk

I know it could be seen that far at night, thats why I asked if he meant at night. I think during the day he would need an ultrabright led to have a chance of seeing it from that far, considering were talking about a water park, lots of kids, sunny day, sparkling water and white concrete dont make for an easy time spotting a light.

Radio links worn by child while swimming ? scary They'd have to all have uniquely addressable as well as completely waterproof, and have a sensible battery life.

How about instead marketing a secure wearable waterproof cellphone or radiopager pocket? Savvy parents and sponsors would more likely trust something simple than trust DIY technology no matter how clever it looked.

Or if it really does have to be a wristband electronic system that's kid-proof that parents would trust, how about a decent power "induction loop" installed around the area perimeter? If signal received by a wristband is lost, the band activates. Individual bands are each assigned a different frequency below the VLF band, a power amplifier about a kW drives all frequencies simultaneously or round-robin TDM. Locate one band by turning off the appropriate signal. Or have them all on the same VLF frequency, but addressed via PCM. To get sensible battery life the receiver would only be on a narrow time slot, have a timer to wake it for its listening slot and then go back to sleep.

Radio links worn by child while swimming ? scary

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I agree with you about it being somewhat impractical, but it isn't dangerous, were talking about one or two button cell batteries, and the whole thing encased in polymer or sillacone. Even if it got water in it, there's no way a button cell is going to shock anyone, lacking some combination of a Joul theif and a large capacitor.

By scarey, I mean it's scary depending on technology alone in order to find and locate a child. And UHF radio doesn't work that well with water around.

I think most would feel the happiest if the area was within cellphone coverage, then at least a wearable waterproof pager would be viable, or cheaper still a cellphone somehow.

How about a wireless doorbell. Press the button on the transmitter, and a sound (and or an LED) would be turned on. I believe they work from pretty far away, and there are no legality problems to worry about. If more range is needed, you could use an amp to strengthen the transmitter. You could easily turn them into what you need!

I agree that if this can be made practical at all, it would be using a premade device

Give the kids waterproof wristbands with RFID tags inserted.

Then make all the rides and gates have RFID readers, and central computer knows exactly what area any child is in at any time.

Make the kids enter name into a simple terminal when they enter the facility, name is linked to the wristband they were given, so a parent can ask for kids by name, or give the parent a matching wristband?

And finally make the wristbands a requirement to actually use the rides and get from area to area, maybe even implement prizes etc to encourage the kids to not take them off.

Then make all the rides and gates have RFID readers, and central computer knows exactly what area any child is in at any time.

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Brilliant! Wristbands are becoming common at concerts and other events, no one would even blink.

yeah, RFID would be the most effective way I can think of. I'm just not sure he has the authority in the park to install all that.

Do you run the park or work there?

Companies supply complete systems personell 'ID Badge' access control already.

e.g. RFID Applications and Solutions: ID Badges and Access Control (Badge readable up to 5 meters away)

or. **broken link removed** (2 -way data exchange, or 'where they've been')

Central computer logs all the movements.

UHF WRISTBAND (H86-SWB-L40) H-86-SWB-L40 RFID CZ products

UHF wristband

Thanks tren, thats an awesome link, so maybe my idea isnt all to crazy, I really dont know what I am looking at but I will definitely look into this.