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Topic: Project HELP. Wireless Fire Alarm system. IMPORTANT (Read 1 time) previous topic - next topic


You should also consider colour blindness - some people cannot distinguish red/green. And visibility in smoke.


That's right, in fact red/green colour blindness is very common in males. I hate those bloody battery chargers that have bi-colour LEDs, I can never tell when the batteries are charged :)

What I don't understand is that probably 90% of engineers are male, so how come this is so common? Surely someone puts there hand up and points the problem out.

Rob Gray aka the GRAYnomad www.robgray.com


IMO, I would consider hard-wiring.  Maybe even PoE so you have a single data and power line.  Or CAT5 UTP delivering serial + power.

Give each node a zone ID/address and send the same data to each.  Then, your data consists of an array of zones/addresses and a flag (safe/unsafe).  This simplifies your wiring to where it can be a bus, or star, or daisy chain.  As long as each node gets the data and is assigned the proper address (written to EEPROM?), you're good.

You might try keeping with the green/red idea, but also using a secondary element, like blinking or chasing, which might help with both intuitive action and color-blindness.

It might seem kinda "sci-fi" and superficial at first, but doing a chase pattern down corridors could help steer folks toward a safe path.  Delay each successive node by (e.g.) 100 ms, so the lights blink 'toward' the exit .. kinda like you might see on a runway at an airport.  It would be easy to do with an addressing scheme, where maybe the low three or four bits of the address get used as a delay factor.  Then you can turn on a safe zone, and all nodes in that zone delay by (100 * (addr & 0x07)) for instance.  Hope that makes sense.

Of course, each zone could be controlled by a single Arduino, where you use 8 outputs to drive LEDS (or transistors that drive LEDs) instead of dedicating a device for each set of lights.  (Maybe that's what you were originally thinking of..)  Then you can still chase by delaying the pins in succession -- maybe by using PORT commands and bit shifting.

Unsafe zones (or routes that lead away from an exit) can be marked by flashing all lights in the zone red, simultaneously.

If you were confronted at a T, and one way had flashing red lights, the other green lights that chased down the hall, which would you instinctively follow?  Even if you were colorblind, I think the effect would be sufficient.

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