Blindman Traffic Lights (two pins for three lights)

sedeap

Senior Member
Blindman Traffic Lights (two pins for three lights)

This projects was made to one private-neighborhood.
To meet the regulations, they must provide some safe crossing pathway for childs, adults and blindmans. So I make this project using only two pins for three lights + activation button + night/day detection + sound tic (distinctive for blindmans)
That make some low rate tic noise to allow find the crossing pathway, and a high rate tic noise when crossing is allowed, during night the low rate, becomes lowest to avoid disturbing the sleeping time.
The button also is used in the night, to make shortest the waiting time to light changing.

Diagram HERE in PNG
Diagram HERE in JPG
Code HERE in txt
Code HERE in .zip

(i'm moving out the server, so if the link not work, try later)
Sorry for the incoveniences...
 
Last edited:

hippy

Technical Support
Staff member
This must be the most safety critical system we've seen a PICAXE used in - A blind person hears the high-rate ticking and has to take it on faith that traffic has been told to stop and will.

Along with the diagrams and code, do you have details of how you have ensured that what is meant to happen will always happen, that what should not happen will not ? A safety critical analysis, a fault-mode assessment, mathematical or other proof of the correct operation of your code ?

Did you have to take out public liability insurance to cover yourself in the event that something does go wrong with the software and someone gets killed or injured ?

In your circuit diagram, Input Leg 4 doesn't have a pull-down resistor, which would be recommended.

I could not see your code ( moving servers I presume ), but what have you done to overcome or minimise public annoyance should someone jam down the push button ? Does the system stick on "traffic stopped", repeatedly cycle between "stop" and "go", or handle this in a more advanced way ? Continually getting a "cross now" sound activation from a crossing broken that way is usually very annoying for local residents.

My experience of traffic light design is limited but a key component was a robust button which could withstand serious abuse. The force applied to a traffic light button is phenomenal. Most people would probably be quite surprised at the mechanical design ( using springs and concentric rings ) required to reduce the push to something which doesn't damage the microswitch finally used on the PCB. It has to 'last forever', be reliable in all elements, and immune from determined vandalism.

It's always interesting to see designs taken from theory to the real-world. There is invariably a lot more too it than simple software and circuit design.
 

sedeap

Senior Member
Master Hippy:

Tested?: Oh yeah. 20 months until now and still working.
Insurance?: Oh yeah. Double, one from the Private-neighborhood administration, and another from Industrial designs (compulsory) cover my designs.
Rascals & vandals?: not much, remember... Small, close, private-neighborhood with camera CCTV & private security personal, they check day by day the traffic lights, but just in case, I always use industrial switchs ( Thick aluminum body, sealed box ) but the really menace here are the ants... make havoc, eat (or destroy)the silicone seal of the electronic things and get inside & build nests.
Button missing or blocked?: only make the waiting time shorter, no big deal (not much traffic anyway... hahaha)
PullDown resistor?, you're right, in the diagram is missing. ( I was running to check the spare board parts... and is there...) Thanks!
(I will fix that diagram later ) The used one have Optocouplers MOC3020 & triacs bt137 instead of led lights.(220v bulbs)
I post pictures later (in low res also, hahaha):p
 

hippy

Technical Support
Staff member
Looks like you have all the bases covered there. Ants ... I'd never had thought of that. There's a moral there; always expect the unexpected.
 

sedeap

Senior Member
Ants...

Dear Hippy:
Our menace conquer the world... (Sorry):eek:
Here the little ant is a real havoc machine !


See the little ant in the newspaper Here (in Spanish)
Or the article in the Educational environment Here (Spanish-English)
or the whole website about them. here

:confused:
 

papaof2

Senior Member
Ants in the US also like electronics - they destroyed a remote temperature/humidity sensor that was hanging form a tree limb by a foot of rope. Not sure what the attractant is, but it appears potent, since the ants went 8 feet up the tree, then 3 feet out the branch, then down the rope.

John
 
Top