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Author Topic: Traffic Light - advice?  (Read 724 times)
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Topsham, Vermont USA
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Yes relays are the easy approach. See a 4-relay board like these:  http://yourduino.com/sunshop2/index.php?l=product_detail&p=201 

And Ultrasonic distance measuring is pretty easy. See: http://arduino-info.wikispaces.com/UltraSonicDistance


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HOW-TO: http://ArduinoInfo.Info

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Don't worry about retrofitting the voltage of the light, just use relays to switch the 120VAC to each light as necessary.

The problem with that approach is that you have to consider the safety of the relay, and the high voltage wiring to it, and anything else that is mounted on the same PCB as the relay. Any project that involves high voltages and electronics in the same enclosure is potentially dangerous. Unless you're aware of all the issues and know how to address them, I wouldn't recommend that for a DIY solution. The safe approaches are to either use something like a power tail switch, where the high voltages are safely isolated from the user-supplied electronics, or convert the voltages down to safe levels. It's easy enough to get 12V lamps in any power rating you want.
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Austin, TEXAS
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I'm all for safety, so develop at your own pace and comfort level, by all means.

I haven't had a problem with my traffic light controller.  I use a transformer to step down the +120VAC to +24VDC (a safe level) right at the entrance into the enclosure.  I then run the controller off of that, whose outputs control the relays, whose high voltage supplies come from the +120VAC input. Each relay turns an individual light on/off.  Two separate fuses are employed for safety.  The enclosure is a heavy-grade industrial unit that I got off of ebay.  Two fans keep things within the temperature limits specified in the controller documentation during the hot summer months.

Had the thing in my attic for over a year now, running continuously.  No worries.  I check on it periodically and realize that at some point I'll need to power down the unit to change out the fans due to mechanical failure from constant operation, but they're doing ok as of now.

But I digress.
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Topsham, Vermont USA
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Re Safety:

This relay board
Quote
has optical isolation.

I would suggest physically locating the relay in the Traffic Light housing, providing a small 5V supply there to run the relay driver and relay coil section, and bringing Arduino +5 and the 4 (or more) Arduino output pin signals to the light.  No AC or DC connection between Arduino and the Traffic Light Power. 

See some examples here: http://arduino-info.wikispaces.com/ArduinoPower 


DISCLAIMER: Mentioned stuff from my own shop...
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Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

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