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Author Topic: Traffic light sequencer  (Read 2882 times)

KungFu_ActionGrip

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Traffic light sequencer
« on: May 06, 2006, 08:46:46 PM »

Hey guys I recently purchased a surplus traffic light and I'm having a hell of a time finding a controller circuit on the web.  What I'm looking for is a circuit that will sequence through the colours in a realistic fashion (i.e. 30-40 seconds for green, 4 or 5 for amber, then another 30-40 for red).  It's going to be hooked up to 120v mains and has 60w bulbs in it.  Any help would be great :)
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viridius

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Re: Traffic light sequencer
« Reply #1 on: May 07, 2006, 12:01:03 AM »

What is the interface like?  Is it a separate wire for each bulb?
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KungFu_ActionGrip

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Re: Traffic light sequencer
« Reply #2 on: May 07, 2006, 07:15:19 AM »

There's 2 wires going to each bulb, but it's pretty easy to get in there and change the wiring if nessecary
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Mikecx

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Re: Traffic light sequencer
« Reply #3 on: May 07, 2006, 07:15:51 PM »

I wouldn't think this would be too hard with a microchip and a transformer. A few simple timer routines and you should be there. Not too sure how hard it would be to get 35-40sec out of a PIC but if you can't do it that way you could easily add a clock chip. I'd check the values you can get with a 4mhz oscillator but I don't have the time to do it now. If you did go that way you'd end up needing a transformer, a pic, a couple of transistors, maybe a clock, and that would be about it. If you didn't want to go the timer router you could also use a 555 timer and a high value resistor and capacitor. Not too hard to pull off if you know your electronics.

After a little quick review, a 4 nested timing loop should be able to pull off 35-40 seconds nicely. If I still had access to the EE Labs here i'd write you up some quick assembly but it's really quite easy code and I can write the basics of it here if you'd like.
« Last Edit: May 07, 2006, 07:22:18 PM by Mikecx »
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viridius

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Re: Traffic light sequencer
« Reply #4 on: May 07, 2006, 07:41:29 PM »

A microprocessor would be overkill for what could easily be accomplished by cascading three 555 timers, especially if you don't have the burn-in equipment at hand.  I don't know what you'd use a transformer for (besides powering the timing circuit), but relays or triacs could be used to control the individual bulbs.
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Mikecx

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Re: Traffic light sequencer
« Reply #5 on: May 07, 2006, 08:01:12 PM »

Microprocessors are cheap and easily available. I'd do it that way for the control and ease of changing but that's just me. Indeed it could be done with 555's for a few $$ less though you wouldn't have nearly as much control or customization. Either way both options are incredibly easy though you may want to go viridius's way, he knows more than me.

And yeah, the transformer would be used to power the pic unless there is an easier way to get from 120VAC to 5VDC.
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viridius

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Re: Traffic light sequencer
« Reply #6 on: May 07, 2006, 10:27:48 PM »

i7dude mentioned another approach that might be worthwhile: use a single RC circuit referenced by a few comparators.  Probably the simplest of the designs on the table now.  Not very temperature stable, but that doesn't matter too much for this application.  I'm swamped with work now, but I can get some schematics up by Tuesday.
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neostar63

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Re: Traffic light sequencer
« Reply #7 on: May 07, 2006, 11:32:52 PM »

I am not too familiar with the 555 timer, but I agree that any microcontroller will be overkill for what you are trying to do.
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Mikecx

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Re: Traffic light sequencer
« Reply #8 on: May 08, 2006, 10:29:22 AM »

I am not too familiar with the 555 timer, but I agree that any microcontroller will be overkill for what you are trying to do.

That really makes no sense. A 555 timer is quite simple and yet you know microcontrollers? If you want any kind of customization (isn't that what GT is all about?) you'd be not only ok with a microcontroller, but better off. I'm also not seeing where a $1.00 IC is overkill if you have access to a pic programmer (I have one, it was $10. Used it enough to make it worth it since). I realize the PIC can do a lot more than just sequence lights but that doesn't make it overkill.

I'm not saying PIC is the best idea but it works, it's highly customizable, and it's not all that expensive.
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KungFu_ActionGrip

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Re: Traffic light sequencer
« Reply #9 on: May 19, 2006, 05:25:58 PM »

Hey guys, sorry for not replying earlier I was off at the cottage with no 'net access.  Most of what you guys are saying is pretty greek to me, I have worked with 555 timers in the past but only working off a schematic that someone else did up for me.  If it's possible to go the 555 route I'd rather do that as I've got some and I don't know what else I'd use a programmer for so I don't want to buy one if I don't have to.
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