Architectural Designs

Circuit design for traffic light operation?

My church has a traffic light for the youth building. We want to wire it up to use it as a timer...when turned on, the green lights will energize for 8 minutes then the yellow lights will come on for 2 minutes then the red lights come on. I do not know what type of lights a standard traffic light uses (ac or dc, volts, watts, etc) and we are trying to keep the control box/circuit design cost to a minimum. Any suggestions?

Public Comments

1. This can be done very nicely with 3 (interval type) time delay relays (green, red, yellow). When you close a switch power goes through the yellow light normally closed contact and the red light normally closed contact to energize the green light coil (then to neutral). The green light coil will be energized for (adjusted to) 8 min. During this time power will go through the normally open 8 min green light relay contact energizing the green light then to neutral. The yellow relay coil will be wired through the green normally closed contact and the red normally closed contact. When the green coil times out the green normally closed contacts close, energizing the yellow relay. The yellow relay will stay energized for 2 min. The yellow light will be wired through the normally open yellow relay contact which will be illuminated during this time. The red relay coil will be wired through the green normally closed contacts and the yellow normally closed contacts. When the yellow coil times out the yellow normally closed contacts now close, energizing the red relay. The red relay will stay energized for however long you want. The red light will be wired through the normally open red relay which will be illuminated during this time. Then the green starts and so on…. All circuits start from a power source through contacts, through coils (or lights) and to neutral. As to lights, buy lights appropriate to the environment. If outside don’t get a table lamp, get water proof lights. As to power If you can get away with LED,s great, less power, or 110VAC lights will work fine. Make sure you get relays appropriate to the power you are using. I too enjoyed rezef's reply. Buying an inexpensive programmable controller is an option, though the requirement of minimizing cost very quickly excludes it as an option especially if you must invest time learning how it works. The program logic will be exactly the same as I have outlined above. Inittiating communication between your computer and the controller is problematic. Additionally you need a little ladder logics knowledge for programming. Hey relays are basic, easy cheap and relyable. And even in the 21 century we actually still use them.
2. I enjoyed reading BRUZER's responce, I remember doing such stuff in my college days. But, it's a hassle, and it's so 1950s! Why don't you try a small PLC (programmable logic controller)? These are small inexpensive devices, which you can program very easily (Not really programming, they have nice graphical interfaces, you'll have no problem learning them) and are relatively cheap, less than $200. If you want to buy 3 delay timers you won't get that much of price difference either. A quick google search showed me this model: http://www.electrodepot.com/al10mra.htm Which sells for $149, and has a display on the unit so you don't even need to connect it to PC to program it, although you could in which case you will need the software for $39 and need a cable for $59. Another one I found is an Eaton model for $93: http://www.factorymation.net/s.nl/it.A/id.4474/.f but the software is more expensive ($99). Cable is $13. this one needs software and PC to program. Another one here: http://www.plccenter.com/ProductDetail.aspx?PartNum=HMICABC119&Manufacturer=FANUC&Condition=FNFP&source=Froogle