# Help me wire a traffic light. **URL:** \ **Category:** Factual Questions\ **Created:** [September 8, 2003, 10:05am UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247 "2003-09-08T10:05:08Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [September 8, 2003, 10:05am UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/1 "2003-09-08T10:05:08Z")
No worries. Do you want me to hold the wire while you solder it? ---
**Author:** ![Bruce\_Daddy](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Bruce\_Daddy](https://boards.straightdope.com/u/Bruce_Daddy)\ **Post date:** [September 8, 2003, 12:16pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/2 "2003-09-08T12:16:48Z")
Crap, how’d that happen? * * * Anyway, I’ve got a real traffic light that I want to wire to be able to switch the lights on and off. There are 4 wires, one common and one for each light. My first attempt with a a-b-c-d speaker selector was successful for about 10 seconds until the switch blew up and I tripped a fuse. So, for the questions: - Where can I get an a-b-c switch that can handle the current? - Is 110v the correct voltage? - Is 22 ga wire big enough? Thanks in advance. Damn you hamsters, don’t eat this one! ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [September 8, 2003, 12:22pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/3 "2003-09-08T12:22:00Z")
We need to know if the lamps are rated for 110 volts or not. Take out the bulbs and check. You can get a three position industrial selector switches from a variety of vendors and manufacturers. Try Radio Shack for starters or Allen Bradley. Are you going to control this by hand or is it going to be automatic? - Like real traffic lights. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [September 8, 2003, 12:25pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/4 "2003-09-08T12:25:24Z")
110 is probably the correct voltage. But 22 Ga wire is not good enough. I’m assuming it’s an older light with actual bulbs, rather than a new unit that might use LEDS. You need wire the correct size to carry the current required by the blubs. 14 Ga is probably right. Some traffic lights use 135 volt bulbs supplied with 110V. This makes them last longer. A speaker switch won’t handle the current drawn by the blubs. Each bulb probably pulls an amp or so. ---
**Author:** ![Booker57](https://avatars.discourse-cdn.com/v4/letter/b/b9e5f3/32.png) [@Booker57](https://boards.straightdope.com/u/Booker57)\ **Post date:** [September 8, 2003, 12:25pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/5 "2003-09-08T12:25:30Z")
Relays. A switch should not handle the full current load. If you wire three relays, one for each load, you can use the same switch as before. A new one. ---
**Author:** ![Bruce\_Daddy](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Bruce\_Daddy](https://boards.straightdope.com/u/Bruce_Daddy)\ **Post date:** [September 8, 2003, 1:07pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/6 "2003-09-08T13:07:01Z")
I forgot to add that just for snicks I twisted the 3 lamp wires together and used an old power cord and made all the light come on and it looks about right. Yes, there are bulbs, not LEDs. Where can I get a relay? I’ve checked Home Depot and Radio Shack’s website and only RS had some but they are all small. Can I use 14 ga wire and three wall switches instead? ---
**Author:** ![sparky56](https://avatars.discourse-cdn.com/v4/letter/s/da6949/32.png) [@sparky56](https://boards.straightdope.com/u/sparky56)\ **Post date:** [September 8, 2003, 2:13pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/7 "2003-09-08T14:13:57Z")
The wire used to feed your traffic light should be sized according to the ocpd (fuse,cb) generally,if it’s a 20a ckt,#12 should be used. #14 is good for a 15a ckt. Keep in mind that if the light is metal it must have an equipment ground run to it to be safe. A customer of mine ordered a controller from a company that I believe was called traffic [light.com](http://light.com) or traffic [signal.com](http://signal.com),I’m not sure. Be safe with the installation in any event. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [September 8, 2003, 3:23pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/8 "2003-09-08T15:23:38Z")
ocpd (fuse,cb) = Overcurrent Protection Device (fuse or circuit breaker) In relation to the circuit that feeds the whole traffic light assembly. In other words, If you use a fifteen amp circuit (according to the breaker in the panel) to control the lights, then you should use 14 gauge wire. Or 12 guage for a 20 amp circuit. **BD** - yes, you could use wall switches instead. How are you thinking of installing the lights? As a stand alone unit or mounted on the wall somewhere? And how do you intend to route the wiring for the whole thing? Just Curious. ---
**Author:** ![Bruce\_Daddy](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Bruce\_Daddy](https://boards.straightdope.com/u/Bruce_Daddy)\ **Post date:** [September 8, 2003, 3:39pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/9 "2003-09-08T15:39:40Z")
Here’s what I’m thinking: Wall socket slot 1 ---------------------------\> Common wire Wall socket slot 2 | | v Switch 1-------------------------------\>Red | | v Switch 2-------------------------------\>Yellow | | v Switch 3-------------------------------\>Green I was going to get a 3 switch place from the local Lowes or Home Depot and screw it onto a piece of wood or something, nothing fancy. The light itself could only be hung my something, and I haven’t figured that out yet. For now it’s just going to sit on the floor! That bastard weighs about 50 lbs. I’m not understanding why I need a fuse. Those outdoor spotlights are about the same brightness and they don’t need a fuse. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [September 8, 2003, 4:20pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/10 "2003-09-08T16:20:35Z")
There are many ways of wiring it. Probably the cheapest approach would be to use three standard wall switches installed in an enclosure of some type. The neat thing about doing it this way is that you’d be able to turn on the lamps independently (i.e. you’d be able to illuminate more than one lamp at a time). Keep in mind, however, that the traffic light’s common conductor must be capable of handling the current of all three bulbs if you decide to take this approach. If the common conductor is _not_ rated to handle the current, you could either install a larger conductor or wire each bulb independently. (And come to think of it, the traffic light’s enclosure would have to handle the heat. Hmmm. On second thought…) ---
**Author:** ![Bruce\_Daddy](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Bruce\_Daddy](https://boards.straightdope.com/u/Bruce_Daddy)\ **Post date:** [September 8, 2003, 4:26pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/11 "2003-09-08T16:26:05Z")
> [@](#): > > \*Originally posted by Crafter\_Man \* > \*\*There are many ways of wiring it. Probably the cheapest approach would be to use three standard wall switches installed in an enclosure of some type. The neat thing about doing it this way is that you’d be able to turn on the lamps independently (i.e. you’d be able to illuminate more than one lamp at a time). Keep in mind, however, that the traffic light’s common conductor must be capable of handling the current of all three bulbs if you decide to take this approach. If the common conductor is _not_ rated to handle the current, you could either install a larger conductor or wire each bulb independently. (And come to think of it, the traffic light’s enclosure would have to handle the heat. Hmmm. On second thought…) \*\* I don’t know if this counts for much but the guy I bought it from had one hanging in his store. His had all the lights on. When he explained to me how to wire it, he told me to twist the 3 together into one to make them all light up. It was obvious to me why there were three wires, but I didn’t say anything. The point is, he had his plugged into the wall with all three going, so it’s not that big of a deal, I don’t guess. Then again, getting electrical advice from an antiques store dealer :rolleyes: ---
**Author:** ![Bruce\_Daddy](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Bruce\_Daddy](https://boards.straightdope.com/u/Bruce_Daddy)\ **Post date:** [September 9, 2003, 1:13pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/12 "2003-09-09T13:13:56Z")
If anybody cares, I wired it exactly like my diagram above and it works fine. ---
**Author:** ![spingears](https://avatars.discourse-cdn.com/v4/letter/s/ebca7d/32.png) [@spingears](https://boards.straightdope.com/u/spingears)\ **Post date:** [September 9, 2003, 7:49pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/13 "2003-09-09T19:49:03Z")
The ‘wattage’ rating of the bulbs determine the current draw. Total watts determine total amps to lamp assembly which in turn determines minimum size wire needed, based on the single return neutral (white) wire. #16 insulated wire should suffice and be on the safe side. Contacts on R.S. selector switch may be too small. Check ratings(s). OR it could have been miswired. ---
**Author:** ![John\_Zahn](https://avatars.discourse-cdn.com/v4/letter/j/e0b2c6/32.png) [@John\_Zahn](https://boards.straightdope.com/u/John_Zahn)\ **Post date:** [September 9, 2003, 9:44pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/14 "2003-09-09T21:44:33Z")
> [@](#): > > \*Originally posted by Bruce\_Daddy \* > \*\*If anybody cares, I wired it exactly like my diagram above and it works fine. \*\* Does it go through the sequence?–Green, yellow, and red? Recently I was renting out a couple of buildings to the traffic light people that were going to the newer lights. They said we could have all of the old ones we wanted, so we took a few. My brother found information from the internet, and got a company that sold simple wire kits from something like $35.00 that let’s it go through the sequence like a regular traffic light would. JZ ---
**Author:** ![Bruce\_Daddy](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@Bruce\_Daddy](https://boards.straightdope.com/u/Bruce_Daddy)\ **Post date:** [September 9, 2003, 11:29pm UTC](https://boards.straightdope.com/t/help-me-wire-a-traffic-light/200247/15 "2003-09-09T23:29:44Z")
> [@](#): > > \*Originally posted by John Zahn \* > \*\*Does it go through the sequence?–Green, yellow, and red? Recently I was renting out a couple of buildings to the traffic light people that were going to the newer lights. They said we could have all of the old ones we wanted, so we took a few. My brother found information from the internet, and got a company that sold simple wire kits from something like $35.00 that let’s it go through the sequence like a regular traffic light would. > > JZ \*\* No, I manually have to flip the switches to make the lights turn on. I used regular wall switches (like, 50 cents each) and 12 guage wire. It was really easy.