Working N scale traffic lights

[peteski]

Can you draw a diagram for that?  I can only get it down to 5 wires (4+1 common).

Jason

I just have all yellows together. There are some traffic signals which got from red to yellow to green.  But for separate yellows you would need 5 wired.

[wcfn100]

I just have all yellows together. There are some traffic signals which got from red to yellow to green.

Can't say I've ever seen that.  I think you can do that with three wires.

Jason

[C855B]

Yeah, I saw the red-yellow-green pattern in a few places in the South in the mid-1960s. The opposite reds and greens were connected together, and all yellows would illuminate (with the others still on). When the yellow went off the reds and greens would switch.

[peteski]

IIRC, red-yellow-green is also common in some parts of Europe.  The yellow tells waiting drivers to put the car in gear.

I don't see 3-wires thing. There are 3 distinct sequences, and one wire needs to be common to all 3. That is 4 total.

[Erik aka Ngineer]

Loetboy made these traffic lights work according to the German sequence, with yellow before green. Yellow and red are on on one direction, and yellow is on (after green) at the same time on the other direction. In this sequence you can have yellow on all sides at once, while still being safe.
He uploaded a youtube video. Please note that this is a testmodel, he has one set of traffic lights, with a 3-light pedestrian crossing (should have only 2, but he only had 3-light signal heads).

[parkrrrr]

I just have all yellows together. There are some traffic signals which got from red to yellow to green.  But for separate yellows you would need 5 wired.

If you think about it, there are basically four states on your average traffic light (not counting newer lights that go all-red for a couple seconds to compensate for scofflaws.) There's RG, RY, GR, and YR.

If there were no yellow lights, it'd be easy to use just two wires: wire the red light of one side and the green of the other side in one direction, and the red of the other side and the green of the first side in the other direction, and then the direction of the current determines the state of the light. Drive one line high and the other low for one state, and vice-versa for the other state.

Yellow adds an extra wrinkle that I think you can resolve with a three-state driver. Wire the yellow LED for each side "next to" the green of that side, in the sense that it's wired to the red of the other side in the same way as the green, but feed the free end of it with a separate wire. Now you have your original two wires, plus one wire for each of the yellow sides. Drive it the same as before, but when you want yellow on one side, float the green wire for that side while driving the yellow low. For green, float yellow and drive green low.

So, there you go: four wires, but you can't do an all-red indication.

(Disclaimer: I haven't tried this, and my knowledge of electronics fits on a napkin, in large print. But it seems logical.)

Edit: Thinking more about this, I'm not sure that you couldn't tie the two yellow lines together and get away with THREE wires.

[PennsyPride]

Interestingly I had this traffic light controller as part of an email from Jameco this morning.
http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&productId=2261191&catalogId=10001&langId=-1&CID=FREQ&trk_msg=BF4BRKL599RKL0NGPH6T42784G&trk_contact=0DH8JB4OLLTAV71G44RAFJL5VC&utm_source=Listrak&utm_medium=Email&utm_term=LED+Stop+Light+Kit&utm_campaign=FREQPROD&utm_content=FREQPROD