Electronic gurus- can this be done?

Yes it can be done with a chips that senses when voltage exceeds 10V.  But why would you turn off ditch lights,  I thought they were protypically on from start to finish.  Some ditch lights alternate flash when horn sounds or triggered by engineer.

I build a circuit that senses motor voltage and closes a DPDT relay for a couple of locomotives.  I use it to control the cab lights and smoke unit in one of them, and the other one used it to cab lights and to implement Rule-17 lighting in another.

It's not quite as simple as it seems at first, the circuit has to be bi-polar, and it must be totally isolated from track voltage.  I ended up using a Schottky bridge rectifier and opto-isolator to sense the motor voltage, the other end of the circuit runs off track power to manage the relay.

As Sam says, not sure why you'd want to turn the ditch lights off, they normally run with them on.

For conventional, you could get fancy and add a circuit to the ditch lights to alternately flash them when the horn is sounded.

Hi John, I follow what you are saying but Bob obviously wonts this to be on board the engine so as to control the ditch lights.

I have an idea that might work but I'm not sure if the real estate could be found inside most engines to do it.

How about a five volt zener diode to fire on the lights that are driven through a Bi polar flip-flop like you say and a 10 volt zener diode to reset the relay pair back to off. What do you think, could this work and can the associated board be made to fit inside most engines?

Well, the board that I was referring to was indeed on-board, the module was .9" x 1.2" square and about 3/8" in height.  It fit into the little MTH 0-4-0 Docksider after I added TMCC, so I suspect it would fit into most locomotives.   Here's the finished module, I'm working on a PCB design so I can make them easier.

A simplistic solution could be done with two relays in series and different coil voltages. Some experimenting would have be done though as relays with a given coil rating usually close at lower voltage then what its rated for. I would start with a 10 volt SPST and a 15 volt SPDT. The lights would be fed from the normally open contacts of the lower voltage relay and the normally closed contacts of the higher rated relay. You could probably dial in the voltage closer to the desired 5 and 10 volts with resistors in series with the coils.

Electronically there are many ways to do it but involve many more components then the above solution.

The relays used on Williams E units might work here.

Pete

Hi John, that looks great I was off on a little diffrent track with zeners, op amps and three volt relays. I figured that I could get the size down to about 2cm X 3cm board.

Pete your idea is the most simple way to go, to be honest it's where I started on this problem. The two issues I thought about is the size and reliability of 6 and 12 v relays. They will work ok but as you stated above when they fire is depended upon conditions.

Also the ones I worked with take up more space then I think we have to work with.

John, on the other hand has a very nice wheel and I see no reason to invent another one.

I do have a question though John; how to you differentiate between the 5 v turn on and the 10 Volt deactivation of the ditch lights?

You can actually get very small relays, the ones that I use are .3" x .3" x .4" in size.  They come in a variety of coil voltages.  However, I think relays alone would be somewhat problematic.

I guess I don't see why that particular functionality is desired, I want the lights on when the locomotive is moving, and the cab lights off.  Now, if you were doing ground lights, those come on at low speed and turn off as you get going.

Ok John, I just went back and read your first post again, never mind!  

Mario, The relays i was thinking of are the size of a 14 pin DIP. They are available with mechanical contacts like a reed relay or have electronic switches inside.

Pete

Hi gunrunnerjohn,

Could you point me to somewhere that has these relays, and what to look for when I get there. Not for this thread, but I think these could maybe come in handy sometime for something.

Thanks!

Thanks Pete, I'm getting a little old and out of the loop. I need to spend more time on line finding out about new products.

I was looking at solid state relays, but again I never worked with them.

Try www.Mouser.com. But, then again that might be old hat like all my other ideas.

If you put this in series the motor,

www.jcstudiosinc.com/BlogShowT...=488&categoryId=

tapping the 2 ends of the diode string should power the ditch lights. Run one lead of the lights through the NC contacts of a small relay. Put the 12VDC relay coil in series with a 10 volt zener diode,run off the motor or track circuit. When the relay activates it should shut off the ditch lights. 12VDC coils can usually take up to 18 volts.

Dale H

Actually Mario I was using these relays back in the '70s. Time flies.

Pete

Sure, I get them at Digikey, they are in the the AXICOM line.  They're 14.6mm x 7.2mm and 9.5mm high.

Here's what's in stock at Digikey: http://www.digikey.com/scripts...V-5=4937&stock=1

Thanks,

Will go check them out. Working on an order there now. And BTW, Digikey is a great place, extremely fast & cheap shipping, good pricing, nice packaging & gets delivered 2nd day after ordering. Tried them from one of your other posts!  Make that a double thanks

Digikey and Mouser get most of my parts orders, between the two I can get most electronic parts.  The major exception is LED's, I get them from all over, since the prices and availability vary widely.

I went to Digikey John and I liked it. I heard of it before but I always go to Mouser first and usually make do with what I find there. As for the Digikey web site it is very similar to that of Mouser. The products are diffrent but the search works much the same, so I was right at home there.

I also like the fact that on both sites they provide a product DATA sheet with all dimensions and electrical characteristics.

Thank's buddy, good tip.

Great ideas folks....thank you.

John, while I don't work for the railroad, it was my impression that the ditch lights were just for start up/rolling - a "hey, look out I'm moving now" thing ...then they went off after the beginning of cruising speed...maybe I'm wrong there. 

Here's a good definition of Ditch Lights and Crossing Lights.  It appears that the two functions have been merged as you read down the page, the common term is now Ditch Lights for that function.  On interesting take-away from that page is that the Federal regulations no longer require flashing them, leaving that up to the individual RR.

Ditch-Crossing  Lights