programming track setup questions

[jward]

i am in the process of setting up a permanent programming track. this will be a dead end spur that will double as a fuel station. the setup i am considering is to use a caboose industries hand throw, with a set of contacts, to energize a dpdt relay to switch from programming to track power when the switch is lined for the spur.

the hand throw has only one set of contacts, which i will also need to use to power the frog.

will the current drain of running a locomotive cause the relay coil to drop out? only one locomotive at a time will be using the spur so current draw should be minimal. i would like to wire the relay so that the coil is energized only when the switch is lined for the spur. and when the switch is lined the other way, the relay will drop out and connect the track to the programming outputs.

should i use a resistor to limit the current to the relay coil?

has anybody tried anything similar, and if so how did it work for you?

[Jim Banner]

The answer depends somewhat on the DCC system you are using.  If yours has a reduced output for programming, then you might well have problems with the relay dropping out.

A better solution is to use the contacts on the hand throw to power just the relay.  This might require electrically isolating the hand throw (I don't know how it is wired internally.)  Once you have the relay working, you can use two poles to control siding power and a third pole to switch the frog.  For this, you would need a three pole double throw (3PDT) relay.  Personally, I would go a step further and use a 4PDT relay with the fourth pole turning on a bright red LED located right at the gaps for the siding.  This would help to remind me not to cross the gaps while I am programming and test running the locomotive on the siding.

Multi pole relays are often available on the surplus market for surprisingly low prices.  I recently bought a bunch of 4PDT relays for less than $2 each.  They happen to have 40 volt coils, but not to worry.  I found a 24 volt ac wall wart (used, $2) to which I added a bridge rectifier and a filter capacitor (1000 micofarads at 50 volts.)  The output of this dc supply was a few volts under 40 volts, but close enough to keep one or several of these relays happy.

Jim 

[OldTimer]

I have an easier way (although not as fun).  Power the frog with the SPST contacts built into your Caboose Industries ground throw.  Put a DPDT toggle switch in your fascia at the site of the spur.  Gap the spur past the frog.  Connect one side of the DPDT switch to the programming output of your command station and the other side to track power.  No relays or wall warts required, but you do have the extra toggle to throw.  But you all knew that.   

[jward]

O t
i had considered a dpdt switch, but i want to avoid any possibilityof accidentally running a locomotive onto the programming track while it is in program mode. thus the relays.

jim,
i have looked for 4pdt relays but there aren't available here except by mail order. and 1 of an item, no matter how cheap, gets expensive when you add shipping.
the canoose industries switchstands have a sliding contact on the throwbar which makes a mechanical connection. they are completely isolated from the track unless you wire them to the track.

i suppose there is always the possibility of wiring two relays in parallel to get my 4pdt.

i will experiment further and see what works best.

[RAM]

I just use a dpdt switch.   How often do you program a locomotive.  I would say not very often.  I don't think anything major would happen it the switch was wrong and tried to run a locomotive onto it.  I would think it would just stop. 

[jward]

i have heard that it could fry the programming circuitry. i know many people have used programming tracks completely isolated from th rest of the layout. that is what i have been doing.

as for how often you use the programming track, it depends on what you are doing. sometimes i get a bug to adjust sped curves, momentu and other effects. when that happens, i will use the track quite a bit.

[RAM]

I guess if you wanted to you could wire in a red and green light.  If it is red (program) you do not pass signal.  If it is green you are part of the layout.  This is when you are using the dpdt switch.

[Jim Banner]

If your decoders and command station support it, Operations Mode programming (a.k.a. programming on the main) is quick and easy and you don't even have to stop the train, let alone run it into a siding or special track.  This is particularly handy if you want to increase momentum when you pick up a train.  If you are double heading, it takes a little longer to do both locomotives, so you might want to stop for a minute while you do it.   Just after you couple them on to the train is the perfect time.  If anybody asks what the holdup is, just tell them you are making up the air.

Jim