Connecting a dwarf signal to a Fastrack accessory track

I guess what I asking is since post-war and some MPC do not have circuit boards this block diagram allows them to operate in a semi automatic way such as stopping when the semaphore signal is red and proceeding when it is green or does it not matter. I changed it for what I wanted it to do.

Denny,

I think the distinction is not between (A) locomotives which have circuit boards versus those which do not,  but rather (B) between locomotives which are operating under conventional transformer control versus those which are operating under some kind of electronic command control (e.g. TMCC, Legacy, DCS).

Because I have never tried it, I do not know what will happen if a locomotive operating under command control comes into a block whose center-rail power has been turned off by a relay, and then turned on again by that relay.  My guess is that the locomotive would reset to its initial power-on state; that seems to be what happens when I mistakenly run a Legacy or TMCC locomotive through a switchtrack onto a another track where I have forgotten to turn the center-rail power "On."

But if (1) a locomotive is operating under conventional transformer control, if (2) its direction-control has been set to "forward", and if (3) its direction-control (e.g. E-unit) has been turned off in the "forward" setting,   then it should stop when center-rail power has been cut off by the relay, and it should resume forward motion when the relay routes power again to the center rail.   (I have never tried this with locomotives that have circuit boards, but theoretically I am assuming that this is how they will behave.)

/Ralph

"Because I have never tried it, I do not know what will happen if a locomotive operating under command control comes into a block whose center-rail power has been turned off by a relay, and then turned on again by that relay.  My guess is that the locomotive would reset to its initial power-on state; that seems to be what happens when I mistakenly run a Legacy or TMCC locomotive through a switchtrack onto a another track where I have forgotten to turn the center-rail power "On.""

They, PS2 and TMCC locos have no memory when power is removed in command. When power is restored they will resume their neutral state,waiting for a command. I made a few circuits for DCS users where are train stops at a crossover and resumes in command after the opposing train crosses. If you leave about 8 volts on the track, it will stall and resume it's previous state when full voltage is restored. Some Gurus over at the DCS forum said this could damage PS2 electronics but I had no complaints from the people who used it. I only run conventional but my layouts are fully automated. I leave the E unit locked in forward or remove it and run it off a rectifier.

Dale H

I don't think there is much risk of damage driving a command locomotive onto an unpowered track, but as Dale says, you'll have to take some action to get it running again.  TMCC will stop and wait for a command when power is restored.  PS/2 will take off again if the power interruption is less than a few seconds, if it goes into shutdown you'll have to do the startup again and then get it moving.  Of course, if either of them are going in reverse, they'll revert to forward operation when started up again, unless it's the PS/2 momentary power interrupt.

I am using unfiltered dc as you described to power my 12 volt dc relays, what size capacitor can you recommend?

Thank you!

If you have a real DC supply, you don't need a cap.  If you use half-wave, or even full-wave rectified DC from AC, many DC relays will chatter with no filtering.  A 33uf cap turns out to be plenty for all the relays I've used.  With the smaller signal relays, I've taken to using a larger cap to give me a nice delay of several seconds for the release.  I also put a 10 ohm resistor in series before the cap to minimize the surge and the resultant small spark as the cap charges.

Thank you!  I will certainly give it a try with the 33 uf cap and the resistor as you suggested.  If I wanted to have a delay, what size cap would you recommend for say a two second delay?

The size of the cap is dependent on the current draw of the relay, the dropout voltage, etc.  I suggest starting with a 220uf and working from there.  I just select a part that gives me the correct delay.

well no electrical engineer here by any means but. I have signals red green and yellow. using fastrack  what I have done was simple for green and red yellow haven't figured out yet. tell me if I am doing it wrong.

red is 87b and yellow is 87 white is trigger and black is common - blue is power + my relay is a dc relay and would chatter and not switch the green off but would turn the red on. so what I did was grabed a dc adapter from wall wart and tied the ac common - from the zw80 to the common of the dc adapter then powered the relay + from the ac adapter then when the wheels rolled over the isulated rail it trips the relay green goes and red comes on. now my question would be 2 part how to get the yellow to work and does tieing the 2 commons together from the ac adapter and the zw80 cause a problem?

What length of delay are we talking about?

Chuck, it's very dependent on the characteristics of the relay in use.  I have some pretty large ones I was using, they sucked quite a bit of coil current.  I also have some small signal ones that only require 20ma coil current and will give me a few seconds on a 220uf capacitor.

Yes, I just wondered why one would want delay and how much. The relay holding probably until it's voltage is down to maybe one third of it's design voltage makes it experimental even though you can calculate the exponential decay of the capacitor voltage.

By the time you calculate it and figure out the relay specifications, I've build the whole signal and have moved on to another task.   This is one that is perfect for empirical testing rather than trying to compute it.