Running PRR signals - how to wire

The thing with these signals is they use the center rail to control the red and green signals. the yellow is on a timer circuit after the red has been triggered and is switched back to green. The timer circuit turns on the yellow and after a certain time switches to green. it was designed for a IR sensor. I use a automotive 12vdc SPDT relay due to I'm a automotive technician and have a large collection of relays. I use a 4amp bridge rectifier to power the relay. with the relay off, the circuit is switched to turn on the green. When the train runs through the isolated track, this supplies voltage connection to the relay and switches the contacts to the red signal. after the train passes, the relay switches back to green circuit but the yellow lights come on with the timer circuit and then green. It's very simple. wire one from transformer hot to the AC terminal of the rectifier and the other coming from the isolated track to the other AC terminal of the rectifier. DC+ and DC- of the rectifier goes to the coil of the relay(doesn't matter where + or - is wired on the relay coil as it is not specific how it is wired. the coil will work either way).

 

The only thing with this circuit is you will get flickering from dirty wheels or traction tires on locos. Also run the signals on aux power hookup at 12 volts. If you wire it to track power, the voltage could be too low to operate the relay.

Relays can be purchased from auto parts store and bridge rectifier can be purchased from Radio Shack. If you need a diagram I can draw one up. Very simple.  

I use a 22uh choke (DCS compatibility), diode, capacitor, and a 12VDC relay.  That gives me chatter-free contacts to drive signals from the insulated rails.

 

GRJ, is the Hennings lighting board available a la carte?  I can't tell from the web-site.

 

That is, I agree that a handful of low-cost components can do the job but like the 12V LED strip wiring there are lots of guys that don't want to fuss with soldering, wiring, sourcing components, etc.

 

So.  If you replace the 12V DC LED strip with a 12V DC relay (plus a diode across the coil), couldn't that lighting board (IIRC 45mA output?) implement this? 

Stan, it is, but that part of the site is a little confusing.

 

LED Constant Current Lighting Regulator, 2Pcs

 

 Thanks JOHN FOR THE INFO ON THE LED REGULATORS. WILL SURELY TRY A FEW. TOM

If you have any questions, just let me know.

 

Well, I had to see if it would work...

 

So here we have the Hennings LED lighting board connected to an isolated-rail simulator (blue masking tape).  Track voltage from Z4000.  LED board set to maximum output current (about 45 mA) driving an eBay 12V relay module - the one's that are just over $1 (free-shipping from Asia).

 

Worked fine over a 10-20V AC range.  Here it is in action. The relay module has a red LED which turns on bright when the relay trips.  Note the LED brightness decays rather than suddenly turning on-off which is from the capacitor performing its anti-chatter.

 

Looks like a winner.

 

Here are 3 other off-the-shelf isolated-rail-trigger relay modules that have been discussed in the last month or so on OGR.  If anyone else has photos or diagrams to add of other off-the-shelf relay modules, it might be useful to consolidate tack that on here (for the record). 

 

Azatrax MRAPR and Lionel 153E shown below in photo from another thread:

 

https://www.azatrax.com/track-power-relay.html

 

The 153E seems to be discontinued or very hard to find.  The Azatrax does not appear to have a capacitor on it but I don't have one so don't know for sure.

 

 

Train Electrics MTR-12T

 

http://www.trainelectrics.com/relays.html

 

 

If with roll-your-own, here's a write-up by Dale H about what's going on under-the-hood at the component level which has photos of his implementation:

 

http://www.jcstudiosinc.com/Re...Rail-Block-Detection

 

And here's GRJ's schematic I copied from this thread where he posted it.  He might have a photo of it somewhere but I can't remember.

 

I don't know that I posted a photo of these.  I built them out of salvaged relays, and put them onto small wooden platforms.  They get screwed under the layout and powered from track power, hence the choke for DCS and the resistor to limit the inrush current.  They work very well on 18V, and I never have to go back and tinker with them, they're pretty bulletproof.  It was a pretty crude assembly, I super-glue the relay upside down by the case.  I also had a barrier strip for the connections so there'd be no soldering under the tables when we were installing them.

 

 

I use a bridge rectifier on a DC relay. Then add a 500uf or a 1000uf

on the DC side. The 1Kuf gives me about a 1 second delay after the

train passes. I like the effect. This configuration also prevents

relay chatter.

This is a kind of "roll your own thread" on isolated rail triggering.

My lowly diode and 220uf capacitor has never chattered, at least none of us have ever noticed any of them doing it.  I figure the signals will add any delay if they so choose.

 

I looked through eBay and couldn't find the relays shown above, anyone know if these are still around?

http://www.ebay.com/itm/12V-1-...;hash=item20e865f2c8

 

 

Thank you, Stan!  I couldn't find them after 30 minutes of searching - I just ordered two.

Well I just got these in the mail today and already burned up one - can someone please tell me how to hook these relays up?

 

Question - is the relay linked in Stan's post above a direct replacement for the one sold by Scott's Odds n Ends (Train Electrics)?

 

 

Thanks

What are you trying to do?  Drive signals?  Are you using isolated-rail block detection with the accessory voltage from a transformer?

 

Out of curiosity what burned up?

 

No.  The Train Electrics relay accepts AC or DC input; the eBay relay is a DC device.  The Train Electric relay has 15 Amp contacts; the eBay is 10 Amps (albeit I don't think you need 15 Amps for anything to do with signaling).  But then the Train Electrics relay is $17.50 while the eBay relays are less than $2 w/ free shipping.  Part of the story in this thread is how you might save some $ if you are willing to fiddle with some components to allow the DC-only eBay relay to operate on AC.  As shown earlier this AC-to-DC conversion can be done by $1 or so of assorted components like diodes, capacitors, resistors, etc. but soldering and fussing with small parts is not everyone's cup of tea.  I was showing how GRJ's LED lighting board could also perform this AC-to-DC conversion.  Frankly I wouldn't expect anyone to do this and was more a case of idle curiosity that I tried it.

 

Great info...thanks for providing everyone.

-Greg