I'm so elated!!! Dallee Train Detection Circuit

[cwclark]

Hi guys,
Well i finally got them in..it took two weeks to wire them all, but my Dallee train detection circuits are in and they are working great!...the train comes into a block and the light goes from green to red, the train leaves the block and the light goes to yellow and then the train enters the final block and the light goes back to green again (I used 3mm bi-colored LED's with power to both for the yellow indication in a scratch built searchlight target made from brass tubing, wire, and HO scale brass ladder from campbell inds.) ...it worked just like the real thing!....I recommend the Dallee circuits ...besides a 12 volt DC supply, they have a current detector that all that is needed is a wire to pass through them from the rail and back to make them work ...I have one more block to install them in but going to have to wait until i can afford to order more...they're not too terribly expensive, but it's a good thing to keep the credit card to a dull roar...Maybe i can talk my wife into getting me some more for Christmas....chuck

[davekelly]

Cool! Dallee has been around forever and although I've always been interested in their products, have never purchased one. Do you run DC or DCC?

[NZRMac]

That sounds really good Chuck. Will those circuits run three aspect lights?

Hope the exchange rate is in my favour when I need some!!

Ken.

[ereimer]

fantastic !

are you using resistor wheelsets on your rolling stock or just detecting your locos ?

[grayfox1119]

Don't you just love it when a plan comes together?? I think the "A" team used to say that at the end of the show each week.

[cwclark]

ok here's the answers...1. i run DC..too many locomotives to put decoders in...
2. the dallee system can run three aspect signaling,
and 3. I'm only detecting my motors in the locos now but by placing a resistor across the rails (I'll get the rolling stock resistors in at a later date) the only one that works is a 150 or less ohm resistor...chuck

[rrinker]

If it takes a 150 ohm or less resistor, that's not good. At 12 volts, that's nearly 1 watt of power - a resistor like that will not fit on a car axle, and even if it did, it would melt the truck. That's also 80ma per resistor at 150 ohms, a fleet of 50 cars would draw 4 amps just sitting on powered track!
I sure hope you meant 150K ohms.

--Randy

[cwclark]

nope that's what i got...It took a 150 ohm resistor to set off the relay...that was the impression i got too...way too much heat disipated!......that's too small of a resistor ...I tried a 1k and a 580 ohm and it didn't set off the relay either...I have one more to try...a 380 ohm ...I'll play with it tonight when i get home...chuck

[sctroy]

I have been using Dallee detectors for a long, long time - my layout currently has ten of them. Not only can you set them up for three-color signals, but if you add the expansion relay board to turn on/off the common wire to the LED signals, you can make them approach-lit.

The flasher unit also works superbly with a set of working crossbucks.

I set up my signal system originally on DC, and left it in place when I switched to DCC. The Dallee detectors work even better on DCC as you always have maximum voltage flowing to the tracks, With DC, when the throttle was set to zero, the detector wouldn't read anything unless you have a "keep-alive" module added to supply a trickle DC voltage. I've got three "keep alives" if anyone wants them cheap!

Steve Troy

[rrinker]

Even a 1K resistor at 12 volts is more than 1/8 watt. DO you have just one pass of the wire throught he current transformer? Try making a second loop through, this will increase the sensitivity of the detector. Unless they specifically tell you not to do such a thing. The more turns, the greater the sensitivity (high resistence can be detected), at the expense of the maximum current limit. But if it takes a 150 ohm resistor to trip it now, another couple of turns won't kill your upper limit.
A 380 ohm resistor is only going to be marginally better than the 150 ohm - only about 50% better - nearly half a watt so a 380 ohm half watt resistor will get fairly warm.
Check the instructions - there HAS to be some way to make the detector more sensitive. As it is, it's fairly useless for typical block occupency detection.

--Randy

[cwclark]

randy,
I'll give it a try with the second coil of wire..they don't state anything in the book about how many passes it has to make except the one...I gave myself extra wire just in case i'd have to make a second pass....what gets me is that a locomotive just sitting there with the power off sets off the relay but not the smaller resistors...I also have a "keep alive" trickle voltage in the circuit so that's not the problem because the locomotive is being sensed and keeps the Relay in the N/O position...do you think it could be in the power pack ..maybe the newer MRC power packs won't let the shunt in the keep alive component work correctly....chuck

[rolleiman]

QUOTE: Originally posted by cwclark

randy,
I'll give it a try with the second coil of wire..they don't state anything in the book about how many passes it has to make except the one...I gave myself extra wire just in case i'd have to make a second pass....what gets me is that a locomotive just sitting there with the power off sets off the relay but not the smaller resistors...I also have a "keep alive" trickle voltage in the circuit so that's not the problem because the locomotive is being sensed and keeps the Relay in the N/O position...do you think it could be in the power pack ..maybe the newer MRC power packs won't let the shunt in the keep alive component work correctly....chuck

I'm a bit confused too.. I thought the point of current detection for block occupancy was to sense presence of a load (locomotive, resistors on wheelsets, etc).. What is the point of the resistor across the rails?? Is it to increase the sensitivity of the circuit??

With respect to the circuit tripping with a non-running loco, all motors have a current path through them.. What makes them turn (in simplistic terms), as you probably know, is applying an electrical field to the armature that is constantly opposing the field of the perminant magnets.

Jeff

[NZRMac]

The resistor is just for testing.

Ken.

[cwclark]

[#ditto] yes..the resistor was for testing..I haven't installed them on my rolling stock wheel sets as of yet...chuck

[rrinker]

Could be possible that you have no actual voltage in the rails. Check with a meter. It could be realted to the power pack - at the club I used to belong to we had two big packs, an MRC Controlaster 20 and one of those big CMI Hoggers with the walkaround. I built up a ditch light circuit for one of the guys, and it worked great on the old MRC 500 on the bench, and on the CMI line on the layout, but not on the big MRC (by 'working' I mean come on at a low throttle setting before the loco would move). I did a little checking with a meter - it seems the big MRC pack had no pulse component at a very low setting whiel the other units did - enough of a pulse component to operate the ditch light circuit.
Although, if it detects the standing loco, there must be some current flowing. But motor resistence is rather low - especially on a modern loco with a quality motor like an Atlas or Kato or Stewart - which is why you can't control them very well with a classic 50 ohm rheostat.

--Randy

[cwclark]

Randy,
I called DALLEE about the problem with the high resistant resistors and they told me that resistors are not what is supposed to be used...it has to be a .1muf capacitor and it works because i tried it last night.... no heat, and they worked great on the dead siding...the problem is, most capacitors, even the smallest, are too large to fit between the rolling stock wheels...I'm going to have to get a few pairs of conductive pick-up trucks for the rolling stock in the middle of the train and the caboose and mount them in the shells... chuck

[rrinker]

A CAPACITOR? Now that is really odd for a device the claims to be a current detector. Hmm. Just odd to me. Hope you aren't planning to go to DCC, a whole train of cars with capacitors across the rails will wreck the DCC signal.

I was looking at their instructions on the web site and the only mention of a capacitor was one to be hooked up to one of the relay terminals so it is in line with the track supply in place of the pictured ballast lamp, if you are using their keep-alive. Looking at a picture of the keep-alive, I think I know what they are doing, and why a capacitor works, but it all seems a little hokey. Maybe I am getting too used to DCC with power in the rail at all times, but even back in the bad old days, having bypass power to detect stopped trains even for old Twin-T detectors seemed less complicated.

--Randy

[cwclark]

QUOTE: Originally posted by rrinker

A CAPACITOR? Now that is really odd for a device the claims to be a current detector. Hmm. Just odd to me. Hope you aren't planning to go to DCC, a whole train of cars with capacitors across the rails will wreck the DCC signal.

I was looking at their instructions on the web site and the only mention of a capacitor was one to be hooked up to one of the relay terminals so it is in line with the track supply in place of the pictured ballast lamp, if you are using their keep-alive. Looking at a picture of the keep-alive, I think I know what they are doing, and why a capacitor works, but it all seems a little hokey. Maybe I am getting too used to DCC with power in the rail at all times, but even back in the bad old days, having bypass power to detect stopped trains even for old Twin-T detectors seemed less complicated.

--Randy

you got that right!...I could hook up one of those old twin T's with two transistors, a relay ,a terminal strip, and a handful of diodes and resistors...well it does work, and i'm not planning on going to DCC so i'll live with it....the main thing is that it's prototype signaling and that's what counts...thanks for all your input....chuck