Hi guys,
As usual, I made a purchase without asking anyone about it but anyway, I purchased 6 train detection circuits from www.dallee.com (click under “signaling and automation equipment” and then click " basic detector") …I was fascinated with the way these type of detector’s work…it has a built in current flow detector and looks to be real easy to wire …What I would like to know is, has anyone ever used the Dallee TDC before and was it a good circuit, and would also like your opinion of what y’all think about it if it’s the first time you’ve seen a device like this…chuck
I have one in the ‘sample’ box here. They make some pretty wild claims, which are totally outlandish, but hey, thats what marketting is about right! In fact the unit is very sound and as you say is easy to wire. They work quite well on the typical American prototype loco’s from the American manufacturers. On ‘N’ scale I found I had to use two turns of wire through the sensor.
My oly problem with it is that of size, it is VERY large! My layouts are built on a hollow core table-top (from Ikea) which is like a hollow core door, with extruded foam over that and any electronics like this is actually buried in the foam. The foam is loosely attached to the table-top, so I can actually lift the entire foam piece which supports the layout and thus reach the electronics if I ever need to. This means I need very low profile electronics.
So I ended up designing and making my own. Without a relay they are all of about 4mm thick. I don’t need a relay as I feed the signal back to a controller.
Seems ok, but rather large. Current transformer method is the best detection - if you use the diode drop type and have undetected blocks, you need to install diodes there to keep the voltages even.
Check Rob Paisley’s web site, his detectors also use the current transformer and run about 1/4 the cost per block - and are much smaller. You’d have to add your own relay if you need to drive high current loads, but for input to an electronic signalling system, or just to light up some LEDs, they work great as-is.
–Randy
Bear in mind that if your locomotive is stopped, this type of detector will decide that the block is unoccupied.
As I recall: Dallee’s system uses relay’s which detect running engines, not with the power off - such as a train stopped at a station, or a passing siding. He has a device that supplies a ‘trickle curret’ for each block to keep the relay’s locked down - at an additional cost per block…
His system does not require ‘Common Rail’ wiring to work, just a minimal amount of current within the block. to trigger his relay’s.
The one mentioned shows as a simple current transformer design, so there needs to be some current flow to be detected. Not an issue with DCC and a few resistor wheelsets and/or lighted cars. They may still have anotherone that uses the old method of a series relay coil to do the detection - in the 50’s they were all the rage, several vendors sold appropriate relays, even Tru-Scale. The Twin-T sort of did away witht he relay systems, and more recently, diode-drop and current transformer methods seem to be the most often used.
–Randy