As I am working through installing computer control to my layout, block detection is one of the early key decisions I have to make as I move forward. See my blog entry for the results of my analysis of 4 common approaches.
My blog also chronicles my lessons learned as I begin my second year as a Model Railroader. Still a newbie in the minds of some!
Grace and peace to all!
Joe
Joe,
RE: your rating for IR Detectors.
I know of two IR detectors designed to be placed between the rails like photocells, so they are more concealable. The IRDOT is one, Sensa-Trak, the other.
Those specific products would probably have a little higher rating than the other IRs. Other than that, no quibble with your observations.
Mike Tennent
Thanks MIKE!
I’ll look around and see what I can find about them!
Everything I have seen about IR requires some kind of elevated mount on each side of the track and after thinking about it for awhile, I decided they were not viable.
Appreciate your thinking and input!
Joe
Interesting, but I was expecting something different. To me the decision wasn’t between IR, mangnetic, RFID, or current sensing technology; but WHICH current sensing unit to use. I’ve still trying devise experiments that will show the good and bad qualities of the NCE separate circuit inductance unit vs the in-circuit type used by most everyone else. Then among the others is there one advantage one has over another. For the most part I still use my own twin-T type detectors made with parts from Radio Shack.
Tex,
Your comments are interesting indeed, Lenz (My DCC provider) and CTI (My automation provider) both have detection devices, Lenz uses in-circuit while CTI uses inductance. I have been using the Lenz LR101/LB101 combo for a year, other than complex wiring, no issues. The CTI unit will be tested soon, I’ll let you know if I see issues.
Dig out of the snow yet? We had some powerful melting today.
Joe
Joe, have you tested any ‘home brew’ current detectors? I am talking about the simple ones that consist of a FWB inline with the power to the block and a differential OpAmp hooked up across the FWB. I am looking to get a current based detection system designed for the lowest cost possible.
Evening Dave,
I visited your website, hand not thought about series and parallel dc circuits specifically for a long time. I’ll keep the link handy next time I need to find a resistor value. Nice work.
I don’t know what you mean by FWB, and quick google did not help me either.
Best regards,
Joe
Sorry, Navy terminology still slips out. FWB = Full Wave Bridge Rectifier.
I still slip every now and then and refer to things as Bulkhead and Deck. My wife makes fun of me every time.
Texas Zepher,
Are you talking about the NEC detector that you loop one feeder wire through? I’d be interested in your observations. I’ve got a few of them, but haven’t had a chance to set them up on my new layout.
I do recall when they first came out that some folks voiced concern that resistance in the track itself would make them too sensitive in long blocks, but never saw any hard evidence of this.
Have you used them for a while?
Mike Tennent
Mike
I did some reading on the Sensa-trak device as their website. Interestingly the product is almost as expensive as block detection 8 vs 10 bucks, relies upon ambient light, which means it will not work in the dark and of course it is a spot sensor. While I think they overcome the issues with installation, they loose much of value of the infrared capability by using ambient light. My 2 cents worth of observation. [:)]
Thanks for pointing this out to me!
Joe
Hi Folks,
Our club ( BSME.org ) has been using the NCE detector for about 2 1/2 years now with very little trouble at all. I have them hooked to a Radio Shack relay to provide us with a red/green block signal system. It has been just about bullet-proof and if they were going to break down, we would find a way. Our longest block is somewhere near 15 to 20 feet. We use about 12 of these devices on our layout.
We bought the NCE detectors a couple of years ago for about $11 each when they were on sale thru MicroMark. I think the relay cost about $4.
What would the next step be to hook them up to LocoNet and send that information to our copy of DecoderPro?
As I understand in your post, in addition to block detection you are also installing computer control. I too am using the Lenz Set 100 combined with LB101, LR101, LS100, and LS150 modules and accessory decoders, UBB Computer interface and the Railroad & Co. v5.5 Train Controller software. I have a total of 24 monitored blocks which allows me to both monitor and control all train movements on my on-screen schematic via my PC including turnout control. Also, using the LS100 accessory decoders http://www.lenz.com/products/decoders/accessory/ls110v2.2.htm I can automate my trackside signals to indicate occupancy or vacancy. All detection is based on the current sensing principle and is therefore not dependent on lighting conditions, sensors or reed switches between the rails. A good source for Lenz and other DCC products and information is Tony’s Trains http://www.tonystrains.com/
Because you need to create blocks using the LB101 block occupancy detectors combined with LR101 feedback modules if you plan compute
Steff,
My original intent was to go in the direction you have taken. I have 16 blocks of LR101/lb101 operational. I looked at and evaluated RR & CO and found it to be much too expensive and not that much ‘better’ than the other products I had looked at. (After a few days of frustration with the Demo I abandoned it.
Further, the premier signalling systems I have seen were C/MRI and CTI. C/MRI was very expensive and complex. The CTI software and hardware was easy for me to understand and make things happen with it. I remain convinced that except for some unique applications, current flow block detection is an optimum solution. I wish that CTI would make their software talk to the DCC feedback circuits. Perhaps they will soon.
I liked your circuit panel. I have my equipment in a drawer. And thank yo for sharing with your informative post!
Joe
Block Occupancy Article - NMRA Bulletin, March 2001 (pg 46)
My UP and Western Railroad http://bobfrey.auclair.com now uses 5 Digitrax DCC boosters. This low cost current detection circuit, with 100K Isolation, solved my DC logic SIGNAL COMMON problem. As you know, the DCC boosters where the track power is connected, must be isolated from an adjacent booster.
With DCC train control, there are two wires with AC power applied to each track and a common bus between all boosters. If signaling is going to be used, then there is a need for isolation between blocks, booster, control bus and the SIGNAL COMMON. Thus occupancy circuit isolation has been generally done in the form of relay contacts, opto-isolators, or current-sensing pulse-transformers inputs. Another form of isolation is the Block Occupancy Circuit of Fig. 1 with 100K resistance Isolation. Even with +/- 40 Volts applied between the Block side and the SIGNAL side there is no operation.
To obtain an operation, a track current greater that +/- 1 ma. must flow through the diodes D1 or D2. This will produce a voltage across capacitor C1 that can be amplified to produce a DC current through the LED and operate the power transistor Q5 for a steady state output. The output remains ON for about 3 or 4 seconds after the track current is removed. Only a very small amount of current actually leaks through the 100K isolation resistor R1 during operation. The DC power for this block occupancy detector does not have to be regulated. Even rectified power with no filter can be used as a DC supply.
After completion of the circuit, the operation can be checked by using a 9-Volt battery as a DC supply and another 9-Volt battery with a 1 K resistor as the input block current of +/- 9 ma. The LED must light when this current is applied in
Yes.
No, I am just like you. I’ve got a box of them (and other brands) sitting here. I bought them as an experiment about 18 months ago, but I haven’t been able to find time to do anything with. That is why I was hoping someone else had some obervations.
These folks?
http://www.cti-electronics.com/dcc.htm
I had never heard of them before.
Yeah, we were never snowed in. The worst part was having to dig a path in the back yard for the dogs (big dogs) to get out and do their business. I only have 1 non 4-wheel drive vehicle so we have been running all over even during the storms proper. But we still shoveled out into the street so when the sun hit it our driveway and the street infront of the house were dry by Christmas. Our big problem is that the city decided the best place for them to pile snow is right next to us. So now all the kids in the neighborhood come over to sled on the snow mountain (it has to be about 15 feet tall). They knock snow off the top into our cleared area so the sleds don’t come to an abrupt stop when they hit our dry spot.