RMweb Gold Colin_McLeod Posted October 30, 2009 RMweb Gold Share Posted October 30, 2009 My layout runs with ZTC DCC equipment and I am aware that there is no feedback facility to send signals to the command unit. My layout has two sections of track that run almost entirely in tunnel and they link the continuous run to the storage sidings. Does anyone here know of a simple track occupancy circuit that would be DCC compatible that I could install on these two sections of track that would operate an LED when the track is occupied? I don??™t want to purchase any expensive track occupancy module as I am not looking for any sophisticated control, merely to illuminate an LED if there is a ???Train in Section???. I was thinking of some kind of device that would detect the motor circuit, or detect a current flowing. The circuit would have to operate even if the train was stationery. There would always be a locomotive present on every train. The two sections of track are completely electrically isolated from the remainder of the layout. Thanks Colin Link to comment Share on other sites More sharing options...
Miss Prism Posted October 30, 2009 Share Posted October 30, 2009 There are some DCC block occupancy circuits in http://home.cogeco.ca/~rpaisley4/CircuitIndex.html#REVISION Link to comment Share on other sites More sharing options...
two tone green Posted October 30, 2009 Share Posted October 30, 2009 I seem to remember that the Lenz LB101 can do this. The 'internal switch' can be used to operate a LED as you want. Also as one LB101 has two detectors on it, you only need one unit in your case. Gordon has some for sale at ??10 each. If it works, saves having to build any thing. Will try to find the set up for it to do this on line but I will need to search a bit as it is a long time ago since I saw it. Link to comment Share on other sites More sharing options...
GoingUnderground Posted October 30, 2009 Share Posted October 30, 2009 There was a design in continental Modeller aout 2-3 years ago, sorry, can't remember which edition, which included instruction for self-build detectors for about ??1 each. They were fully electrically isolated from the DCC circuit, so you could use them with a simple indicator lamp or LED circuit. Link to comment Share on other sites More sharing options...
Nigelcliffe Posted October 30, 2009 Share Posted October 30, 2009 Current sensing: MERG have a nice kit for occupancy using current detection. It could illuminate some LEDs or similar. It comes as 8-detectors in the kit, which can be split into four double-connectors. Reported to be able to detect a finger on the track, or the smallest decoders going. Kit around ??22, plus MERG membership. I think the Lenz LB101 may do what you want; it has two detectors and two outputs and is only ??15 or thereabouts. Manual only describes using it to drive more Lenz kit, but I think it could drive something else such as LEDs, relay, etc. Beam breaking: Could use an IR based beam-breaking detector, such as those from Heathcote Electronics IRDOT or IRDOT-1D; lights up when train breaks the beam. Link to comment Share on other sites More sharing options...
BromsMods Posted October 30, 2009 Share Posted October 30, 2009 There are also other IR systems, e.g. Logic Rail - see http://www.bromsgrovemodels.co.uk/pi1241702312.htm?categoryId=52 Link to comment Share on other sites More sharing options...
RMweb Gold traction Posted October 30, 2009 RMweb Gold Share Posted October 30, 2009 You could use the IRODT's from Heathcote electronics, I know they don't measure the current but they do work well. The IRDOT 1D has an undetect delay on it so the panel mounted LED won't flicker from the gaps between the coaches/wagons. Cheap and cheerful solution. Link below http://www.heathcote...ec.htm#IRDOT-1D Link to comment Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted October 30, 2009 Author RMweb Gold Share Posted October 30, 2009 I'm overwhelemed at the number of replies. Many thaks everyone. The RMWeb community is obviously still alive and well. The tracks in question are quite long; much longer than a train; so the Lenz or similar option seems appropriate. I appreciate the IR suggestions, but they only detect a train when it is at a certain position. I think the Lenz LB101 option may be the way to go as I don't want to risk damaging my DCC equipment with a home made circuit gone wrong. (may invalidate the guarantee LOL) Nigelcliff says that the manual only describes using it to drive more Lenz kit, so I may be depending on Two Tone Green's set up if he can find it. (Thanks in advance TTG) Colin Link to comment Share on other sites More sharing options...
two tone green Posted October 30, 2009 Share Posted October 30, 2009 Hi Colin, so far nothing. I know it was from many a year ago seeing it on some ones web page about using LED's on a panel to show occupancy as you want to do. In fact I think they were LB100's then. It was even before RM WEB flavour 1 so may not even be around any more. But I think the internal 'switch' would handle the low power draw of a LED. I don't have any spare to try as all 14 of mine are on my test layout in Bristol and I am home suffering with Swine Flu. I agree about the IR devises though as they are the same as a reed switch and act as a spot detector rather than a block occupancy detector which is what you need for the added protection on hidden tracks. Wil keep looking. TTG Link to comment Share on other sites More sharing options...
PhilC Posted October 30, 2009 Share Posted October 30, 2009 Is this the drawing...Don't know if it works Cheers Link to comment Share on other sites More sharing options...
GoingUnderground Posted October 30, 2009 Share Posted October 30, 2009 The one in Continental Modeller worked on current sensing. I took a copy, i'll see if i can find it. Link to comment Share on other sites More sharing options...
two tone green Posted October 30, 2009 Share Posted October 30, 2009 Yes, could well be the circuit as all the switch does is put it to ground. The same as using it with the LR101. Link to comment Share on other sites More sharing options...
Nigelcliffe Posted October 30, 2009 Share Posted October 30, 2009 There is a chap with some s/hand LR101's for sale in the Yahoo "DCCUK" group. He's asking ??10 each plus postage. Link to comment Share on other sites More sharing options...
two tone green Posted October 31, 2009 Share Posted October 31, 2009 Its Gordon S off here and I think they are LB101's. The item Colin is after. Link to comment Share on other sites More sharing options...
gordon s Posted October 31, 2009 Share Posted October 31, 2009 Yup, that's me trying an alternative route to market....Two will be on their way to Colin on Monday. Many thanks for alerting Colin. Link to comment Share on other sites More sharing options...
two tone green Posted October 31, 2009 Share Posted October 31, 2009 10% commission please Link to comment Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted October 31, 2009 Author RMweb Gold Share Posted October 31, 2009 I was going to say that I had been in contact with Gordon and that the Lenz equipment was on its way, but Gordon beat me to it. Many thanks again to everyone for the suggestions and the circuit diagram. Colin Link to comment Share on other sites More sharing options...
TartanTrax Posted October 31, 2009 Share Posted October 31, 2009 The one in Continental Modeller worked on current sensing. I took a copy, i'll see if i can find it. Hi All, The article referred to here I believe was one of ours. We used an opto-isolator and 4 diodes for short-circuit protection. The diodes are arranged with two in series in one direction and the other two in series pointing in the opposite direction but connected in parallel to the first two . The current rating of the diodes should be around half the current rating for your booster. However if all you want is to light a LED, you could use three diodes and one LED. Two diodes again in series allowing current in one direction, the third diode in parallel to these allowing the current to flow in the opposite direction and finally your LED connected again in parallel but facing the SAME way as the two diodes in series. It should be dirt cheap and perfectly safe. Best wishes, Tartan Trax Link to comment Share on other sites More sharing options...
Gordon H Posted October 31, 2009 Share Posted October 31, 2009 I think the Lenz LB101 option may be the way to go as I don't want to risk damaging my DCC equipment with a home made circuit gone wrong. (may invalidate the guarantee LOL) The MERG design in question is very unlikely to cause any damage to your DCC equipment because it is completely isolated from it. Your track feed wire simply passes through the hole in the current sensor without being connected to it. If anything, other methods which require you to make actual connections to the track have more chance of causing problems. Another benefit is that because only a short piece of wire is involved there are no voltage drop issues, unlike methods which use diodes in series with the feed. Link to comment Share on other sites More sharing options...
jmg123 Posted October 31, 2009 Share Posted October 31, 2009 Here is a page from the nmra on it a bridge rectifier and a pair of led's should do the trick, and cost about 50p Link to comment Share on other sites More sharing options...
RMweb Premium PaulCheffus Posted November 6, 2009 RMweb Premium Share Posted November 6, 2009 Current sensing: MERG have a nice kit for occupancy using current detection. It could illuminate some LEDs or similar. It comes as 8-detectors in the kit, which can be split into four double-connectors. Reported to be able to detect a finger on the track, or the smallest decoders going. Kit around ??22, plus MERG membership. I think the Lenz LB101 may do what you want; it has two detectors and two outputs and is only ??15 or thereabouts. Manual only describes using it to drive more Lenz kit, but I think it could drive something else such as LEDs, relay, etc. Beam breaking: Could use an IR based beam-breaking detector, such as those from Heathcote Electronics IRDOT or IRDOT-1D; lights up when train breaks the beam. Hi Even cheaper from MERG is the ToTI (about ??5 for four sections) and yes it does work on DCC. Cheers Paul Link to comment Share on other sites More sharing options...
Suzie Posted November 9, 2009 Share Posted November 9, 2009 ? ? However if all you want is to light a LED, you could use three diodes and one LED. Two diodes again in series allowing current in one direction, the third diode in parallel to these allowing the current to flow in the opposite direction and finally your LED connected again in parallel but facing the SAME way as the two diodes in series. It should be dirt cheap and perfectly safe. You might like to have two diodes each way (rather than one one way and two the other) to avoid creating an asymmetric waveform. Some decoders will stop the train when they see an asymmetric waveform. This method really works best with red LEDs because they have a lower forward voltage drop, other colours may not light fully. The MERG detectors will be a bit more work to build but they are less intrusive and can be tuned easily for whatever sensitivity you require. Suzie x Link to comment Share on other sites More sharing options...
Crosland Posted November 9, 2009 Share Posted November 9, 2009 ? You might like to have two diodes each way (rather than one one way and two the other) to avoid creating an asymmetric waveform. Some decoders will stop the train when they see an asymmetric waveform. This method really works best with red LEDs because they have a lower forward voltage drop, other colours may not light fully. You will only get an asynchronous waveform if the diodes are in series with the track feed. The suggestion was to use diodes across the track, two to drop enough voltage to drive the LED, one to protect the LED against reverse voltage. The crucial point is that you need a current limit resistor in series with the LED/diode arrangement. Andrew Crosland Link to comment Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 9, 2009 RMweb Gold Share Posted November 9, 2009 You will only get an asynchronous waveform if the diodes are in series with the track feed. The suggestion was to use diodes across the track, two to drop enough voltage to drive the LED, one to protect the LED against reverse voltage. The crucial point is that you need a current limit resistor in series with the LED/diode arrangement. Andrew Crosland Andrew, the diagram shows the diode and LED arrangement in one of the track feed wires rather than across the rails. No current limiting resistor is required as the LED is in parallel with a pair of diodes. The diodes each produce a voltage drop of 0.7 volts so the LED can only see a maximum of 1.4 volts. Heavy current flows through the diodes, the LED is only carrying enough current to cause it to light. I use a very similar circuit on bith Dagworth and Ravensclyffe except the LED is one side of an opto-isolator, the output of the opto is then fed into a pulse stretcher circuit based around a 74HC123. Andi Link to comment Share on other sites More sharing options...
Etched Pixels Posted November 9, 2009 Share Posted November 9, 2009 Before you spend a vast amount don't overlook the sometimes obvious. For the price of some of these infra-red sensor kits (espeically in pairs), or fancy current sensors you can pick up a crappy remote or (if you have a PC for the layout) USB camera and some LED lights. Beats detector LEDs hands down. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.