sigtech Posted October 24, 2015 Share Posted October 24, 2015 Hello, I have spent the last four days attempting to install a 'BLOCKSIGNALLING' 8 position photoelectric train detector in my hidden sidings. Installing the 8 photoelectric sensors and the associated wiring back to the device was tedious, but reasonably straightforward, then came the 12v leds.... These were purchased from Maplins (8 red and 8 green) - just down the road from me, and fitted into their black plastic holders that have a washer and nut on the end for panel mounting.-so far so good, then came the hard bit!! I already had a small panel made of thin plywood, with two rows of push buttons for operating the Dapol semaphore signals, and had made a small track mimic of the hidden sidings, which fitted just below - as this would save space. I drilled the holes in the panel and fitted the led holders and led's, all that was left was to wire them up and connect to the 'box of tricks'..... Oh dear! three days later and after rewiring all of the leds three times, it still isn't working! I carefully followed the wiring diagram which requires two return paths, one for all the red leds, the second for all the green ones(daisy - chaining them and soldering the wires onto the -tive leg of each led) Next a single wire was run from the other +tive leg of the leds to each appropriate marked terminal on the detector- splaying the legs out so they would not inadvertently make contact,because I needed to access the rear of this panel to connect up more of the signal push buttons later on, so I had to leave some slack into the wiring, no problem I thought... all done and dusted, I carefully "tidied" the wire run with zip ties and refitted the panel. Switch on time, and I was presented with a 'disco effect' any slight movement or tapping resulted in some leds going out , whilst others suddenly lit, any movement of the panel top resulted in the same thing happening- this was not right!! I assumed that the movement of the panel top had "disturbed" the led's, so off came the top and some "tweaking" was done - all to no avail, any movement or disturbance of the wiring produced a flashing light show. I decided I had used too stiff wire - so it all came off and the second attempt followed, but again to no avail... Third try- all the panel wiring was removed and this time I used single strand thin red wire, the sort used in control panel manufacture, surely this would be o.k.?? NO - same thing happened,and I also noticed that the leds occasionally were popping up out from their holders, when pushed back down some lit, some went out, pushing on a led would cause another one to light up or extinguish - this was nonsense.. any movement of the wire also produced this effect. I am now beaten- the leds will all need replacing, and I am no further forward in this project - is there a way to prevent movement of leds /wiring when the panel is removed - HELP!!! Regards SIGTECH (Steve,) Link to post Share on other sites More sharing options...
arff999 Posted October 24, 2015 Share Posted October 24, 2015 Hi Sigtech do you have a link to the unit you are using so i can take a look and also a diagram of how you have it all connected JOHN Link to post Share on other sites More sharing options...
Tricky Dicky Posted October 24, 2015 Share Posted October 24, 2015 Try using the bezels in the following link, you push the LED in first then push the bezel into the mounting hole it has a good interference fit and at the same time locks the LED in, further down are some solderless LED holders these a tight push fit on the LED legs which do have to shortened but you can still identify the cathode of the LED by using the small flat on the bottom rim of the LED. The solderless holder fits inside the bezel. This should solve your movement problem as well as saving a little soldering. http://m.rapidonline.com/Mounts-Holders Richard Link to post Share on other sites More sharing options...
DCB Posted October 24, 2015 Share Posted October 24, 2015 It sounds to me like you got the legs on the LED/resistor combos too hot when you soldered them and loosened them in the plastic so they make intermittent contact. I am forever getting the legs on LEDs too hot and ruining them. You may be better off with standard LEDs and separate resistors. Link to post Share on other sites More sharing options...
Gordon H Posted October 25, 2015 Share Posted October 25, 2015 Why did you choose to use 12V LEDs? Assuming you are using their 'DET-8' unit, nowhere in its information documents does it say you need to use anything other than ordinary LEDs, which is rather remiss of them really not to be more specific. The MAX7219CNG device being used to drive the LEDs runs from a 5V supply, so at best you would see yours very dimly - or as it seems not at all. These driver devices also include a current limiting circuit, meaning you don't need to provide any further resistance in-line with the LEDs attached to it. Suggest you try using a single conventional LED instead, on just one of the channels and see if you can make that work before committing to another complete rewire. Link to post Share on other sites More sharing options...
sigtech Posted October 25, 2015 Author Share Posted October 25, 2015 Hello John sorry about delay in replying- 12 hour shift at work. the link is: http://www.blocksignalling.co.uk/index.php/8-channel-train-detector-det-8 they have an ADOBE pdf file 33DF1L that you can download, which has all the fitting instructions along with circuit diagrams, which I followed. Regards SIGTECH (Steve) Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted October 25, 2015 RMweb Premium Share Posted October 25, 2015 Why did you choose to use 12V LEDs? Assuming you are using their 'DET-8' unit, nowhere in its information documents does it say you need to use anything other than ordinary LEDs, which is rather remiss of them really not to be more specific. The MAX7219CNG device being used to drive the LEDs runs from a 5V supply, so at best you would see yours very dimly - or as it seems not at all. These driver devices also include a current limiting circuit, meaning you don't need to provide any further resistance in-line with the LEDs attached to it. Suggest you try using a single conventional LED instead, on just one of the channels and see if you can make that work before committing to another complete rewire. Looking at the diagram, it certainly does indicate standard LED's. Nor does the documentation appear to specify anything about the LED's. I reckon one standard LED is worth testing with, the worse that will happen is that it will have a very brief & smelly life! The supplier doesn't even appear to sell LED's. As to why the LED's light at all, when moved, maybe the voltage floats high & is enough to cause a flicker? I would suggest the OP contacts the supplier and asks, what type of LED's are recommended. Link to post Share on other sites More sharing options...
RMweb Gold Tony_S Posted October 25, 2015 RMweb Gold Share Posted October 25, 2015 If you look at the data sheet for the led driver device it suggests that only one resistor is needed for all the LEDs connected to the device. I assume that is one one of the resistors on the pcb. Therefore as others have suggested it doesn't need 12 volt LEDs. Link to post Share on other sites More sharing options...
Gordon H Posted October 26, 2015 Share Posted October 26, 2015 Yes, a single resistor is used to set the level of the constant current circuit in the MAX device, but its value won't necessarily be comparable to that used with an LED conventionally as a current limiter. Not only does this device not need 12V LEDs, it won't work very well with them at all - as has been found. Link to post Share on other sites More sharing options...
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