bossy Posted July 19, 2016 Share Posted July 19, 2016 Have a couple of old circuit boards that have input from the point switch (standard peco point motors connected to high capacitor) with out puts to red and green indicator led's. the boards are powered by 12 or 16v. So switching a point and led changes to the red or green indicator. Problem I have is changing a point is now causing other led indicators to change on the other points and they start flashing some times. I have disconnected the capacitor and it appears to have helkped. Thinking I am getting some feedback as the boards appear to be very sensitive. I don't know which make they are but about 7yrs old and how they work. Thinking a diode or something but my electronics knowledge is zero and would not know where to even try to put them. Any help appreciated Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted July 20, 2016 RMweb Premium Share Posted July 20, 2016 When you say 12 or 16 Volts, what sort of power are you connecting. I would suggest that you need a regulated power supply, given the nature of the problem and put the capcitor back in circuit, unless it was an add on connected by you! Link to post Share on other sites More sharing options...
knitpick Posted July 20, 2016 Share Posted July 20, 2016 Sorry, but I find your query confusing. Do you have a separate circuit board (controlling LEDs) for each point? Or does on board control the indicating LEDs for a number of points? You say the input is from the point switch - do you mean an auxiliary switch attached to the Peco point motors (the default Peco point motors don't have auxiliary switches attached)? Or do you mean attached to the point motor coils themselves? Is the LED controlling circuit board powered completely separately from the point switching capacitor circuit. I.e. separate Transformer / separate transformer winding? If the circuits are completely separated but a circuit board controls more than one set of LEDs then the issue must lie within the circuit boards - and you will need to go back to the supplier. Otherwise, as you suggest, there could be a cross feed. To be honest, I would keep the two circuits electronically separated - I.e. separate transformers and using auxiliary switches. Link to post Share on other sites More sharing options...
bossy Posted July 20, 2016 Author Share Posted July 20, 2016 Sorry, but I find your query confusing. Do you have a separate circuit board (controlling LEDs) for each point? Or does on board control the indicating LEDs for a number of points? You say the input is from the point switch - do you mean an auxiliary switch attached to the Peco point motors (the default Peco point motors don't have auxiliary switches attached)? Or do you mean attached to the point motor coils themselves? Is the LED controlling circuit board powered completely separately from the point switching capacitor circuit. I.e. separate Transformer / separate transformer winding? If the circuits are completely separated but a circuit board controls more than one set of LEDs then the issue must lie within the circuit boards - and you will need to go back to the supplier. Otherwise, as you suggest, there could be a cross feed. To be honest, I would keep the two circuits electronically separated - I.e. separate transformers and using auxiliary switches. Hi, Sorry I will explain better. I have a circuit board not sure which make quite old and I lost the instructions!.. it is powered from a 16v AC output of an old controller and has the facility to indicate the lever position of 4 points. The board has connections one side for the wires directly to one green and one red LED ie. 4 sets in total. The other side is another set of inputs from the point levers (using peco pl type). So you connect up the peco point motor to the switches as normal the take two wires from the point switch ie level switch to the board (as I call it) so that when you change the point the led is either red or green. Obviously it does not really tell you if the point has actually switched as its picking up from the point lever. However I have noticed that if you disconnect the peco point motor feed the led stop working!! ie I was thinking you could connect the board up with the led's and just move the level without actually being connected to the peco point motor and see the leds change but they don't....... I am thinking feedback from the point change capacitor or something. or worst I have a small short on one of the point motors which is going to major as I cant get at some...... the middle statement makes me think its all linked........ Link to post Share on other sites More sharing options...
Il Grifone Posted July 21, 2016 Share Posted July 21, 2016 This is rather difficult without knowing the actual circuit. I would assume that each pair of LEDs is driven by a bi-stable (either discrete components or an I.C.) triggered by the impulses from the point lever switch and that possibly there is a circuit that detects the presence of the point motor coils to avoid unused LEDs illuminating. Since this is fairly straightforward, my first thoughts would be faulty smoothing/decoupling capacitors or conductive contamination of the board. Does the same thing happen if you use a different pair of LEDS? A photo of both sides of the board might help. Intermittent faults are always the hardest to diagnose. Link to post Share on other sites More sharing options...
knitpick Posted July 21, 2016 Share Posted July 21, 2016 As Il Grifone notes, it is difficult to diagnose without quite full details of the circuit. However, I go back to your answer to my previous post. Are you using the same 16vAC supply for both these indicator circuits and for the CDU (Capacitor Discharge Unit)? Your comment about what happens when you disconnect the Capacitor suggests that you are. I would strongly recommend using a separate supply to charge the CDU. Otherwise there could be other interconnections between the wires to / from the circuit boards and the CDU circuit (e.g. wires shorting in a plug / socket?) Link to post Share on other sites More sharing options...
bossy Posted July 26, 2016 Author Share Posted July 26, 2016 thanks for reply's. I have disconnected power feed to all points and removed LED connections to all but 2 point sets but still get one of the other point led alter when changing the remaining point. The indicator wires from the board I have connected to the physical hand switch to detect the change.. The board is old so it may be 12v DC only so me thinking if that could be problem so going to try this. Also I may have mixed up +/- terminals that I assume may also be an issue Just about to dump the lot and install micro switches as its now been 3 weekends messing with this lot. I noticed today that you can still purchase the point indicator boards look a little more modern. I actually have 2 boards indicating 4 points each and both are playing up. Link to post Share on other sites More sharing options...
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