TEAMYAKIMA Posted January 11, 2018 Share Posted January 11, 2018 (edited) I've found a very old ECM capacitor discharge unit which might solve a problem I have with a very stiff device operated by a PECO point motor. The instructions are long gone. It has one set of terminals marked something like ' power in - 24v AC max ' It's 30 odd years since I've used one of these and TBH I'm ashamed to say that I'm not sure how to wire this in, can someone remind me please? Edited January 11, 2018 by TEAMYAKIMA Link to post Share on other sites More sharing options...
Pete the Elaner Posted January 11, 2018 Share Posted January 11, 2018 It looks like the capacitor itself has been disconnected. The AC supply should go the the power in sockets & the other terminals should connect across the motor/switch. Having worked out exactly how a CDU works, I would not operate a solenoid motor without one again. Link to post Share on other sites More sharing options...
RMweb Premium dhjgreen Posted January 11, 2018 RMweb Premium Share Posted January 11, 2018 After 30 years that capacitor will be well down in performance at best. If it is clear how to connect it to the board, a replacement is advised. They dry out and at best lose their capacitance at worst become a short circuit. Link to post Share on other sites More sharing options...
RAF96 Posted January 12, 2018 Share Posted January 12, 2018 I would bin it and biy a new Gaugemaster one which has the poke to throw several points at once. Rob Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted January 12, 2018 RMweb Premium Share Posted January 12, 2018 (edited) It looks like the capacitor itself has been disconnected. The AC supply should go the the power in sockets & the other terminals should connect across the motor/switch. Having worked out exactly how a CDU works, I would not operate a solenoid motor without one again. Here's the typical wiring diagram of a CDU kit. http://www.talkingelectronics.com/projects/CDU-2/CDU-2.html A couple of differences to OP's version. The two wires directly from OP's capacitor are definitely wrong, as OP's bypasses the output diode. I wonder why? This circuit uses 4 low wattage resistors at a higher resistance, compared to your single higher wattage resistor. It of little consequence either way. The explanation is quite could and accurate, but take note in regard the voltage rating of the capacitor(s). This is very important. This kit is available (from Australia - so may not be worth it for you), or buy a new one, as previously suggested. Edited January 12, 2018 by kevinlms Link to post Share on other sites More sharing options...
cpman46 Posted January 12, 2018 Share Posted January 12, 2018 Here's the typical wiring diagram of a CDU kit. http://www.talkingelectronics.com/projects/CDU-2/CDU-2.html A couple of differences to OP's version. The two wires directly from OP's capacitor are definitely wrong, as OP's bypasses the output diode. I wonder why? This circuit uses 4 low wattage resistors at a higher resistance, compared to your single higher wattage resistor. It of little consequence either way. The explanation is quite could and accurate, but take note in regard the voltage rating of the capacitor(s). This is very important. This kit is available (from Australia - so may not be worth it for you), or buy a new one, as previously suggested. I suspect that at some time it's possible a second capacitor was connected across the existing one to give a bigger pulse to the solenoid or solenoids. Link to post Share on other sites More sharing options...
DCB Posted January 12, 2018 Share Posted January 12, 2018 It looks like someone has disconnected the Capacitor from the PCB and and simply used the Capacitor to operate the point motors. These Capacitors are polarity conscious and go bang and spray nasty yellow liquid if over charged (yes I did it) or shorted out so be careful. I just connect a Capacitor across the 12 volt DC uncontrolled output of a transformer, positive to positive etc and use it to power the point motors via a push button however the Cap does need to be at least twice the rated voltage of the Transformers 12 volt DC output as the "12 volt" output is often a lot more than 12 volt off load and can overcharge a Cap quite easily. I find 24 volts provides a bit of a safety margin. I used them 40 years ago on my Triumph and Ariel motorcycles to provide a battery free electrical system, again using 24 volt caps as the proper Lucas 12 volt items were prone to explode. Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted January 12, 2018 RMweb Premium Share Posted January 12, 2018 (edited) It looks like someone has disconnected the Capacitor from the PCB and and simply used the Capacitor to operate the point motors. These Capacitors are polarity conscious and go bang and spray nasty yellow liquid if over charged (yes I did it) or shorted out so be careful. I just connect a Capacitor across the 12 volt DC uncontrolled output of a transformer, positive to positive etc and use it to power the point motors via a push button however the Cap does need to be at least twice the rated voltage of the Transformers 12 volt DC output as the "12 volt" output is often a lot more than 12 volt off load and can overcharge a Cap quite easily. I find 24 volts provides a bit of a safety margin. I used them 40 years ago on my Triumph and Ariel motorcycles to provide a battery free electrical system, again using 24 volt caps as the proper Lucas 12 volt items were prone to explode. But simply putting a capacitor across a DC supply, doesn't turn the solenoid off if the switch (or whatever means to control) fails. The diodes & transistor are there for a reason. Edited January 13, 2018 by kevinlms Link to post Share on other sites More sharing options...
Crosland Posted January 13, 2018 Share Posted January 13, 2018 I just connect a Capacitor across the 12 volt DC uncontrolled output of a transformer, positive to positive etc and use it to power the point motors via a push button however the Cap does need to be at least twice the rated voltage of the Transformers 12 volt DC output as the "12 volt" output is often a lot more than 12 volt off load and can overcharge a Cap quite easily. Yes, we know that you do all sorts of things that should never be recommended to others. Link to post Share on other sites More sharing options...
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