Geoff Cook Posted September 16, 2015 Share Posted September 16, 2015 I had also rewired the power supply to the servos and electromagnets last night. The two are now completely separate. However, the servos still twitch when the magnet buttons are pressed. Has me baffled, only thing I can think of is that the control board is too close to one of the magnets and this is causing some kind of interference? Any ideas? You need to add a 1N4001 diode to each coil to suppress the back emf from the coil it fits across the coil connections with the cathode end, the end marked with the band going to the positive side of the coil supply Have you got any Link to post Share on other sites More sharing options...
Geoff Cook Posted September 16, 2015 Share Posted September 16, 2015 Now that I've managed to fit a DCC chip without blowing anything up I feel qualified to comment on anything electrical. I think your issue is that servos work on small low power signals and electro magnets generate big pulses of magnetic field. The field crossing the servo wiring can in turn induce an electrical pulse which is sufficient to twitch the servo. Long term solution could be some shielding around the electro magnets (bit of lead sheet??) and/or shielded cables to the servos. Obviously this is entirely supposition... When you operate the coils you create the magnetic field' which then collapses when you release the button, this collapsing of the magnetic field creates back emf voltage, the voltage it creates is what is causing the interference, adding a diode short circuits the back emf, Link to post Share on other sites More sharing options...
Geoff Cook Posted September 16, 2015 Share Posted September 16, 2015 Now that I've managed to fit a DCC chip without blowing anything up I feel qualified to comment on anything electrical. I think your issue is that servos work on small low power signals and electro magnets generate big pulses of magnetic field. The field crossing the servo wiring can in turn induce an electrical pulse which is sufficient to twitch the servo. Long term solution could be some shielding around the electro magnets (bit of lead sheet??) and/or shielded cables to the servos. Obviously this is entirely supposition... Shielding the magnetic field won't stop the problem it is the back emf voltage from the coil in the wiring you also need mu metal to shield a magnetic field. if you were to wrap some metal around the coil you would be creating a secondary winding for the coil which is a shorted secondary winding which would burn out the coil Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 16, 2015 Author RMweb Premium Share Posted September 16, 2015 You need to add a 1N4001 diode to each coil to suppress the back emf from the coil it fits across the coil connections with the cathode end, the end marked with the band going to the positive side of the coil supply Have you got any new-2.jpg Thanks for this Geoff and for the subsequent explanation of why it happens, really useful and makes a lot of sense. I don't have any diodes, but will see if I can pick some up either at the weekend or before. Am I correct in thinking that it isn't doing any harm to the servos etc, it's more of an annoyance? In other words - if I don't fix it until after the exhibition am I going to blow anything up!!!! Link to post Share on other sites More sharing options...
Geoff Cook Posted September 16, 2015 Share Posted September 16, 2015 Thanks for this Geoff and for the subsequent explanation of why it happens, really useful and makes a lot of sense. I don't have any diodes, but will see if I can pick some up either at the weekend or before. Am I correct in thinking that it isn't doing any harm to the servos etc, it's more of an annoyance? In other words - if I don't fix it until after the exhibition am I going to blow anything up!!!! It will put unwanted stress on the servo if the twich is driving the servo hard against the limit of travel (the rail ) Link to post Share on other sites More sharing options...
lmsforever Posted September 16, 2015 Share Posted September 16, 2015 The car lot should be Arthur Dayley,s he,s the only person selling classy cars in the UK. Link to post Share on other sites More sharing options...
RMweb Premium 2ManySpams Posted September 16, 2015 RMweb Premium Share Posted September 16, 2015 Shielding the magnetic field won't stop the problem it is the back emf voltage from the coil in the wiring you also need mu metal to shield a magnetic field. if you were to wrap some metal around the coil you would be creating a secondary winding for the coil which is a shorted secondary winding which would burn out the coil Exactly what I thought Geoff Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 16, 2015 Author RMweb Premium Share Posted September 16, 2015 After a visit from Geoff. the twitching servos have been tamed (or more accurately the back EMF from the magnets has been tamed). Big thanks to Geoff for popping round this evening and not only supplying, but also installing the diodes for me - very much appreciated. 5 Link to post Share on other sites More sharing options...
RMweb Premium 2ManySpams Posted September 16, 2015 RMweb Premium Share Posted September 16, 2015 Good man Geoff, glad my sage advice was of use. Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 17, 2015 Author RMweb Premium Share Posted September 17, 2015 Not long now. This time tomorrow the layout will be starting its journey to Aylesbury for Scaleforum. 1 Link to post Share on other sites More sharing options...
Geoff Cook Posted September 17, 2015 Share Posted September 17, 2015 Good man Geoff, glad my sage advice was of use. All your sage advise did, was to get me to do more posts in a day than I usually do in a month. and the man that falls asleep on the stool on his stand thought that your advise was useful, which part I wonder Link to post Share on other sites More sharing options...
RMweb Premium 2ManySpams Posted September 17, 2015 RMweb Premium Share Posted September 17, 2015 All your sage advise did, was to get me to do more posts in a day than I usually do in a month. and the man that falls asleep on the stool on his stand thought that your advise was useful, which part I wonder Glad to see I'm not the only one to have concerns about the man who puts ornaments on his car bonnets. Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted September 17, 2015 RMweb Gold Share Posted September 17, 2015 This is getting personal, I know who you are. Mike. Link to post Share on other sites More sharing options...
RMweb Premium 2ManySpams Posted September 17, 2015 RMweb Premium Share Posted September 17, 2015 This is getting personal, I know who you are. Mike. Just remember that Geoff, Mark and I are trained ninjas. Stealth, cunning and awesomeness are our middle names. Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted September 17, 2015 RMweb Gold Share Posted September 17, 2015 Just remember that Geoff. Mark and I are trained ninjas. Stealth, cunning and awesomeness are our middle names. An I'm a Yorkshireman, tha dunt frit me. Mike. Link to post Share on other sites More sharing options...
RMweb Premium 2ManySpams Posted September 17, 2015 RMweb Premium Share Posted September 17, 2015 An I'm a Yorkshireman, tha dunt frit me. Mike. See you on Sunday... Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 17, 2015 Author RMweb Premium Share Posted September 17, 2015 Should I have booked a van? Link to post Share on other sites More sharing options...
RMweb Premium wagonbasher Posted September 17, 2015 RMweb Premium Share Posted September 17, 2015 Should I have booked a van? If only for the fiddle yards Andy Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 17, 2015 Author RMweb Premium Share Posted September 17, 2015 If only for the fiddle yards Andy Fiddle yards are the least of my worries; its all the tools and materials I'm taking "just in case". Remember first time out with BCB? Think we had enough kit with us the build another layout! Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 17, 2015 Author RMweb Premium Share Posted September 17, 2015 And relax... 1 Link to post Share on other sites More sharing options...
RMweb Premium 2ManySpams Posted September 17, 2015 RMweb Premium Share Posted September 17, 2015 Lager?? Link to post Share on other sites More sharing options...
RMweb Premium Mark Forrest Posted September 17, 2015 Author RMweb Premium Share Posted September 17, 2015 Not my choice, it's Beerbods beer of the week time. Nice though, sort of a cross between an IPA and a lager. 6.2% abv, so just what the doctor ordered. Link to post Share on other sites More sharing options...
RMweb Premium ELTEL Posted September 17, 2015 RMweb Premium Share Posted September 17, 2015 That LAGER looks out of gauge it will make you P4 Link to post Share on other sites More sharing options...
RMweb Premium wagonbasher Posted September 18, 2015 RMweb Premium Share Posted September 18, 2015 That LAGER looks out of gauge it will make you P4 If it is true to scale then the round table Mark has put it on is very small.. Andy Link to post Share on other sites More sharing options...
RMweb Gold Stubby47 Posted September 18, 2015 RMweb Gold Share Posted September 18, 2015 Hope it goes well this weekend. Even without a caravan. Link to post Share on other sites More sharing options...
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