ejstubbs Posted October 4, 2016 Share Posted October 4, 2016 I feel that this is a very basic question, but I've so far failed to find a clear answer. If I want to work two solenoid point motors off one switch - say for a crossover - is it better to wire them in series or in parallel? Assume that: the point motors will be driven from a CDU all wiring & switch gear is plenty man enough for the job cable runs are relatively short - no more than 3m the points themselves move freely (pace the overcentre spring) and the motors have been correctly installed ie there aren't any unnecessary mechanical losses. AIUI the purpose of a CDU is to provide a large reservoir of charge to dump through solenoid(s) so I would have thought, in my simplistic little way, that you'd want all that charge to go through both - hence wire them in parallel. I think that if you put the solenoids in parallel then the current will be split between them, whereas in series the same current will pass through both. However, if wiring them in series halves the potential across each coil then the current flowing through each will be halved. So do the two factors more or less cancel each other out, and it doesn't matter? (I've never been very confident about how inductance works - does it show?) Basically: I'm a bit thick about this, so what's regarded as "best practice", and why? Link to post Share on other sites More sharing options...
RMweb Premium kevinlms Posted October 4, 2016 RMweb Premium Share Posted October 4, 2016 Definitely wire them in parallel. You want the full voltage available. Link to post Share on other sites More sharing options...
RMweb Gold Phil Bullock Posted October 4, 2016 RMweb Gold Share Posted October 4, 2016 Agree with in parallel Have run up to 6 in parallel using a diode matrix and 1N4001 diodes for route setting with a CDU Phil Link to post Share on other sites More sharing options...
Suzie Posted October 4, 2016 Share Posted October 4, 2016 Best is to fire them sequentially with a 2-second gap between, or use two separate CDUs Link to post Share on other sites More sharing options...
Signaller69 Posted October 4, 2016 Share Posted October 4, 2016 Not had any problem wiring cross-overs (pairs of Peco Streamline points) in series with Peco or Seep motors when using a CDU. HTH. Martyn. Link to post Share on other sites More sharing options...
ejstubbs Posted October 4, 2016 Author Share Posted October 4, 2016 Do'h, I thought at first we were heading towards a consensus, but now there's been a dissenting voice! Maybe it doesn't really matter... Best is to fire them sequentially with a 2-second gap between I'm sure that would be another way of doing it, but it sounds like it would involve additional electrickery-ness to implement the sequencing. I believe that's something you're comfortable with, but in my case I've forgotten pretty much everything I learned about that sort of stuff at uni and can only really cope with what I picked up from this excellent tome way back in the 1960s! Link to post Share on other sites More sharing options...
28XX Posted October 4, 2016 Share Posted October 4, 2016 Tried this on Saturday with Triang lever switches, doesn't work. I know about the redundant pulse at the beginning of lever stroke (A and E positions on the real railway). Next step is to try a bigger CDU. Link to post Share on other sites More sharing options...
28XX Posted October 4, 2016 Share Posted October 4, 2016 As regards why? Magneto Motive Force = I x N. the current x the number of turns in the coil. With an ideal CDU, switches and cabling with zero internal resistance, the current flowing in each parallel coil would be limited only by the impedance of the coils, which is what we want. Link to post Share on other sites More sharing options...
Signaller69 Posted October 4, 2016 Share Posted October 4, 2016 Do'h, I thought at first we were heading towards a consensus, but now there's been a dissenting voice! Just to clarify and add to my post above, I have had no issues with wiring a cross over to throw 2 point motors together via a CDU and one switch, so they are technically in parallel with power flowing through 2 coils (1 in each motor) simultaneously. Quite simply it was done as an economy of wiring measure across board joints. They don't have the same "whack" when thrown over as a single motor, BUT they do throw reliably which was the point I was making (pun intended!). Editted to correct my confusion. Link to post Share on other sites More sharing options...
Brian Posted October 5, 2016 Share Posted October 5, 2016 Hi Do you really mean the two motor coils are in Series? i.e. Series would be.... Feed/supply to motor 1 coil 1, other end of coil 1 connects to other point motors coil and the other end of that coil connects back to supply. This would only possible where the two coils of a motor are separately taken out to four connection terminals per motor. Seep PM range couldn't be series wired as both coils share the one return connection tab nor could any surface style motors - Peco PL11 etc I feel you may mean in Parallel? i.e. You link point motor 1 Normal coil to motor 2 Normal coil and the same with the two Reverse coils One pair of operation wires for Normal and Reverse come from the operating lever or switch and runs out to the first motor, then the wiring links onto the second motor. Returns connect together and go back to the CDU or supply. Largest problem is if the second point motor is some distance from the fist. As the first tends to 'grab' all the power before it reaches motor 2 often resulting in one motor moving and the other failing or only partially moving. Ideally the best option is to run four operation wires from the one operating lever or switch and keep all wires as near as possible to the same length and they are of at least 16/0.2mm equipment wire size or larger. Then each motor should receive as near as possible an equal amount of power. Edit to correct typo! Link to post Share on other sites More sharing options...
Signaller69 Posted October 5, 2016 Share Posted October 5, 2016 Hi Do you really mean the two motor coils are in Series? i.e. Series would be.... Feed/supply to motor 1 coil 1, other end of coil 1 connects to other point motors coil and the other end of that coil connects back to supply. This would only possible where the two coils of a motor are separately taken out to four connection terminals per motor. Seep PM range couldn't be series wired as both coils share the one return connection tab nor could any surface style motors - Peco PL11 etc I feel you may mean in Parallel? But you link point motor 1 Normal coil to motor 2 Normal coil and the same with the two Reverse coils i.e. Only one pair of operation wires for Normal and Reverse come from the operating lever or switch and runs out to the first motor, then the wiring links onto the second motor. Returns connect together and go back to the CDU or supply. Largest problem is if the second point motor is some distance from the fist. As the first tends to 'grab' all the power before it reaches motor 2 often resulting in one motor moving and the other failing or only partially moving. Ideally the best option is to run four operation wires from the one operating lever or switch and keep all wires as near as possible to the same length and they are of at least 16/0.2mm equipment wire size or larger. Then each motor should receive as near as possible an equal amount of power. Edit to correct typo! Yes you are absolutely correct Brian, slight confusion on my part possibly, one switch fires two motors via the CDU, the motors being only around 12" apart with one coil feed on motor A being directly linked to the opposite coil feed on motor B, with the return feeds running to a common return so by that definition they are parallel rather than series. Martyn. Earlier post editted to reflect this post. Link to post Share on other sites More sharing options...
ejstubbs Posted October 5, 2016 Author Share Posted October 5, 2016 I do know the difference between series and parallel! I did not know that some point motors do not readily* allow connection in series, so thanks for pointing that out. That does, of course, render the question somewhat moot if you choose to use one of those types of point motor. It also suggests that manufacturers regard parallel wiring as being pretty much standard practice (assuming they give any thought to the matter at all). The Peco PL10 series point motors do provide a separate return terminal for each coil, so can be wired in series if that's what one wanted to do. (Arguably this also means that they can too easily be wired in series by mistake.) * It is possible to wire two PM point motors in series using a DPDT switch, but it would seem to be a little perverse. Link to post Share on other sites More sharing options...
Suzie Posted October 5, 2016 Share Posted October 5, 2016 With series connection you are going to get about a quarter of the peak power, and all the energy delivered to the motors (eventually). With parallel connection you will get about half the peak power and half the energy delivered to each motor. What is best for you if using either of these methods is down to how much power is required to move your points - if sticky the parallel method will be best, but you will probably need a bigger CDU that will apply too much power to single motors, otherwise the series method will be best. Using multiple CDUs which are correctly sized for a single motor will ensure even power application. Here is how to wire multiple CDUs:- You can divide your non-crossover points over the two CDUs by connecting them to either the blue or purple common wires. I have used the twin CDU method where fiddle yards have the points at both ends fired together. This saved having to build special big CDUs and having a very fat common wire the length of the fiddle yard. Link to post Share on other sites More sharing options...
stewartingram Posted October 5, 2016 Share Posted October 5, 2016 Simple Ohms Law (or basic electrics). A supply of 12v fed to a single coil means 12v to operate the coil. Put another coil in parallel, ie red wire to the same position on each coil, blue wire to the same (opposite end) position on each coil, there is still 12v available to each coil. However the available energy to each coil is less - ie less punch to operate them. (Assuming the psu is of limited power as most are) Wire them in series - red wire to the 1st coil, green wire joins the other end of the 1st coil to the beginning of the 2nd coil, then blue wire from the end of the 2nd coil back to the psu - you only get 6v available at each point motor. (Wire colours and voltage are chosen at random for description only). Introduce a cdu between the psu and coil, you get a more concentrated punch of energy due to the internals of the cdu wiring. Hence the multiple wired coils work better. Best to keep to parallel wiring though to ensure a higher voltage at each coil. Stewart Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted October 5, 2016 RMweb Premium Share Posted October 5, 2016 A bit of basic guff about solenoids and CDUs A solenoid point motor requires a lot of current to operate ( say 4Amps plus ) but the amount of current required would destroy it if was continuous. (cue smoke & flames!) They can be operated from AC or DC. There are two main ways of operating them. Using a power supply large enough to supply the operating current (AC or DC) but you must use momentary switches (stud contact, passing contact etc.) to obviate the chance of burning them out. Using a CDU, which is a low power DC supply but with a large reservoir of energy storage (the capacitors in the name) Much less chance of burn out as the continuous current available is quite low. CDUs are a convenient way to operate them and are widely available from many manufacturers, generally speaking the more storage there is (capacitors) the more reliable operation there will be. A decent CDU should operate two solenoids in parallel without a problem (personally I would not series wire them!) In the past I have driven such beasts as H&M point motors from a large AC supply with Triacs to switch them but that's a bit over the top! Cheers Keith Link to post Share on other sites More sharing options...
28XX Posted October 5, 2016 Share Posted October 5, 2016 Susie. Thanks. This will fix my problem. Link to post Share on other sites More sharing options...
Crosland Posted October 6, 2016 Share Posted October 6, 2016 Best to keep to series wiring though to ensure a higher voltage at each coil. Stewart Wrong way round. Parallel wiring gives the highest voltage at each coil. Andrew Link to post Share on other sites More sharing options...
Crosland Posted October 6, 2016 Share Posted October 6, 2016 A bit of basic guff about solenoids and CDUs A bit more... The energy stored in the CDU capacitors is proportional to the capacitance and to the square of the voltage. You get quite a good increase in "ooomph" from a modest increase in voltage. E.g. going from 12V to 15V gives a 50% increase in energy available. Just make sure you do not exceed the voltage ratings of the capacitors. Andrew Link to post Share on other sites More sharing options...
stewartingram Posted October 6, 2016 Share Posted October 6, 2016 Wrong way round. Parallel wiring gives the highest voltage at each coil. Andrew Agreed - my typo! Original now changed. Stewart Link to post Share on other sites More sharing options...
Theakerr Posted October 6, 2016 Share Posted October 6, 2016 Parallel. Run up to 6 points in one activation using a CDU powered by 25V 2A transformer. Motors are a mixture of Peco and Seep. Use multi strand tel wire to points since it is a pulse operation. Have done for about 15 years. No problems. Link to post Share on other sites More sharing options...
cliff park Posted October 6, 2016 Share Posted October 6, 2016 This whole conversation seems slightly eccentric. If I said to you that I had four lights in my lounge and I was thinking of wiring them in series you would think I was mad. I appreciate that solenoids are pulsed, but apart from that there is no difference. Link to post Share on other sites More sharing options...
Suzie Posted October 6, 2016 Share Posted October 6, 2016 If using the lighting analogy, think about wiring camera flash bulbs in series - lower level of illumination, but a compensating longer exposure time. Link to post Share on other sites More sharing options...
Free At Last Posted October 6, 2016 Share Posted October 6, 2016 I rewired the two fireglow bulbs in my gas fire and two external lights on my garage in series over 20 years ago and have never had to replace a bulb since. Link to post Share on other sites More sharing options...
DCB Posted October 7, 2016 Share Posted October 7, 2016 Tried this on Saturday with Triang lever switches, doesn't work. I know about the redundant pulse at the beginning of lever stroke (A and E positions on the real railway). Next step is to try a bigger CDU. The Triang switch is not compatible with CDUs, from memory it gives a pulse in the wrong direction first which discharges the CDU an then a weak pulse in the correct direction. A SPDT selector switch with a separate push button to energise works well. Watch out for over charged Capacitors, I had one explode. It was a 12 volt Lucas and it was on a 12 volt system. I use 36 volt Caps to give some headroom on 16 to 24 volts. Link to post Share on other sites More sharing options...
RMweb Premium melmerby Posted October 7, 2016 RMweb Premium Share Posted October 7, 2016 The Triang switch is not compatible with CDUs, from memory it gives a pulse in the wrong direction first which discharges the CDU an then a weak pulse in the correct direction. A SPDT selector switch with a separate push button to energise works well. Watch out for over charged Capacitors, I had one explode. It was a 12 volt Lucas and it was on a 12 volt system. I use 36 volt Caps to give some headroom on 16 to 24 volts. Why not just use a spring loaded centre off switch? http://www.maplin.co.uk/p/10a-toggle-switch-dpdt-momentary-on-off-on-n41kr Keith Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.