Adding Latching Relay to Seep Point Motor to Change Frog Polarity

[grob1234]

Hello,

 

Please forgive this post, I know it duplicates some aspects that have been posted before, however not being an electrical wizz, I need things in a simplified format.

 

I currently have an N Gauge layout (DC Operation), and Peco code 55 turnouts with electro-frogs. I use Seep PM1 point motors, which are used to change frog polarity. However, they are unreliable in terms of changing polarity, as the throw is not sufficient at all times to ensure changeover 100% of the time. Please note I DO NOT want to change the point motors, I simply wish to improve them.

 

Currently, they are wired as follows, in the standard manner. I use momentary (on)-off-(on) SPDT switches via a CDU. This will not change.

 

Having read @Brian website https://www.brian-lambert.co.uk/Electrical_Page_3.html, I understand the need for a Twin Coil 12v Latching relay, and he recommends https://www.bitsboxuk.com/index.php?main_page=product_info&cPath=253&products_id=1924 

 

To me this seems like any other electrical component, and as I need 12 of them, is this https://www.rapidonline.com/hongfa-hfd2-012-s-l2-d-pcb-signal-relay-12vdc-dpdt-2a-71-4712 the same thing, but at a better price? Or could someone recommend a cheaper equivalent product?

 

In terms of wiring in the latching relay, I don't understand the need for the diodes Mr Lambert shows? I don't intend to have LED's for route indication, and so my idea would be to wire it in as follows:

 

Would this work without the need for diodes? From the wiring diagram below, I'd be using terminals 1 and 10 to operate the latch, and 13, 11 and 9 for the frog.

I have taken the wiring for the relay from the datasheet thus: 

 

Any (simplified) help would be much appreciated. 

 

 

Edited March 23 by grob1234

[TheSignalEngineer]

Diodes for stopping backfeed through relay coils? If they are not there throwing the control switch will try to energise both sides of the Seep simultaneously depending on the internal arrangements in the relay.

[Jeremy Cumberland]

In your first diagram, where is the return wire going to the C terminal of the point motor? You appear to be under the impression that the black wire is a return, whereas it is a supply (at +12V when energised by the switch).

 

Here is a wiring diagram for a Seep SP1:

 

Essentially you need a latching relay with the same two-coil configuration, and you wire the coils of the latching relay in parallel with the coils of the point motor. The latching relay wiring diagram in your post is for a single coil device, and this won't do. Instead you need one like this:

 

Connect 1 on the latching relay to A (or B) on the point motor, connect 2 on the latching relay to B (or A) on the point motor, and connect 15 and 16 on the latching relay to C on the point motor. With a DC supply you shouldn't need diodes, but if Brian Lambert says to fit them I would.

 

You then switch the frog by connecting 13 (or 4) to the frog feed and 9 and 11 (or 6 and 8) to the track feeds.

 

The relay you linked to in your post is a two-coil latching relay, indicated by the L2 in the part number (012 is the coil voltage) and should be fine.

[grob1234]

3 hours ago, Jeremy Cumberland said:

In your first diagram, where is the return wire going to the C terminal of the point motor? You appear to be under the impression that the black wire is a return, whereas it is a supply (at +12V when energised by the switch).

 

Here is a wiring diagram for a Seep SP1:

 

Essentially you need a latching relay with the same two-coil configuration, and you wire the coils of the latching relay in parallel with the coils of the point motor. The latching relay wiring diagram in your post is for a single coil device, and this won't do. Instead you need one like this:

 

Connect 1 on the latching relay to A (or B) on the point motor, connect 2 on the latching relay to B (or A) on the point motor, and connect 15 and 16 on the latching relay to C on the point motor. With a DC supply you shouldn't need diodes, but if Brian Lambert says to fit them I would.

 

You then switch the frog by connecting 13 (or 4) to the frog feed and 9 and 11 (or 6 and 8) to the track feeds.

 

The relay you linked to in your post is a two-coil latching relay, indicated by the L2 in the part number (012 is the coil voltage) and should be fine.

Thank you very much Jeremy, that’s exactly what I needed to see. I wouldn’t have got the wiring like you have indicated for the relay without an awful lot of head scratching, but it makes sense now.

 

I forgot about port c from the seep pm1 in my original post, but it’s there on my layout and all tested and working fully… except the frogs… sometimes! It would make sense if C was my common return wire. It’s a while since I did it.  I think I’ll go with this, and might risk foregoing the diodes and keep it simple.

 

Once again thank you for your succinct reply.

Edited March 23 by grob1234

[kevinlms]

Just to point out something that may be not be obvious to you. Did you realise that suitable diodes are ultra cheap, so you are only talking about pennies potentially saved.

You could fit diodes everywhere, for less than the cost of a burnt out point motor or latching relay!

[RFS]

Gaugemaster have a ready-made relay switch designed for this purpose - see here.

 

Being DPDT one switch will handle the frogs of two points forming a crossover, for example. 

Edited March 23 by RFS

[melmerby]

When I had some Seeps I did the frog switching with 1 or 2 microswitches (depending on number of frogs)

I used the ones with the long actuating arm resting on the pin extension of the Seep.

100% reliable

[GrumpyPenguin]

Personally I would not power latching relays from a CDU, it would work but not, I suspect for long.

 

Having said that I really don't understand why modellers still use solenoid motors that require a CDU (crude/nasty things) to operate them anyway.

[Suzie]

Just to add a few notes:-

 

1. Hongfa relays are fine for this. I have some twin coil latching HFD3 relays (slightly smaller than the HFD2 types but adequate for the task). They will still switch 4A (see point 2) and carry quite a bit more current.
2. Use both sets of contacts in parallel to increase the amount of current that the frog switching contacts can handle. This will improve reliability over the long term especially if people are prone to run the point the wrong way and short on the frog.
3. Because of the extremely low resistance of the SEEP motors the voltage at the motor is often very low and may be insufficient to fire a 12V relay if mounted near the motor even when fed by a CDU. It is best to mount the relays near the control panel to ensure that sufficient voltage is available. I understand this can be inconvenient on a DC layout, so if you don't want the extra wiring you might need to select the voltage of the relay coils carefully to ensure reliable operation. I have seen installations where even when using a CDU giving out 24V  (the typical output of a CDU fed with 16V AC) there was less than 6V available at the point motor due to resistance in the switches and wiring. Some CDUs will run at up to 35V - it can sometimes be helpful to use a regulated 35V DC supply to get the most out of a CDU if your wiring is not the fattest cable. Consider using a cheap adjustable DC-DC convertor running from a 12V supply to give you a cheap source of 35V to the CDU that can be adjusted lower if required.
4. While the inverse parallel diodes across the coils are only essential when using semiconductors to switch the points - they will reduce arcing across the switches and extend their life. There will be far more back EMF (in terms of power) from the point motors than the relays so even if you don't have relays you should use inverse parallel diodes (no one will tell you this!).
5. You say that you don't want to change your motors in which case you will have to live with the shortcomings of what you have - but in future consider using the solenoid motors with higher resistance coils (Peco PL10E or PL10EL for example) because the lower currents involved result in much higher voltage being available near the points for powering latching relays and you don't need to worry so much about super-fat wiring to the solenoid coils, CDU and switches.

Using latching relays is super-reliable if you can implement them correctly. I got my good results by beefing up the wiring (especially from the CDU to the control panel), upping the CDU output voltage to 35V, and mounting 24V latching relays near to the control panel. The Hongfa relays will typically fire at about 75% of the rated voltage and will take 150% of the rated voltage so you do have a nice big window to play with (for example a 24V relay will fire at 18V and will be OK at 36V so will not be damaged if a solenoid goes open-circuit and will take a bit of loss in the wiring).

 

I have probably raised more questions than I have answered but what you are trying to do is not as simple electronically as it first appears.

[grob1234]

Thank you all for the informative replies. The answers I have received show that this isn’t as straightforward as is sometimes suggested, but is a reliable way (if implemented correctly) of improving the reliability of this type of point motor. It is also highlighting things I have not come across in my previous research, so I’m very appreciative of this.

 

i had noticed the gauge master version - I suppose I’m trying to keep costs down, so the DIY route and a bit of easy soldering is attractive.

 

With regards to diodes, I might as well order a few at the same time and see how I get on incorporating them into the wiring. Although as Suzie mentions, it seems they “should” be present in the normal point motor wiring anyway!

 

Thank you for your points (excuse the pun) Suzie. I’ll use both sets of contacts on the relay as you suggest, it is not something I thought about but makes sense. I will also check the voltage output. The layout is small, and the wiring runs are not long, and I have 2 dedicated CDUs so I hope the voltage will be sufficient to fire a 12v relay, I’m assuming I’ll need about 9v based on what you’re saying.

 

Although I didn’t intend this to be a thread discussing the merits of solenoid point motors, the reason why they are used is obvious. They are readily available, they are cheap, relatively easy to install, reliable, and as pure point motors they work well. The switching element can be tricky, as I have found, hence the need to improve what I have. Additionally, people may not be aware of servo operated points, I certainly wasn’t at the time I made this layout, and higher cost options (cobalt, tortoise etc) may not always be viable. For the next N Gauge layout that I am currently planning, I will be using slow action point motors with built in switching. You live and learn, however, I still feel that solenoid motors definitely have a place.

 

I think I have enough to go on, I’ll order some relays and some other bits and see how I get on.  I’ll try and post some pictures and draw up some wiring and specs for anyone who’s interested in future. Many thanks, Tom.

[RFS]

A while ago now I did use a lot of Peco point motors and used some relays as you are thinking of. I now use Tortoise motors with their built-in switches and the relays have been reused to work colour-light signals. I used them mainly where I had two points forming a crossover as one relay was equivalent to two Peco switches.  Cost about £2.50 in components at the time - relay, a piece of board, diodes and terminals. The diodes were needed as they were being operated by Lenz LS150 decoders which were supplyin AC current. 

 

LS150 input at the top, two sets of switch terminals at the bottom. 

 

 

 

[grob1234]

7 minutes ago, RFS said:

A while ago now I did use a lot of Peco point motors and used some relays as you are thinking of. I now use Tortoise motors with their built-in switches and the relays have been reused to work colour-light signals. I used them mainly where I had two points forming a crossover as one relay was equivalent to two Peco switches.  Cost about £2.50 in components at the time - relay, a piece of board, diodes and terminals. The diodes were needed as they were being operated by Lenz LS150 decoders which were supplyin AC current. 

 

LS150 input at the top, two sets of switch terminals at the bottom. 

 

 

 

 Nice, neat little set up there. I doubt very much mine will look as refined!

[melmerby]

16 hours ago, melmerby said:

When I had some Seeps I did the frog switching with 1 or 2 microswitches (depending on number of frogs)

I used the ones with the long actuating arm resting on the pin extension of the Seep.

100% reliable

Like so

Cheap cheerful & reliable:

 

 

 

BTW Seep coils are about 2.8 ohms each.

Edited March 24 by melmerby
finger trouble

[grob1234]

I can see that would work well Keith. Nice and simple!

[kevinlms]

On 25/03/2024 at 00:31, melmerby said:

Like so

Cheap cheerful & reliable:

 

 

 

BTW Seep coils are about 2.8 ohms each.

How is the SEEP secured?

[melmerby]

On 25/03/2024 at 13:44, kevinlms said:

How is the SEEP secured?

Usually with screws, they were pulled out of my spares box to be photo'd on a piece of scrap wood.

You could use a hot glue gun.

Edited March 26 by melmerby

[grob1234]

Well, I said I'd report back.

 

Got my 12 Latching Relays from Rapid Online, and they certainly were Rapid. Ordered at 5pm, came the next day at 9am! Excellent!

 

Tested a 12v relay with a 9v battery. Heard the little click. Relay works, so far so good. Get the multi meter out test the output, and yes its working as advertised. Continuity switches between +ve and -ve. Remove the power and there's no continuity at all. Ok good that seems to make sense, if the relay isn't powered, the little electro magnet inside or whatever isn't making a circuit.

 

Wire one into the layout feeling happy that I may have found the solution. Gingerly apply power, and the point works flawlessly in the straight on configuration. Throw the point. Apply power. Nothing. Test the relay. No click. Remove and test again. Nothing. Test with multi meter. Circuit is permanently open one way and won't switch back. I'm assuming too much voltage has come through the relay and welded it to one side, either way, its buggered! 

 

Really not sure what to do about this. I have a CDU supplying the point motor, I chose 12v latching relays assuming the voltage would be low. Without spending another £24 on another set of 24v relays, it seems my dream of perfect point polarity switching on the cheap is over.

[kevinlms]

On 27/03/2024 at 05:32, melmerby said:

Usually with screws, they were pulled out of my spares box to be photo'd on a piece of scrap wood.

You could use a hot glue gun.

OK, but your photo doesn't appear to show screws for the motor, so glued?

The switches are on a chunk of timber, with 2 screws holding it secure and two further pairs of 2nd hand screws holding the switches to the block of wood.

[kevinlms]

On 24/03/2024 at 10:23, GrumpyPenguin said:

Personally I would not power latching relays from a CDU, it would work but not, I suspect for long.

 

Seems that you are 100% right!

[grob1234]

14 minutes ago, kevinlms said:

Seems that you are 100% right!

Well done that man!

 

12 11 Latching relays now available on Ebay...

Edited March 28 by grob1234

[RFS]

5 minutes ago, grob1234 said:

Well done that man!

 

12 11 Latching relays now available on Ebay...

Can you not wire the relay direct to the power source and only the point motor via the CDU?

 

What type of relay did you purchase, in particular what switching voltage? Mine are Hongfa HDF2 which are rated at 30V DC 3A for switching power. I use them with Lenz LS150s whose output is 16V AC at 3A, with diodes to convert the input to DC. Have been using them for years with no problem. Not now with points but with colour light signals. 

[grob1234]

10 minutes ago, RFS said:

Can you not wire the relay direct to the power source and only the point motor via the CDU?

 

What type of relay did you purchase, in particular what switching voltage? Mine are Hongfa HDF2 which are rated at 30V DC 3A for switching power. I use them with Lenz LS150s whose output is 16V AC at 3A, with diodes to convert the input to DC. Have been using them for years with no problem. Not now with points but with colour light signals. 

 

How do you mean? My limited understanding is that the power to move the solenoid comes from the switch via the CDU, and the solenoid requires the power of the CDU in order to move it. How would the relay be switched in this instance?

 

They are Hongfa 12v Relays, the power to the CDU is 16v AC and the output from the CDU is whatever it is, as I couldn't measure it as the power is too momentary. I'm guessing there are too many volts going through it, and I've blown the relay!

[Jeremy Cumberland]

1 hour ago, grob1234 said:

Remove the power and there's no continuity at all. Ok good that seems to make sense, if the relay isn't powered, the little electro magnet inside or whatever isn't making a circuit.

If you remove the power from a coil circuit (pins 1 and 16 or 2 and 15), the switches (pins 4, 6, 8, 9, 11 and 13) should remain set exactly how they were before.

 

Can you post a photograph of a relay, and an internal wiring diagram if you have one? What is the part number?

 

You will only burn out the relay coil if the CDU output voltage is too high. I would not expect any problems with a CDU powered by 16 V ac, and this is a very common arrangement. A more likely scenario for the relay not operating (assuming it is the correct type of relay) is that it isn't getting enough voltage because the SEEP is stealing all the current, as was mentioned earlier in this thread.

[grob1234]

22 minutes ago, Jeremy Cumberland said:

If you remove the power from a coil circuit (pins 1 and 16 or 2 and 15), the switches (pins 4, 6, 8, 9, 11 and 13) should remain set exactly how they were before.

 

Can you post a photograph of a relay, and an internal wiring diagram if you have one? What is the part number?

 

You will only burn out the relay coil if the CDU output voltage is too high. I would not expect any problems with a CDU powered by 16 V ac, and this is a very common arrangement. A more likely scenario for the relay not operating (assuming it is the correct type of relay) is that it isn't getting enough voltage because the SEEP is stealing all the current, as was mentioned earlier in this thread.

 

Its these ones Jeremy:

 

https://www.rapidonline.com/Catalogue/Search?Query=Hongfa HFD2%2F012-S-L2-D PCB Signal Relay 12VDC DPDT 2A&Size=20

 

What concerns me is that the relay switched 'on the bench' with a 9v battery, and now, the same relay won't switch under the same conditions with a 9v supply.

 

I'm just charging up a 12v power supply, to see if that works....

 

 

[RFS]

1 hour ago, grob1234 said:

They are Hongfa 12v Relays, the power to the CDU is 16v AC and the output from the CDU is whatever it is, as I couldn't measure it as the power is too momentary. I'm guessing there are too many volts going through it, and I've blown the relay!

 

Same relays as I have. Their input must be DC which is why I fitted diodes. Check the output of your CDU as I suspect its output might be AC.