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Polarity Switching


StuartN
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I have a DCC model layout, started some time ago before I knew better because I used SEEP point motors in order to switch the polarity of the frog. Big mistake because the cheap SEEP motors don't work properly.

I bought a number of Gaugemaster Autofrogs, but they are expensive if you need to buy loads.

Also most of the switches I bought are Double Pole Double Throw Momentary switches. So I thought as a last resort and then only in my shunting yard that I would simply use one half of the switch to switch the polarity, but this would mean physically holding the switch while the loco passes the point. And this might damage the point motor. Could I use the switch if and when the loco stalls on the frog?

As you might tell, I am trying to do this on the cheap

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Not a great pic, but very simple in operation.

 

A small block of wood to bring it up to the correct height and just three wires. I appreciate it is with a Peco motor, but from memory Seep had a similar actuator. I gave up with Seep motors for exactly the reasons you have said re very unreliable switching.

 

IMG_1042.jpg.fbe515497fc6f4e934ac87971e93e7c1.jpg

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The SEEP polarity switch is extremely crude, depending on a physical connection made by a spring. I have thought about micro switches but my dexterity has become a problem and I can't think of an easy way of connecting the seep. Cost has now become a real issue, and like HS2 have exceeded my budget, so £18 a component is too expensive. I am interested in the Bistable Latch but I don't understand Chris M's circuit.

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Effectively the latching relay has two coils, a bit like the solenoid, so it latches either way. Each push button (the red ones) does two things:- it operates the solenoid and operates the relay, one way or the other. The contacts of the relay then switch the current to the rails. (Although I believe there is an error in one of the c/o connections, the top set lever spring is connected wrong)

Edited by cliff park
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A list of components and the circuit is here if it is of help? Link to item My circuit has 3 x direction diodes and 2 x resistors to reduce voltage to the relay, but all these can be omitted if wished!

Or use the Gaugemaster ready built units GM500. 

Edited by Brian
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If you use a microswitch care needs to taken regarding the strength needed for it to work - The old Maplin (RIP) did some that were very lightly sprung and worked fine off the throw of solenoid. Bought some from Rapid and they stopped the point motors from working. Thought the Hattons solenoids with the built in crank would be brilliant with a microswitch but even with the Maplin switches they struggled; did not pursue  that as I decided to go with Colbalts instead.

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4 hours ago, gordon s said:

A small block of wood to bring it up to the correct height and just three wires. I appreciate it is with a Peco motor, but from memory Seep had a similar actuator.

 

 

They do indeed have a similar actuator.

I have set up microswitches on all my SEEP motors like in your photo.

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I did precisely that with Seeps before I decided to go with Tortoises.

Some even had two microswitches, one operating each way, for complex switching such things as double slips.

The switching worked flawlessly (unlike the Seeps themselves)

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I am now caught up in doing the switching in the cheapest way, so two thoughts.

1. Switch off the power to the point motors and use the DPDT switch to change polarity.

2. See if I can use one Autofrog to switch more than one point frog's polarity. I am not sure why this shouldn't work if only one train is using the point system. My thinking is that the train meets one frog and the autofrog changes polarity to this and the next point, and when it then meets the next point, the autofrog changes the polarity again if need be. What I don't understand if the switching is momentary, when the short circuit occurs, or it acts as a switch. Surely the latter otherwise there would be no power in the frog before hand.

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No, no misunderstanding re Frog switching, which where moving contact switching is used is the same for DC and DCC.  But the reference to using an Autofrog in the DC section immediately flagged a possible concern that these cannot be used on DC :)  

Edited by Brian
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11 hours ago, StuartN said:

I am now caught up in doing the switching in the cheapest way, so two thoughts.

1. Switch off the power to the point motors and use the DPDT switch to change polarity.

2. See if I can use one Autofrog to switch more than one point frog's polarity. I am not sure why this shouldn't work if only one train is using the point system. My thinking is that the train meets one frog and the autofrog changes polarity to this and the next point, and when it then meets the next point, the autofrog changes the polarity again if need be. What I don't understand if the switching is momentary, when the short circuit occurs, or it acts as a switch. Surely the latter otherwise there would be no power in the frog before hand.

 

I use Tam Valley hex frog juicers on some parts of the layout. They are lightening quick and I have been very pleased with them. I also wondered about doing what you suggest in your point 2 above to save a bit of money.  However the metal wheels on anything else in the train will also bridge the regular rails to frog rails at each frog along the whole length of a train so everything on a given route needs to be correct at the same time. So once you allow for that I found limited opportunities to take any short cuts.

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