Switch Cobalt point motor using Scalefour Lever frame (single pole microswitch)

[justin1985]

I've got a Scalefour Society Lever frame that I built for a project I'll no longer be using it for, which I'd like to use on a layout that I'd like to refurbish and operate with Cobalt point motors so I can have a single control panel for both boards (it currently has wire in tube with ancient Ratio plastic levers mounted in inconvenient locations). The Scalefour frame is designed for use with mechanical linkages and includes rails for mounting standard microswitches.

 

The Cobalt point motor (omega model, but presumably the same for any model, or Tortoise) is switched by reversing the polarity of its feed - using a cross wired DPDT switch. Is there any way of wiring the microswitch in the lever frame to trigger the point motors?

 

My first thought is to use the microswitch to trigger a miniature relay, which is DPDT. Is that a good idea? The obvious issue that comes to mind is that the relay would be "on" all the time the lever is "on" - and so presumably getting hot and using a fair amount of electricity? Does that make it a bad idea?

 

Would there be any other way of achieving the combination of lever frame and stall motor point machine? Should I just bite the bullet and use standard DPDT switches and forget about the lever frame? (or shell out for DCC Concepts own lever frame ...)

 

Justin

 

 

[cliff park]

You could do it with a positive and negative supply and the microswitch using the diagram below:-

 

 

[Grovenor]

You can use a relay like you suggest, relays are designed to be on for long periods and don't use much juice or get hot, install the relays close to the point machine so minimise the wiring. Note if the relays are on with the point lever pulled reverse then they should not be on for long periods anyway as points are mostly normal most of the time.

An alternative method is to use a split potential power supply that allows you to wire from an SPDT microswitch dirct to the points without needing relays. Its the preferred method IMHO and details are given in the Tortoise instructions. (And as per diagram above posted while I was typing, you create the +12 and -12 from an AC supply just using two diodes).

Regards

PS. Here's the link to the Tortoise instructions, look at diagrams 2 and 3. http://www.circuitron.com/index_files/ins/800-6000ins.pdf

It will work just the same with Cobalts.

[John ks]

I agree with the previous posts

 

The two diagrams give a comparison between a relay or split supply

 

With a relay you will need a relay for every point and more complex wiring

 

With the split supply you only need 2 diodes, if they are rated at 1 amp they will power up to 20 Cobalt's, possibly more. (if my 30second research at Cobalt's site is reliable)

 

 

Hope this helps

I am using some Cobalts & Tortoises ( I much prefer the tortoise) & the power supply is a split DC supply I.E. (+)12V, 0V ,(-)12V

 

John

 

 

 

[justin1985]

Thanks all, that's really helpful! The split AC supply with diodes looks like the way to go. I hadn't thought to look at the Tortoise instructions, which are much clearer.

 

I had been drawn to the Cobalt rather than Tortoise simply because of space. The few cm saved on depth especially allows them to fit under the existing layout as-is, whereas Tortoise would need the board to be extended downward. Are Tortoise that much better that it would be worth doing that?

 

Justin