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Electrical Control of Solenoid Turnout Motors

 
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ctgardner



Joined: 14 Feb 2008
Posts: 2
Location: Alton, Hampshire, UK

PostPosted: Fri Feb 15, 2008 2:56 am    Post subject: Electrical Control of Solenoid Turnout Motors Reply with quote

I have been looking at the various diagrams for controlling dual solenoid turnout motors (e.g. the Peco type) from the SPST switches provided with a MODRATEC lever frame. It occurs to me there is a solution which needs no electronics. This is to route the current to the two solenoids via an accessory switch connected to the turnout motor. i.e. if the turnout is set to the l.h. road, the current would be routed to the r.h solenoid.

Peco make two types of accessory switch. PL15 is of more rugged construction, and I guess the only question is whether the contacts are up to carrying the current supplied by a CDU. I would use the second set of contacts to switch current to the turnout crossing.

I wonder if anyone has a view on this approach? - if not, I'm certainly going to try it. It has the simplicity of being mechanically linked to the turnout position, which appeals to me.
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modadmin
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Joined: 15 Jan 2004
Posts: 288
Location: Australia

PostPosted: Fri Feb 15, 2008 6:39 am    Post subject: Reply with quote

Chris,

Three questions immediately come to mind:

1. How do you prevent the points from oscillating between the two states until the CDU pulse has decayed sufficiently?

2. How do you allow the CDU to recover its charge, since it will always be connected to at least one solenoid?

3. How do you generate a pulse for each lever position?

And for those who may be unfamiliar, our suggested methods are shown here:
http://MODRATEC.com/mud_points.php

... and a CDU is a Capacitor Discharge Unit. Such units store sufficient energy in a capacitor to operate a solenoid reliably but not enough to burn one out. They cannot supply a high continuous current. Once disconnected from the solenoid the capacitor charge rebuilds ready for a subsequent operation.
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ctgardner



Joined: 14 Feb 2008
Posts: 2
Location: Alton, Hampshire, UK

PostPosted: Fri Feb 15, 2008 8:38 am    Post subject: Reply with quote

I must have misunderstood the function of the switches - I thought they were momentary "on" as the lever passes over them (i.e. passing contact) - but from what you say they are either "on" or "off". Hence I understand the need for the electronics!
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