Points moters for 009 guage points

Page 1 of 2  

I'm very shortly about to order a significant amount of 009 track and points - all PECO, I know that you can do better if you build your own but I simply don’t have the time.

One thing concerns me, I currently use SEEP point motors for my 00 gauge track, all well and good and I’ve had no problems. However the "auxiliary switch" so to speak is nothing more than a slider between two contacts on the PCB and I’m concerned that if used with 009 gauge track there won’t be enough throw on the points for the auxiliary to work as designed.

Anyone here running 009 and can advise?

--
All the best,

Chris Wilson
  Click to see the full signature.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

"Chris Wilson" wrote

I don't think you'll have a problem Chris, but if you do you can always add a small microswitch. You're aware, I assume, that the 009 points are 'Insulfrog' and that there's no need for a switch to change the frog polarity.

John.

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

John Turner said the following on 15/11/2006 23:55:

And it's this 'Insulfrog' that seems to be the cause of so much poor running of many OO9 layouts I've seen. Short wheelbase, big dead section, not good!

--
Paul Boyd
http://www.paul-boyd.co.uk /
  Click to see the full signature.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

John Turner wrote:

Not in recent years - Peco 009 points have been electrofrog for a looooong time now, in fact the old insulfrog ones are very difficult to find any more. I can't comment on the effect of the limited throw on the auxiliary except to say that it's probably equivalent to N-gauge points, which will have the same throw. Personally I use an arrangement of two capacitors and one side of a DPDT switch which can operate a twin solenoid without the need for passing contacts, and that gives me the other side of the switch spare for switching the frog.

Dave Rogers

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I wondered as soon as I'd posted my message and when I came to check today found I was wrong. Thanks for correcting me! :-)

John.

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

John Turner wrote:

Not in recent years - Peco 009 points have been electrofrog for a looooong time now, in fact the old insulfrog ones are very difficult to find any more. I can't comment on the effect of the limited throw on the auxiliary except to say that it's probably equivalent to N-gauge points, which will have the same throw. Personally I use an arrangement of two capacitors and one side of a DPDT switch which can operate a twin solenoid without the need for passing contacts, and that gives me the other side of the switch spare for switching the frog.

Dave Rogers

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

...

I had to think about that but now I've figured it out in my head that's a very good idea. What size/type capacitors do you use? I don't have any at all at the mo to have a play with.

--
All the best,

Chris Wilson
  Click to see the full signature.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Chris Wilson wrote:

I got a batch of 2200 microfarad electrolytics a while ago from Radio Spares. One or two across the supply, then one for each point between the switch centre contact and the negative power terminal. One solenoid connects between the positive power terminal and one of the switch contacts, and the other between the negative power terminal and the other switch contact. There's never a DC circuit so there's no risk of heating the solenoids; when it's switched one way it charges the smoothing capacitor(s), the other way it charges the capacitor on the point, and the only current flowing is the transient on switching as the relevant capacitor discharges, so no need for a CDU. The drawback is that you need a capacitor for every point motor (although you can drive eg a crossover with a single capacitor) so it costs a bit.

The scheme wasn't my idea - I got it from a fellow Ipswich club member, Bob Wilkinson, who's used it on several other layouts - but I wouldn't use any other arrangement now.

On a related point, my daughter told me about a friend of hers who's making a railgun using capacitors from the flash units from used disposable cameras - apparently camera shops are happy to give them away. Anybody know what sort of size capacitors they use?

Dave Rogers

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hi Dave,

> The scheme wasn't my idea - I got it from a fellow > Ipswich club member, Bob Wilkinson, who's used > it on several other layouts

The idea has been around a long time -- I remember seeing it in mags in the fifties. Here's a diagram:

http://www.85a.ision.co.uk/info/solenoid_motor.htm

Martin. ------------------------------- http://www.templot.com

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ah the wonders of youth, thatmust bewhy I've never seen it before.

Many thanks

--
All the best,

Chris Wilson
  Click to see the full signature.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

wrote:

That's because what you describe *is* a CDU.

MBQ

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

snipped-for-privacy@hotmail.com wrote:

Yes, I was being rather imprecise there. What I mean is that there's no need for the constant current charging circuit that would be included in a commercial CDU for electric pencil switching - an advantage for me, as my electronics skills aren't up to much more than putting a few capacitors and switches in the right place. The big advantage, as the web page Martin gave says, is that the switch indicates the point direction, so it works really well on a track diagram style control panel.

Dave Rogers

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

snipped-for-privacy@yahoo.com said the following on 17/11/2006 09:52:

Far be it for me to criticise a ciruit that has apparently been around and in use since the 1950s, but the circuit Martin linked to only discharges through one of the coils, and even then only if it has had a chance to charge in the first place (hence the need to switch in each direction on first power-up). The other coil will never have the capacitor discharge through it - it can only be used to charge the cap. Therefore the only initial "oomph" it will get is from what the power supply can give it, rather than the capacitor.

--
Paul Boyd
http://www.paul-boyd.co.uk /
  Click to see the full signature.
Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

On Fri, 17 Nov 2006 10:13:33 +0000, Paul Boyd

Ah, good - someone else has raised what's been bugging me since I looked at the circuit. :-)

Jim.

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Paul Boyd wrote:

That's why I put a pair of 2200 microfarad smoothing capacitors across the supply - the other coil gets its impulse from the smoothing capacitors discharging into the point capacitor. In fact, the circuit I use is slightly different in that the capacitor and switch are the other way round - the centre switch contact goes to the high voltage rail and the two outer contacts go to the two solenoids. This means that there are four wires per point motor rather than three, because there can't be a common return; not much of an issue if you haven't got too many turnouts, but on a big layout it'll be significant. I'm not entirely sure the circuit in the diagram is right, but the version I use works very well.

The cautionary note about the capacitors retaining their charge is worth noting. After switching the power off I can switch a point back and forth typically 10-12 times on one of my layouts, and waiting a few hours doesn't make much difference. Only having a single 2200 microfarad capacitor across the supply seems to make it more like 3-4 times. Worth knowing if you're testing the circuit or altering the wiring - those big capacitors can give quite a spark.

Dave Rogers

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hi Paul,

> Far be it for me to criticise a ciruit that has > apparently been around and in use since > the 1950s,

Why not you? <g> Nothing's perfect, criticise away. But it's almost certainly older than that, the date I gave was the first time I saw it. In those days the capacitors were massive, but you could apparently buy them in your local ironmongers!

> The other coil will never have the capacitor discharge > through it - it can only be used to charge the cap. > Therefore the only initial "oomph" it will get is from > what the power supply can give it, rather than the > capacitor.

That's true, and why I didn't describe it as a "CDU", although I see someone else tried to. This design needs an adequate power supply. It doesn't make up for a feeble one.

In fact a power supply which is only barely adequate without this circuit probably won't work with it -- you need a decent sized transformer. I covered this point in the discussion on the 7mm Yahoo group (the reason I originally prepared the diagram).

The main advantages of this circuit are:

a) you can use any simple 2-way switch: toggle, slide, rotary, home-made, whatever -- it doesn't require a momentary contact.

b) that means that you can also use it with relays and logic to control the points.

c) most such switches usefully indicate the points direction on the panel diagram. Especially if you use a rotary switch with a pointer knob (but make sure it is a break-before-make pattern).

d) it is impossible to burn out the point motor coils. (Unless the capacitor fails -- make sure the capacitor voltage rating is at least 25 volts for rectified 16vac supply.)

But a CDU it ain't. Or at least, only in one direction. If the points are stiffer one way than the other, it's worth arranging that to be the discharge direction.

p.s. The circuit actually described by Dave requires a 4-terminal point motor (i.e. independent coils). The circuit at: http://www.85a.ision.co.uk/info/solenoid_motor.htm works the same way, but allows for 3-terminal point motors with a common coil connection.

Martin. ------------------ http://www.templot.com

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There's a circuit on the Modratec website (modratec.com/mud/php) that uses diodes as well as a capacitor so that you only need one wire plus the return wire to each point motor, instead of two. However, as far as I can see it is still only a "half CDU" in the same way as Martin's and Dave's.

Has anyone come across a simple circuit that can operate both coils by capacitor discharge using a toggle switch? I have an idea that with diodes this should be possible -presumably you would need two capacitors per point and a DPDT switch not an SPDT - but the details are beyond me unfortunately.

I'm interested in this as I have a bank of old Post Office keys that I want to use as a lever frame but using capacitor discharge if possible.

Thanks.

--

Regards

John



Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hi John,

> Has anyone come across a simple circuit that can operate > both coils by capacitor discharge using a toggle switch? > I have an idea that with diodes this should be possible

I would advise against mixing diodes with capacitor discharge. For reliability you would need some robust high-current diodes which will cost more than any saving in connecting wire.

Why bother with capacitor discharge units? All you need is to do as Dave has done and beef up the power supply with some capacitors across the output. This works fine for all methods of working impulse solenoids -- passing contact switches, centre-biased toggle switches, electric pencil + studs, etc.

If you add an additional capacitor per points-motor as in the circuit we have been discussing, you don't even need a momentary contact -- ordinary 2-way switches work too, such as your PO keys.

It works. It's simple. No diodes to fry. Why would you want more?

regards,

Martin. ----------- http://www.templot.com

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Martin -

That's very helpful - thanks.

I have no particular desire to make things more complicated than I need to; in fact, quite the reverse. I suppose I have become used to CD point operation over the years and for sure the three circuits I have seen - yours, Dave's (if I have visualised it right) and the Modratec one - all feature CD for one of the coils but not the other. As a result I had wondered if it was possible to use CD for both coils, but I think I see what you mean when you say that beefing up the power supply does away with the need for this.

So if I can follow this train of thought a little further, bearing in mind that words are no substitute for a diagram, I assume that your circuit also could have a capacitor added in parallel with the power supply to give the same effect as on Dave's? If so I think the Modratec circuit could as well. One advantage of the Modratec circuit is that only two wires - one feed and one return - need to be run from the switch to the point motor, thus cutting down on the inter-baseboard connections. However, it does need diodes to achieve this.

So, I think my choice will be between the Modratec circuit with added capacitor (two wires, with diodes) and your circuit with added capacitor (three wires, no diodes).

Any further thoughts would be most welcome.

Thanks.

--

Regards

John



Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Hi John,

> I assume that your circuit also could have a capacitor > added in parallel with the power supply to give the > same effect as on Dave's?

Yes, sure. Whether you really need it depends on the size of the power supply. I would use a 100VA transformer and a 10A bridge rectifier, which is more than adequate by itself to throw any ordinary points-motor. If you have a smaller supply you can beef it up by adding one or more capacitors in parallel with the rectified output. They should ideally be rated at least 35volts and designed for high-ripple currents, but it depends how rugged a system you want to build. Make sure the supply's bridge rectifier is good for at least 50volts PIV, preferably 100volts.

> One advantage of the Modratec circuit is that only two wires - > one feed and one return - need to be run from the switch to > the point motor

The circuit at:

http://www.85a.ision.co.uk/info/solenoid_motor.htm

also requires only two wires per points-motor. The third connection is to the layout ground (common return) which already exists on each baseboard. If you prefer a separate return for the points-motors, that is still only one additional wire per baseboard. There's no real need, providing the existing return is done with good thick wire, as it should be.

regards,

Martin. ------------- http://www.templot.com

Add pictures here
βœ–
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.