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CDU
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 Posted: Sun Nov 20th, 2016 12:37 am
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2foot6
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Hi,have been using peco point motors with AC and a probe,it works well but I have been considering a CDU to prevent coil burn outs.Does anyone have recommendations ,or what do you use? ......Peter



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 Posted: Sun Nov 20th, 2016 03:30 am
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Si.
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Hi Peter.

I used PECO point-motors some years ago.
I operated them with a stud-panel & probe, like you seem to have.
I was powering them with 12 Volt A.C.

I did actually make a 'capacitor discharge unit' for the setup.
My feeling though, was that the rapid discharge of the capacitor...
...was really quite VIOLENT on the mechanism & blades generally !!

With the possibility of coil burn out, quite minimal IMO...
...I scrapped the capacitor discharge unit & went back to 12 Volt A.C.

A side issue is, stud or electrical-switch damage, due to massive D.C. surge.
Something that is not so much the case when using A.C.

You might be better off sticking to what you have in my opinion.
Reducing the operating Voltage of course, is another possible option.

:moose:

Si.



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 Posted: Sun Nov 20th, 2016 02:18 pm
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Helmut
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CDUs are sometimes THE solution for balky twin-coil switch machines, especially those made by Märklin. Never have seen any mechanical damage caused by this sort of actuating them, but a lot of burnt coils and meltdowns due to insufficient force ( = current! ) - mainly with AC.
If following proven principles, they give reliable, trouble-free operation. One can even adopt that to DIY motor-driven devices, in brief you charge and discharge the capacitor via the motor. I have seen on a British website that they just linked the throwbar to a cheap DC-motor's shaft and operated it as a stall-motor. You bet that if no pushbuttons are used, you'll burn out the motor sooner or later. But using a capacitor will allow for a SPDT switch as position indicator and risk-free operation.



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 Posted: Sun Nov 20th, 2016 03:47 pm
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Si.
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Hi Helmut :wave:

Those Marklin point motors, sound like some old H&Ms I used to have.

They certainly woke up the signalman, on my sleepy GWR branchline terminus. :y:

Rattled the poor ol' dudes dentures, every time a pannier tank arrived. :old dude:

My old H&Ms used to cause brownouts on the guy next doors arc-welder sometimes.
When I upgraded to the PECOs, his Saturday morning welding, became trouble free.
My Dad couldn't believe the drop in the electricity bill either. :f:

;)

I can't help thinking the designer at H&M, used to pen bank vault actuators. :shocked:

:moose:

Si.



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' Mysterious Moose Mountain ' - 1:35n2 - pt.II
http://www.freerails.com/view_topic.php?id=7318&forum_id=17&page=1

' M:R:W Motor Speedway !!! ' - 1:32 Slotcar Racing Layout
http://www.slotforum.com/forums/index.php?showtopic=59295&st=0&a
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 Posted: Sun Nov 20th, 2016 05:49 pm
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Helmut
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The SM3 is a typical candidate for CDUs - lots of amps for just a split-second. The PECOs weren't that different either. I remember that I had some problems with powering them properly - they required sooo much more amperage than my Fleischmann's. That's where I first came across CDUs.



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 Posted: Mon Nov 21st, 2016 09:27 pm
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2foot6
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Thanks guys for your comments.After a long think and Si's
comments I will leave things as they are,but reduce the voltage to 12 volts AC providing it operates three motors at the same time.....cheers Peter.



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 Posted: Mon Nov 21st, 2016 10:58 pm
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oztrainz
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Hi Peter,
having let he magic smoke out of a Peco side-mount Peco point motor as shown below, earlier this year with straight AC and being surprised by how hot these coils can get in how short a time, I'd suggest the Peco CDU. The culprit was a single strand of wire that bridges across the switch contacts. I forgot to put my high-power spec on when soldering the wires to the switch when testing without a CDU :doh:)



Now I fire my points with Jaycar push button switches for each path like https://www.jaycar.com.au/black-miniature-pushbutton-spst-momentary-action-125v-1a-rating/p/SP0711 in tandem with a larger push button switch like
The reason for the double switch approach is that one of the clubs I was with had some of the smaller switches fail from burned contacts over prolonged use with a CDU. The work around was to close the small switch first then dump the current through it by closing the higher-rated larger switch. This defeated the problem.

I hope that this makes some sense for you,



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 Posted: Thu Nov 24th, 2016 05:03 am
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2foot6
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Thanks John for the idea of two buttons to press,not a bad idea.Probably wouldn't suit me but will suit other members of our group.It doesn't take much to burn out the coils as I have found out in the past.I will be sticking with the probe and stud system but the CDU still sounds like the safe way to go............Peter



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 Posted: Thu Nov 24th, 2016 05:17 pm
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Si.
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" The culprit was a single strand of wire that bridges across the switch contacts.
I forgot to put my high-power spec on when soldering the wires "

Hi Peter :wave:

As John has said, the reason he trashed an A.C. operated Peco point-motor, is basically because it was wired up incorrectly.

- - - - - - -

" It doesn't take much to burn out the coils as I have found out in the past."

Peter, I would be interested to know HOW you came to burn a Peco point-motor, using the A.C. stud & probe method ?
I can't imagine for one moment that this could be an easy thing to do !
My guess is you were using cheap switches, right ?

The great thing about using A.C. with stud & probe operation, is that the coil can't possibly be energized for any significant amount of time, unless of course you purposely hold the probe on the stud for ages, which seems highly unlikely.

Even using A.C with push-button switches, providing of course they are correctly specified, is WAY less likely to burn out a coil compared to using high D.C. current, which inevitably acts like an arc-welder ! on the switch contacts.
Whether the D.C. is from a C.D.U. or from a regular P.S.U matters little.
The life-expectancy of ANY switch or stud & probe setup is far far greater using A.C, than with contact damaging D.C.

- - - - - - -

On the Jaycar switches.

I used exactly the same switch, in a DIY throttle, some years ago.
It was running really small N-scale motors in 0-6-0s on the flat, pulling 3 cars tops.
I burned out about 3 of the Jaycar push-button switches, before giving up & replacing them with something 'fit for purpose'.

I have specified & installed hundreds and hundreds of switches over the years, both professionally & for hobby use.
The Jaycar push-button switch, literally sticks in my mind, as being the worst switch I have ever used.

It isn't well designed or manufactured.
I've never seen them used in any 'decent' product.
Witnessing them in action for point-motor operation as well, they fail very very quickly.
Their main selling point is, they are cheap, real cheap !
That seller ^^^ is overcharging BTW.

I found a good use for my remaining stock of them, a few years back.
They helped fill up the giant hole in Essex, where London dumps all it's garbage !

:moose:

Si.

The only C.D.U I would ever consider, is one that is operated by an S.C.R individually installed with each turnout.
Complex though.
By the time you've paid for & done all that, or bought a proper expensive push-button switch, you could probably have afforded a slow-motion point motor.
&
That's the 'Catch-22' of it all & why 9 times out of 10, a cheap job with economy parts, leads to unreliability & ultimately failure of switches and/or coils.
Or
You could use A.C with stud & probe...
...and have CHEAP as well as RELIABLE.

I could recommend some push-button switches, if anyone is interested.
The problem is you'll never buy them, they are way way too expensive !



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' Mysterious Moose Mountain ' - 1:35n2 - pt.II
http://www.freerails.com/view_topic.php?id=7318&forum_id=17&page=1

' M:R:W Motor Speedway !!! ' - 1:32 Slotcar Racing Layout
http://www.slotforum.com/forums/index.php?showtopic=59295&st=0&a
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 Posted: Fri Nov 25th, 2016 12:05 am
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2foot6
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Hi Si, the motors I burnt out were years ago when I was using switches for changing the points,one of the switches arced and burnt the motor coils:bang:.One reason I went for the probe and stud system was cost,reliability,ease of installing and operation.It would be very hard to burn out motors as you pointed out and the system is almost fool proof.I will stay with the probe system using AC,but may later on, as finances allow, install a CDU...........cheers Peter.



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