Reliability of LGB Track Contacts 17100 or Reed Switches and Best Practice for Use and Installation

[fairflixt]

Hi all,

I have set up a small temporary (in basement on carpeted floor of kid's playroom) automated analog track with a station stop and two trains/signals as per a number of threads on the forum and the World of LGB document. Basically as a train enters the station it activates the signal on the other track which releases the train waiting there. When a train leaves the station, it crosses a couple LGB track contacts, one to switch the signal of the station it leave back to stop (so the train stops once it completes it's loop) and one that moves the point at the entrance to the station so that the train will return to the track it came from. When the train enters it's track in the station after completing the loop, it activates another reed switch to release the original train. So three reed switches per train for a total of six.

So here's the problem, on more than one occasion, the trains have not triggered one of the reed switches/track contacts and resulted in an accident or at least a small heart attack on my part!

I'm wondering about what the experience has been with these switches? It appears that many people have had good experiences with them operating pretty reliably for extended times. So that leads me to think I'm not following some best practice for the sensors. For example, the sensors are maybe the length of one short track apart (i.e. 30 cm) or less. Is that too close? One loco I bought used and came with a magnet installed, is there a possibility the magnet has aged or that a newer magnet would be more reliably at activating the track contact? I have at least one track contact on a curved piece of track, could that cause it to be missed? What about power supply? I'm using a 16VAC power supply with only 7VA of power, maybe that's just too little? I've also wired power from some track contacts to others (i.e. in series, what can I say, I'm lazy) instead of powering each contact from a central distribution point. But I am only using one reed switch per actiom as is suggested by LGB and has come up a few times on the forums.

Would appreciate any thoughts, experience, or input to be able to watch my trains without constantly worrying that the automation isn't going to do what it's supposed to do!

Cheers,
Vince

 

[Paul M]

It might just be the carpets movement

 

[dutchelm]

The voltage is very critical. Too little & it doesn't work, too much& the reeds weld. 18v seems about just right.

 

[PhilP]

Out in the garden, the reeds 'rot-out', as the wire-ends coming out of the glass envelope are steel.

This is an observation in a British climate..

PhilP

 

[fairflixt]

It might just be the carpets movement

Argh, I was afraid some one would say this! Maybe I can test it on some of our tile/concrete flooring. I'll have to think about that...

 

[fairflixt]

The voltage is very critical. Too little & it doesn't work, too much& the reeds weld. 18v seems about just right.

OK, I did buy a 2A 18VAC power supply as an upgrade thanks to input from other forum members. I'll try that and report back.

 

[fairflixt]

Out in the garden, the reeds 'rot-out', as the wire-ends coming out of the glass envelope are steel.

This is an observation in a British climate..

PhilP

Some of the contacts I bought were new but some were used. I will inspect the used ones and see if there's rust or corrosion. In my case, everything will be indoors, so at least somewhat climate controlled... Thanks for the tip!

 

[LVT]

Some of the contacts I bought were new but some were used. I will inspect the used ones and see if there's rust or corrosion. In my case, everything will be indoors, so at least somewhat climate controlled... Thanks for the tip!

My experience, long ago, is that they were rather erratic, particularly when confronted by various pieces of motive power. I did notice that some of the stock LGB locos would trigger the reed without having been equipped with a magnet. The magnetic field of some motors was strong enough to trigger them. Twin motored engines could double pulse the contact, disrupting operation of the sequenced system. Fine tuning with close attention to the relative distance between the solidly fixed magnet and solidly fixed contact can yield worthwhile improvement.

 

[fairflixt]

The voltage is very critical. Too little & it doesn't work, too much& the reeds weld. 18v seems about just right.

Argh, the power supply I bought seems to put out a steady 20VAC, not 18. Does anyone know if that would be a problem? I had a hell of a time finding anything AC/AC online for 18V and 2+ amps that's reasonably priced as it was.

 

[fairflixt]

My experience, long ago, is that they were rather erratic, particularly when confronted by various pieces of motive power. I did notice that some of the stock LGB locos would trigger the reed without having been equipped with a magnet. The magnetic field of some motors was strong enough to trigger them. Twin motored engines could double pulse the contact, disrupting operation of the sequenced system. Fine tuning with close attention to the relative distance between the solidly fixed magnet and solidly fixed contact can yield worthwhile improvement.

How did you fine tune that distance? The track contacts snap into place on the rail and the magnet on the loco is fixed at least the small single motor locos I'm using.

 

[Greg Elmassian]

Actually, it is not the voltage that welds/burns the reed switches, it is current... normally the higher the voltage given to a "dumb" device, the more current is drawn (dumb as in a motor, inductor, solenoid, incandescent light bulb, resistor, etc.)

Greg

 

[fairflixt]

Actually, it is not the voltage that welds/burns the reed switches, it is current... normally the higher the voltage given to a "dumb" device, the more current is drawn (dumb as in a motor, inductor, solenoid, incandescent light bulb, resistor, etc.)

Greg

Hi Greg,

Thanks for pointing this out. Is it correct think of the current to a dumb device as a V=IR relationship? I.e. if I incrase voltage by ~20% than I can expect a 20% increase in current? How can I use this to assess whether feeding the EPL switches and contacts 20VAC is too much for them to handle? Or can I think of it as using up the available working life more quickly?

Vince

Edit: fixed my math, going from 18 to 20 is not 20%...

 

[Greg Elmassian]

Yes, but with inductive loads, there is a much higher initial surge then the steady state is less... this is an oversimplification, but important to consider.

You have probably seen the lights dim momentarily in a house when a large motor starts. The connection and disconnection are actually where you see the "arcing" and thus pitting of contacts.

I don't know the rating of the LGB reeds, but normally you would use reeds on an electronic switch, or a low current relay...

I would defer to people who have used the reeds long term to throw a switch.... in my experience this is not a good thing.

Greg

 

[fairflixt]

Yes, but with inductive loads, there is a much higher initial surge then the steady state is less... this is an oversimplification, but important to consider.

You have probably seen the lights dim momentarily in a house when a large motor starts. The connection and disconnection are actually where you see the "arcing" and thus pitting of contacts.

I don't know the rating of the LGB reeds, but normally you would use reeds on an electronic switch, or a low current relay...

I would defer to people who have used the reeds long term to throw a switch.... in my experience this is not a good thing.

Greg

Hi Greg, thanks for clarifying. I will try to restrain my impatience until someone else responds. In the meantime, I did find something on Digikey so at least I'll have something more trustworthy going forward.

 

[Software Tools]

Argh, the power supply I bought seems to put out a steady 20VAC, not 18. Does anyone know if that would be a problem?

It should be fine, a few volts either way wont make a great deal of difference in your particular application of EPL tech.

 

[dutchelm]

OK, I did buy a 2A 18VAC power supply as an upgrade thanks to input from other forum members. I'll try that and report back.

I use one of the little transformers that LGB put in their train sets before they changed to SMPC. Seems to work OK.

 

[AlanL]

Assuming that you have a decent enough power supply, (the 20 vac should be good).
Reed switches are very lightweight as switches and the erratic operation is a sign that the contacts are failing.
Even though they may be rated at (say) 1 amp doesn't mean that they will switch 1 amp forever especially when operating LGB point motors.
If you are using LGB components (reeds and magnets) then you would assume that they are tuned to operate correctly without any fine tuning. Generic components could require fine tuning.

I would regard reed switches as consumables and suggest you replace the troublesome ones and keep plenty of spares.

I run my trains 'automatically' and can know the problems when a train misses a sensor.

Alan

 

[Greg Elmassian]

Again to reinforce, on certain loads (motors and solenoids are included), the PEAK current can be much higher than the RATED current, so without sophisticated instruments, trying to be sure your reed switch is not overtaxed could be impossible for most people.

they are best at switching very low current, like logic levels to decoders.

Greg

 

[korm kormsen]

hello,

carpet - i doubt, that this should be the reason. but you could put thin plastic or cardboard sheets between carpet and ties.
voltage - one of my oldest starter transformers is rated 18vDC and 15vAC. for the last forty years or so(since epl was introduced) it did work with reeds. additionally i use a 16vAC maerklin.
position of reeds - i never put them too near of starting and stopping points. (see Greg's explanation)
"erratic" behaviour - in my experience that is not the reed's fault. reeds either work, or burn out (and never work again). either you got bad cables/connections or bad magnets.
magnets - use strong ones. they need not be originals. i have used furniture door magnets and, lately, magnets out of old pc hard disks.
belts & suspenders - on various places, where a failing reed could make great damage, i had two reeds (wired in paralell) at a distance of two ties/sleepers.
price of reeds - for some of my layouts i needed lots of reeds. more than my purse liked. so i broke open one (burnt out), of the LGB reeds, took it to an electronics shop and bought some dozens of reeds, diodes and what's-it-thingies of the same size as the originals. together with wooden sleepers, to mount the things on, i made my own reeds. see steering (scroll down to last pic) (instead of two "outs" i use just one and put an "external" diode. oriented as needed.)
since then i never bought any reed switch again. the diodes are eternal, as are the what's-its. i only have to replace the reed propper. (it's a little bit bitchy to bend the feet of the reeds, without breaking the glas)

 

[PhilP]

Excellent! - I even raised a smile at Engine No. 9..

My tip for bending the wires on reed-switches :
Hold the wire, adjacent to the glass envelope, in thin nose pliers.. Then bend the wire on the outside of the pliers (you can usually push it over with your thumb.

PhilP