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

John Russo

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I've used these instead of the 17100s. Bullet Proof.

$2.50 a piece.


and


They are manufacture by PIC in Germany.

 

John Russo

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It fits nicely in the track and you can secure it with a small screw. They are completed sealed.

I used them connected to a Massoth 280R with the LGB MTS III central station.

FWIW, I wasted a year with a faulty LGB 55070 (Which the 280R replaces very nicely)

I was getting missed reads and was trying all kinds of magnets. When I put the new 280R in, I get 100% reads with any kind of magnet. I typically use the Massoth Loco Magnet 8420102
 

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Vincent
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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
Hi Alan,

Thanks for the tip, especially the idea of treating a reed switch as a consumable seems like a smart way to go. That way I'll always have a replacement in case one is acting up and, more importantly, why risk damaging a loco or rolling stock by keeping a questionable switch around. I also like Korm's suggestion of using duplicate switches for critical operations.

Cheers,
Vince
 

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Vincent
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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)
Hi Korm,

Thank you for the detailed list, this is very helpful! I don't think I am to the level of building my own reed switches yet, but perhaps someday! Either way, using the diode externally does open up many other commercial options as per the post by John Russo although I don't know what the what's-it-thingy does that you're speaking of (if you open up a 17100 there is a flat circular component which I assume is meant here) and if that is present in the other commercial options.

Cheers,
Vince
 

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Vincent
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I've used these instead of the 17100s. Bullet Proof.

$2.50 a piece.


and


They are manufacture by PIC in Germany.


Hi John,

These look really promising and are quite reasonably priced! Now, since I'm running in analog, I would need to use a diode to select for whether I want the + or - side of the AC to my EPL drive, correct? The direction of the diode determines which of the signals makes it through. Can you explain the difference in the AT ratings of the switches you linked? If I understand correctly, the AT rating can be used as a stand-in for distance between magnet and switch. As such, the higher the value, the more sensitive/responsive the switch should be? Why would you pick one value over another? For anyone else interested in learning more about reed switches, I did come across this explanatory pdf that was helpful.

I also found this cylindrical track contact from Shourt Line which has a rating for 2.5A! They have a few different variations, such as one with no terminal that may be of interest to people. The cost is the same as an LGB track contact, but seems to focus on quality components. If I understand it correctly, 2.5A would mean you could run 2 EPL motors from a single switch which you aren't supposed to do with the LGB ones.

It looks like PIC and many others on Digikey offer the cylindrical option as well although I didn't look too hard to find something that matched the 2+A for the Shourt Line track contact.

Thanks for all the great tips!
Vince
 

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Vincent
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One last message as a general response to people. It looks like at least one of my issues was a sluggish point/switch/turnout. It is not the only miss I experienced, but it does seem to not switch reliably. I haven't been able to determine the best way to tell if the issue is friction in the switch/turnout that the EPL drive can't overcome or something that is an issue in the drive itself. I was able to determine that it was not a misalignment of cog in the EPL motor itself. Are there any resources on doing maintenance on a switch and EPL drive, like what parts to lubricate? What to inspect and what issue for? How to test what may be causing the issue?
 

John Russo

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Hi John,

These look really promising and are quite reasonably priced! Now, since I'm running in analog, I would need to use a diode to select for whether I want the + or - side of the AC to my EPL drive, correct? The direction of the diode determines which of the signals makes it through. Can you explain the difference in the AT ratings of the switches you linked? If I understand correctly, the AT rating can be used as a stand-in for distance between magnet and switch. As such, the higher the value, the more sensitive/responsive the switch should be? Why would you pick one value over another? For anyone else interested in learning more about reed switches, I did come across this explanatory pdf that was helpful.

I also found this cylindrical track contact from Shourt Line which has a rating for 2.5A! They have a few different variations, such as one with no terminal that may be of interest to people. The cost is the same as an LGB track contact, but seems to focus on quality components. If I understand it correctly, 2.5A would mean you could run 2 EPL motors from a single switch which you aren't supposed to do with the LGB ones.

It looks like PIC and many others on Digikey offer the cylindrical option as well although I didn't look too hard to find something that matched the 2+A for the Shourt Line track contact.

Thanks for all the great tips!
Vince


Vince,

I have only used these in DCC and hence I do not worry about the polarity or amperage. As far as the AT rating, I would reach out to PIC. I recall getting a direct email response from one of their engineers. Keep in mind they sell commercially and so responding to a bloke fiddling with trains is not there mainstay.

PIC contact link: Contact

They can help sift through their options: Flatpack


Reed Simuator: Interactive Reed Switch
 

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Vincent
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remove the switch motor, check the friction moving the switch manually.
Thanks - I have manually moved the switch back and forth (with the motor attached) but it was hard to get a sense for the friction and if it was limiting movement. I will try without the motor. Is there a reason not to lubricate the metal bands the switch ends move across? The ones visible from above. Is there anywhere else in a switch that would or should be lubricated? And if it's in the motor? Do you lubricate or do anything inside there?
 

John Russo

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The switch motor has a rack and pinion setup inside and you could throw a little grease in there if needed.
 

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Vincent
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The switch motor has a rack and pinion setup inside and you could throw a little grease in there if needed.
Thanks John - I'll take a look at doing that. I will also reach out to PIC, perhaps after a little more research so I don't look like a complete incompetent.
 

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Vincent
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Looks like I just needed to do some more digging around to answer my questions:

Here is nice pdf explaining how reed switches interact with magnets and how magnet position can affect how and when a reed switch is activated. The presentation is also available as a youtube video from Standex Meder.

On the the AT measurement, AT stands for Ampere-Turns and I had the value wrong in my previous post. Lower AT means higher sensitivity and further distance between magnet and reed switch to activate. I presume a higher sensitivity also means a higher liklihood of false positives (i.e. creating contact when not desired like by a loco motor without a magnet), or slower recovery from being activated. John linked a reed switch with both 10-15 AT and one with 20-25 AT so presumably that's data that says both function fine for our purposes.
 

John Russo

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Just to muck things up a little more, I had a electronics guy look down on me because I was using reeds. He touted Hall Effect sensors as the better way to go. They do the same thing but they are solid state. He is probably right but in the model train world it seems we are all still using reeds and they are fine for our purposes.


Hall Effect vs Reed: Reed Switches and Hall Effect Sensors

and this piece about Reeds and magnets. https://www.kjmagnetics.com/pdfs/AN104.pdf
 

Greg Elmassian

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Hall effect sensors definitely need electronics added to make a "switch", as opposed to reeds which are indeed capable of passing a decent amount of current by themselves.

More electronics, more cost. Hall effect might be more reliable in the end.

Greg
 
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John Russo

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As I thought about this thread more and more I recall that the current draw on an EPL switch is relatively minor.

I don't think it gets anywhere near one amp.

Additionally the usual pulse is about a third of a second.
 

Greg Elmassian

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The steady state draw is low... the momentary surge is high, and that is what can burn reed switch contacts.

We have all experienced the momentary dimming of lights when a large motor or appliance starts....

If you don't believe there is a very high, but very short duration spark/voltage, here's the explanation

This is what causes pitting of contacts...

Greg
 
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korm kormsen

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... Either way, using the diode externally does open up many other commercial options as per the post by John Russo although I don't know what the what's-it-thingy does that you're speaking of (if you open up a 17100 there is a flat circular component which I assume is meant here) and if that is present in the other commercial options.

yes, that round thing, with two legs is what i meant.
many years ago in one of the forums somebody explained to me, how they are named and what they are for.
the name is long forgotten, but the reason for these what's-it thingies seems to be to protect the reed from burning closed too quickly. if you got a LGB reed contact open, you can see, that it is soldered in paralell with the reed.

when i read here about magnets, i remembered, that in the LGB manual ( http://kormsen.info/lgb-manual.pdf ) is mentioned, to look out, how to glue or clip magnets under the motor blocks from locos. they stress the point, that the magnet shall not be atracted by the magnet(s) of the motor. they shall be turned around, so that they want to push apart. (seems to have to do something with the force of atraction, the magnet has upon the reeds)
 

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Vincent
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yes, that round thing, with two legs is what i meant.
many years ago in one of the forums somebody explained to me, how they are named and what they are for.
the name is long forgotten, but the reason for these what's-it thingies seems to be to protect the reed from burning closed too quickly. if you got a LGB reed contact open, you can see, that it is soldered in paralell with the reed.

when i read here about magnets, i remembered, that in the LGB manual ( http://kormsen.info/lgb-manual.pdf ) is mentioned, to look out, how to glue or clip magnets under the motor blocks from locos. they stress the point, that the magnet shall not be atracted by the magnet(s) of the motor. they shall be turned around, so that they want to push apart. (seems to have to do something with the force of atraction, the magnet has upon the reeds)

Hi Korm,

Funny you should mention that! I had just found this site with the following schematic for the LGB Track Contact identifying the component as a varistor:

tips%20LGB17100.gif

I still don't really understand how the varistor works but your description is a helpful start. I'd be curious if John installs something along these lines with his PIC reed switches? Since they are so cheap I bought a few of the PIC reed switches to play with but I'd like to know if I'm bound to damage them or an EPL motor or have higher wear on the those components if I'm using them in analog without the Varistor.

So, interesting story about the loco magnet, I had bought a new one for my starter set Stainz and the instructions no longer include the guidance from the manual that you quote - which I remembered reading but only after I had already placed the magnet without checking for the alignment. Oh well...

Cheers,
Vince