12070 supplementary switch - max current

[Ralphmp]

Can anyone confirm what is the maximum continuous current that the later 12070 supplementary switch (the one with the micro switches) can safely handle when used on a DCC layout?

I've seen in another thread from days gone by that 12070s were limited to 3 Amps, but not sure if this limitation is still, wait for it, "current'. (sorry!)

I'm looking at a way of automatically turning the power to an isolating track section on / off using one of these 12070 supplementary switches, and although the biggest current draw I've noticed on my layout to date has been around 3 amps, it may well be higher so I don't want to overload the switch.

Thanks in advance

 

[Neil Robinson]

From memory the switch is rated at 30V 3A AC, 2A DC.
The switch's spring carries the current and loses its springiness if overheated.
I recommend that the LGB switch is used to switch the low current coil of a relay with the relay contacts taking the higher current.

Here's one example that'll handle 10 A, the coil is a nominal 900mW so, at 12V the current supplying it via the LGB microswitch is only 0.075A.

http://uk.rs-online.com/web/p/non-l...43D3832372D38323038267374613D3832373832303826

 

[stockers]

I used to use these switches to power loops and sidings with no problems at all. My main running loop was powered thus.

 

[stockers]

 

[James Day]

From memory the switch is rated at 30V 3A AC, 2A DC.
The switch's spring carries the current and loses its springiness if overheated.
I recommend that the LGB switch is used to switch the low current coil of a relay with the relay contacts taking the higher current.

Here's one example that'll handle 10 A, the coil is a nominal 900mW so, at 12V the current supplying it via the LGB microswitch is only 0.075A.

http://uk.rs-online.com/web/p/non-l...43D3832372D38323038267374613D3832373832303826

Thanks Neil,

You have opened my eyes there!

Never even thought about that before. I use loads of them on my DC layout and each section has a supply of up to 5amps! Luckily I have never had any trouble.

I still use the older 1203 type switches on signals and once had one fail in service due to the switch being wet and the current passing through it etched away the contact strip on the PCB!

James

 

[Ralphmp]

Thanks for the responses - some food for thought.

 

[Kayanbee]

Hi, I found the switches put too much strain on the LGB point motor and made it unreliable. I changed all my LGB supplementary switches for latching relays. 2 pole ones will fit in the existing housing or you can have 4 pole ones elsewhere. Neither need to be in the housing as they are not mechanically connected. I use them for switching the power to the appropriate track and also for an indicator LED on my control panel to show the direction set. I have never had a problem with current overload, I run analogue wit ha Hartz 2-10-2 with carriage lighting and had no problems.

 

[korm kormsen]

Hi, I found the switches put too much strain on the LGB point motor and made it unreliable.

same thought here, but different solution.
additional to the turnouts with their switchmotors i used other switchmotors with the add-on switch to change current. (activated by other reeds too)

 

[chris m01]

My points all switch with these attached and provide both track power and route indicator power. The actual track switching has never been a problem. Sometimes the switch is carrying up to 24volts at about 3 amps but only for 10 seconds or so. I have found these switches to be quite temperamental with a number of failures due to pcb solder failures. After a number of repairs they seem to have settled down this year. I did make a plan to replace them with latching diodes but as they are not giving me any grief at the moment that plan is on hold.

 

[Ralphmp]

same thought here, but different solution.
additional to the turnouts with their switchmotors i used other switchmotors with the add-on switch to change current. (activated by other reeds too)

Thanks Korm. Interestingly, this is what I've been contemplating doing. Basically, i have a long single track layout and I typically have 2 trains running at the same time. To avoid having to manage both trains all the time (i.e. I want to sit back, relax and watch them run round), I want a way of ensuring trains do not catch up with each other; something like

1. First train triggers a track contact,
2. this sends a signal to a switch decoder
3. The switch decoder operates a switch motor (which may or may not be attached to a set of points)
4. A 12070 attached to the switch motor cuts power to an isolating section of track behind first train, so any following train stops when it enters this section
5. Having travelled a suitable distance the first train triggers a second track contact
6. This contact sends a signal to the switch decoder
7. The decoder operates the switch motor with 12070 attached to restore power to the isolating section
8. The second train continues on its way at a safe distance behind the first.

My thinking is that this system will work with any loco that has a magnet fitted to it - no need for automatic drive programming on my Massoth central station.

Appreciate its a bit crude but having had a couple of exciting moments recently when I dozed off, I've decided I need some kind of fail safe system other than the "oh b***er, hit the emergency stop on the Navigator!!!" approach.

 

[Ralphmp]

Hi, I found the switches put too much strain on the LGB point motor and made it unreliable. I changed all my LGB supplementary switches for latching relays. 2 pole ones will fit in the existing housing or you can have 4 pole ones elsewhere. Neither need to be in the housing as they are not mechanically connected. I use them for switching the power to the appropriate track and also for an indicator LED on my control panel to show the direction set. I have never had a problem with current overload, I run analogue wit ha Hartz 2-10-2 with carriage lighting and had no problems.

So could a Massoth track contact be used to "open" and "close" these relays or would I need another type of reed switch (or similar)?

 

[ntpntpntp]

Have to say I never found any problem with 12070s straining the LGB point motor - they always worked fine. The point motors where operated by locally installed NCE SwitchKat DCC decoders.

I only used the 12070 switches for frog polarity, so current flow through the microswitch was only for the duration of the loco passing over the frog. No power flow whilst actually switching, so no arcing of the contacts. Beyond the frog the track power was controlled by section switches (as for a DC layout) though as I was running DCC 99% of the time, all sections were simply left on.

 

[korm kormsen]

...
My thinking is that this system will work with any loco that has a magnet fitted to it - no need for automatic drive programming on my Massoth central station....

that is, what i did on my last layout. two overlapping circles with various trains each, that triggered each other.
in the station, where the circles "met", i needed to reverse power. all simple DC.

at the moment (the last 9 or 10 years) i build a circle with six passing sidings and two dead-end stations for 8 trains (4 in each direction)
all components and partial systems tested, only the whole is progressing slowly.
all without Massoth stations or other high tec gimmicks.

 

[Tim Brien]

Hi, I found the switches put too much strain on the LGB point motor and made it unreliable............

When my railway was operational I used multiple supplementary switches to change point polarity with no switching issues. I used the now no longer available power booster to power the EPL point motors. What I think killed my supp switches was that on several occasions I did back drive the frog with wrong polarity set. While I did have the system protected with fuses, perhaps the fuses were not quick enough to protect the fragile supp switch contacts. One failed leading to a short circuit which at the time I was unable to detect and was partially responsible for me dismantling the railway.

 

[stockers]

Hi, I found the switches put too much strain on the LGB point motor and made it unreliable.

Never met that problem here. and I was not regularly maintaining them - just chucked them in and used them regularly.