# Max voltage - Minimum mA for EPL's



## Merlin83 (Sep 23, 2011)

Hello,

What is the minimum voltage I can switch an EPL turn out switch on with ? And is there a minimum mA I need to 'throw' and hold the the switch with ? 

I have seen recommendations for *DC *and *AC *- usually half-wave if it's AC - so can I build up a simply relay with a power supply in series to throw the EPL switch, if so - how should I size the power supply ? Could I use a 24 VDC 1 AMP power supply with a properly sized relay for that voltage and 'holding current' for the coil of the relay, perhaps have a NO relay which when energized closes, and switches the EPL turn-out - power is switched off the relay open and changes back to NO state. I was thinking of having a small pilot duty relay drive a larger relay with the power supply in series to do this.

So to sum it up - what's the min/max voltage for switching EPL turn-outs and how much current can or do I need to drive the EPL 'motor' ?

Oh, and please correct anything I have said above if it's all totally wrong.

Thank You,
Brett


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## Greg Elmassian (Jan 3, 2008)

I'm a little confused with your description of the relay. 

" so can I build up a simply relay with a power supply in series to throw the EPL switch" 
sure.... 

" how should I size the power supply " 
you need enough current for the relay and the turnout... but are you talking AC and the same supply for both, or DC or what? 

I believe the LGB turnouts just take a pulse, not constant power, so using a relay does not make sense... you need a momentary circuit. 

I'll let an LGB expert weigh in here, to make sure that statement is right... 

Also, worrying about the minimum current or voltage is not a good idea, if the turnout gets "sticky" it will take more current... you want to come up with a "nominal" supply... 

Greg


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## chuck n (Jan 2, 2008)

For a number of years I used EPL switch motors on my railroad in Denver. It requires a AC source. I was not happy with the AC output from the terminals on my power supplies. Someone at the Denver club suggested getting a 24v AC transformer at a hardwear store. These are for lawn watering systems. It worked great. As Greg said it is the instant pulse, not a continuous feed. This came up a while back an someone said that a lower voltage ~18v would work. Just make sure that you are using an AC output. LGB made a controler for these machines. they are a momentary on/off, up throws the motor one way and down throws it the other. Chuck


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## toddalin (Jan 4, 2008)

If you use half wave a/c, you need a bit more voltage than filtered dc. You can do fltered dc down to less than 12 volts (maybe even 8 volts), but for half wave, a/c you probably want a minimum of 14 vac. Because you only pulse the ELP motors, they should handle up to 24 volts without problem. They can handle half wave continually, within reason.

They typically draw about 1/2 and amp, but can probably exceed an amp if jammed. Lots of people just use a doorbell transformer/diode.

I use a 16.6 vac half wave with a "cap kicker" and the transformer has a 16.6 amp capacity (but I fuse it at 10 amps). But I do throw as many as 20 turnouts at a time to reset everything to default position.


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## TheRoundHouseRnR (Jul 15, 2012)

I use DC voltage but as stated above, they can only take a pulse of DC or they will burn up. I use a 24 volt transformer to a 2400uf capacitor in series with a resistor to limit current and to act as a basic timer. Then i use a darlington transistor to dump the voltage. The transistor can switch current with a very low base current, meaning you can use reed switches and they never burn up unlike the original epl system. 

When the transistor is activated it sends a pulse of DC voltage to the epl and drains the capacitor.The resistor keeps from burning up the switch and only sends a pulse each time its activated. 
If the value of the resistor is changed you can shorten or lengthen the recharge time of the capacitor 

Since using DC i would never go back to half wave AC. I never had a epl miss a beat to date since switching over, never had a reed switch burn out and i get a nice smooth snap out of them. 

The Roundhouse RnR


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## TheRoundHouseRnR (Jul 15, 2012)

By the way i switched up to five at a time off one capacitor.


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## kormsen (Oct 27, 2009)

i use the epl system with reed contacts. 
the normal 16V AC output of the LGB powerpacks do just fine. 
the switchmotors should need just a short impulse. they are designed to keep position by mecanical properties. 
the only problems i experienced are burnt out reeds. - but only if i hook up more than two switchmotors to one reed.


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## Dan Pierce (Jan 2, 2008)

LGB sold a 16 volt 1/2 amp wall transformer to handle the EPL drives. 
I found this not enough energy at times so I added the LGB booster and now I have no problems on my outdoor layout. 
Indoors I used my own method of momentary push button switches and d1 amp iodes with an 18 volt transformer. I can operate 2 EPL's at the same time with no problem.


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## krs (Feb 29, 2008)

The preceding posts cover things pretty well.

If you use DC you need to make sure that you don't power the turnout continuously or you might burn out the coil. That is especially true for the older versions.

With AC, you use half-wave rectified AC, at 18 VAC that can be applied continuously - the turnouts are designed to handle this.
This would happen for instance if you use a reed switch operated by a magnet on the loco if the loco stops over the reedswitch and keeps power applied continuously.

In either case, since this is a two-wire control system, you need to apply a positive voltage to throw the turnout one way and a negative voltage to throw the turnout the other way.

The actual voltage needed depends on the length and gauge of wire between the voltage source and the turnout.

This is a low cost arrangement - I think it's a drawing from Maarten in the Netherlands looking at the way the components are drawn.
DC source of about 24 volts, DPDT switch, "M" is the turnout motor:










If you have a very long run between the controller and turnout, you can use this arrangement:










Left side shows the turnout control with a non-polarized capacitor (or two electrolytics back to back) mounted close to the turnout.
(Right side are just LED indicators)
I tested that arrangement with a 1000uf capacitor - the turnout threw reliably with up to about 120 ohms in the control lead.
A bit unconventional, but it works well for long control lines.

Knut


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## Dan Pierce (Jan 2, 2008)

Personally I would never tie polarized capacitors back to back as they would tend to divide the voltage and one or both would go bad (blow up, short) 
If this was needed and a non polarized cap can not be found I would at least install diopdes across the capacitors to eliminate the reversed polarity that can occur across each one. 

I know people get away with some things in electronics like no limiting resistors for leds, no noise filters on regulators and no diode protection on capacitors and relays, but that does not make it right, however it is your house and trains, do what you want.


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## Merlin83 (Sep 23, 2011)

Gentlemen,

Sorry for confusing post - and thank you for the follow up responses so far. But, here's what I am wondering about - I have many of the (German made) LGB momentary control boxes. And they work fine, but I want to use a separate relay board, something like this *http://tinyurl.com/cnbdqy7* - why? Well I work with industrial automation equipment all day long and work with a protocol called Modbus - I have a front end controller from which I can send signals to open and close relays, monitor sensors, monitor current & voltage, etc.

So, even though what I want to do is readily available - I wanted to 'tinker' with doing in way I could learn something. I have been also working with an Aurduino board to try different little experiments,etc. - So, is it a fair statement to say that I can 'blip' through a momentary switch half-wave rectified AC @ 18 volts to move the EPL motor back and forth ? - The LGB momentary control box does this for me, and I have contemplated dong a 'tear-down' to see what's inside the box, and then replicate on a bread board or use Express PCB and make my own. I am quite handy with my Weller soldering gun - so any insight or guidance is most welcomed!

Thank you,
Brett


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## toddalin (Jan 4, 2008)

Posted By Merlin83 on 04 Dec 2012 11:07 AM 
Gentlemen,


So, is it a fair statement to say that I can 'blip' through a momentary switch half-wave rectified AC @ 18 volts to move the EPL motor back and forth?

Thank you,
Brett


Yes, I do it all the time. I use 555 chips to trigger the relay and set the duration for ~3/4 second so the turnouts have plenty of time to throw regardless of how fast the trains run through. I also use the momentary relay that throws the turnouts to set a "self-latching" non-latching relay to turn on that block while releasing the prior block. This block relay releases when the next "trigger" occurs.

It is _*very important*_ that a train not be allowed to trigger a turn-out when another train is already triggering it, such as if you park the engine with the magnet over the reed switch. If the turn-out receives both "signals" simultaneously and they are for different directions, you create a differential voltage that is the sum of the two half waves!

Because I use "cap kickers," I put ~22.5 volts + and - to the turn-outs, that quickly bleeds down if a turnout remains activated so as not to damage the turnout motor. In a prior design where I did not "lock out" the trains from activating two reeds simultaneously, it did happen where a train parked over a reed creating a differential of 45 volts across the turnout. This instantly smoked the circuit board.

My triggers include reed switch/magnets and track gaps that work with any engine or railcar with metal wheels depending upon the required application.


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## kormsen (Oct 27, 2009)

Posted By Merlin83 on 04 Dec 2012 11:07 AM 
- So, is it a fair statement to say that I can 'blip' through a momentary switch half-wave rectified AC @ 18 volts to move the EPL motor back and forth ? - The LGB momentary control box does this for me, and I have contemplated dong a 'tear-down' to see what's inside the box, and then replicate on a bread board or use Express PCB and make my own. 

i had one of the epl boxes open and there were very few things in it. i made my own "epl" system. AC to two diodes(one backwards), from there to two bellbuttons, from there with a common wire to the switchdrive. or, where i wanted to activate more than one switchmotor with one push, AC to the button, common wire as far as convenient, than splitting the wire for the different switches, a diode before uniting with the wire from another button, and on to the switchmotor. (this second option comes handy for passing-sidings and yards) concerning reeds, they either replace the pushbuttons, or are on a paralell wire to them. i try, never to hook more than two users to one reed.


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## TheRoundHouseRnR (Jul 15, 2012)

The OP never mentioned using reed switches. However if the intention is to use reed switches, using the method i explained with a darlington transistor to switch the load. You can wire as many switches as the transistor will handle, which i have yet to find that number. 
I have switched 4 epl motors with a single reed at a train display for days without a heatsink. I use security alarm window reeds. They fit perfectly between the ties and are cheap. They also have two screw terminals built in for the wires. Makes it really nice when your setup is always changing. 

So reed switch failure is the only down fall to previously mentioned wiring. If not using them , i would say go with their ideas, its easier. If you want to use reeds go with the transistor. I do train displays and I can't afford a high balling F7 diesel to ram into the back of a parked train do to a cheapo reed switch failure. 
The Roundhouse RnR


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## kormsen (Oct 27, 2009)

Posted By TheRoundHouseRnR on 04 Dec 2012 03:44 PM 
...I use security alarm window reeds. They fit perfectly between the ties and are cheap. They also have two screw terminals built in for the wires... 

now it's getting interesting. please explain a bit more detailed. i thought, that these alarm reeds make contact, when one takes away the magnet.
(concerning your other points - i don't believe in telling people what to do. i prefer telling them, what worked for me.)


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## Dan Pierce (Jan 2, 2008)

Relays can be NO Normally Open, or NC Normally Closed. The magnet puts the reed to the opposite state. I know most of us already knew this, but some readers may not.


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## Trains West (Oct 4, 2008)

some more info to help people understand how to operate tunouts

http://www.trainweb.org/girr/tips/t..._tips.html


if you are using ac with diode routeing i would run more like 24 volts ac becouse half wave will only give the power of like 12 dc if you do 18 volt ac it will be like 9 vdc

the other thing is the machines need to be free moving to operate well 

and yes only take a moment of power do *NOT *apply constant power to an lgb switch motor


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## TheRoundHouseRnR (Jul 15, 2012)

The sercurity alarm reeds that i have bought are Normally Open Reeds. Not sure if they are all that way but mine are. They are from a cheep harbor freight alarm system. It was only able to protect two windows or doors. You would think they would be normally closed and all wired in series. That way when one breaks the contact, the alarm goes off. These however are not, i never tested any others. 

Im really sorry if you feel that I'm "telling people what to do". I felt my post did not come off that way. 

I simple shared that in my experience and others also that reed switch failure is a down fall to this system. Even a reed switching one epl motor can fail when they are taking the brunt of the load. This is why i use transistors. I simple made the suggestion that i would go with this method to save yourself some headache and money. 

If you felt that i was telling people how to do something because of that, I appologize. I really felt that i was not being that way and i thrive not to. Anyone can do as they wish. It is their railroad. Cheers 
The Roundhouse RnR


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## Trains West (Oct 4, 2008)

_You would think they would be normally closed and all wired in series. That way when one breaks the contact, the alarm goes off. These however are not, i never tested any others. _



that is how simple alarms work ..... the reed is held closed by the magnet if anything happens to move the magnet away from the reed the alarm goes off 



the transister is a good idea to boost the current capacity of the reed ... a small relay will do the same 

my only complant about useing reeds to control switchs is that every locomotive must have a magnet on the bottom to trigger and big enough so you get a good long trigger

using the pic chip should help as you should be able to do more like if this one swich is in thrown state then change switch b to open and it could trigger on a smaller trigger and still close the turnout


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## TheRoundHouseRnR (Jul 15, 2012)

That is the nice part about the capacitor discharge before the transistor. The train can fly over the magnet at full speed and it will still throw the same way as if it was going turtle speed. I agree about it being a pain to install magnets on every engine. I usually put them on cars. There are other ways around using magnets. Like photo cells and track gaps using the cars metal wheels to bridge the contracts. More than one way to skin a cat as they say. 
I also have a schematic to use photocells and lgb switches. 
The Roundhouse RnR


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## Trains West (Oct 4, 2008)

not sure photo cells and outside are a good idea ...... yes lots of ways it can be done ....my goal is fewer parts is a better system


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## TheRoundHouseRnR (Jul 15, 2012)

No they are not a good idea outside except maybe in a tunnel. I did'nt mean to imply outside. Just as an option. I was unaware that we where talking about outside only. Sorry. 
The Roundhouse RnR


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## Trains West (Oct 4, 2008)

no sorry ..... it is xmas time guess i should relize that right now there are a lot more indoor railroads .... just at least in my neck of the woods there are no indoor g-scale railroods we are all outside so it is what i am used too


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## kormsen (Oct 27, 2009)

Posted By TheRoundHouseRnR on 05 Dec 2012 08:07 AM 
The sercurity alarm reeds that i have bought are Normally Open Reeds. 

thank you, for clearing that. i thought, that all security reeds are held open by the nearby magnets and make contact, when the magnet is moved away. 
about the other point, put it down as me being thin skinned. 
I agree about it being a pain to install magnets on every engine. 
but there are advantages too.
you can have trains with or without magnets, that "behave" different. you even can position the reeds and magnets differently. i tested additional magnets and reeds on the right and on the left side of the loco cabins. 
(btw, the magnets i'm using are from kitchen furniture. about one inch long, a quarter wide and a sixth thick) 
Like photo cells and track gaps using the cars metal wheels to bridge the contracts. 
both are at a disadvantage against reeds. they work wth every train/every metalwheel that passes. 
on my last layout i used the "belt and braces" aproach with the reeds. just installing two reeds for every function. about half a foot apart one from the other. 
every now and then i checked, if the switchmotors buzzed twice, for knowing where to replace a reed.


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## toddalin (Jan 4, 2008)

Posted By kormsen on 06 Dec 2012 05:11 AM 
Like photo cells and track gaps using the cars metal wheels to bridge the contracts.
both are at a disadvantage against reeds. they work wth every train/every metalwheel that passes. 


Track gaps and reed switches serve two different functions and are not necessarily synonomous in their use. 
You use a reed switch when you want a single pulse, such as to activate an LGB turn-out motor. A track gap could fill this purpose but every wheel would pulse the turnout. That's not a bad thing in every case.

But take the case of a "leap frog" where a train stops and releases another train. In this case a track gap is not what you want!

When a train would return, it's first wheel will contact the gap stopping the train and releasing the other train. So the other train tries to leave, but the back wheels from its engine now hit its gap (it stopped with the gap between the trucks) and the train stops with its engine now sticking out into the traffic releasing the other engine. So the other engine now tries to leave and its back wheels hit its gap and stop the train releasing the other train and etc., etc., etc.

Where a gap does shine is where you want to be sure that an operation is being performed and there is to be a "time out." For example, at a crossing you want one train to stop to let the other pass. You want to be DEAD SURE that the train will stop and don't trust a single pulse of a magnet/reed. But the gap will detect the engines wheels, and all of the railcar wheels and there is lots of redundancy assuring that that train is going to stop. This is also a good idea for a reverse loop circuit where you want to ensure that the polarity was switched.

Also, with a gap, if you back through the crossing, your last car will trigger the gap so long as it has metal wheels.


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