Hi! Just wondering if anyone knows of a way to prevent burning out an electromagnet? I want to use one to uncouple wagons on a model train set, however I think that by the time I reverse the loco direction to uncouple, the electromagnet may burn out.
As I have kids using the set as well, I thought this might be a good safety feature to include. TIA.

 

Electromagnets are usually quite robust, being just coils of insulated wire.
The primary enemy is heat, keeping the current level within limits, and / or limiting the 'on' time of the coil will prevent damage.

 

Electromagnets are usually quite robust, being just coils of insulated wire.
The primary enemy is heat, keeping the current level within limits, and / or limiting the 'on' time of the coil will prevent damage.

Thanks for your reply. I am a complete noob with this stuff. How do I determine what the "current level within limits"?

 

Thanks for your reply. I am a complete noob with this stuff. How do I determine what the "current level within limits"?

If this is a ready made electromagnet then look at its specification. It will include, at least, a rated voltage. As long as you do not exceed that voltage it will not overheat.

 

If it only needs a short pulse to uncouple the wagons then perhaps a capacitor-discharge circuit could be used. The cap would charge relatively slowly via a resistor from the supply, but would discharge quickly into the electromagnet coil. Even if the kids held down the 'magnet on' switch for a long period, there would be only a low prolonged current through the coil.

 

Do you have an actual electromagnet that you are thinking of using? And where would you need to place it? Details really improve your odds of getting good advice. I like Alec's idea. It could be fairly simple to implement (capacitor, resistor and switch) but the devil is in the details.

Also, placement of the EM could aid in safety - place it where it's hard to touch but I don't know enough of your setup to suggest anything.

 

Do you have an actual electromagnet that you are thinking of using? And where would you need to place it? Details really improve your odds of getting good advice. I like Alec's idea. It could be fairly simple to implement (capacitor, resistor and switch) but the devil is in the details.

Also, placement of the EM could aid in safety - place it where it's hard to touch but I don't know enough of your setup to suggest anything.

The following information is all I can get from the manufacturer:

A useful remote operating feature for use with ELC couplings NR-102, which are easily modified by adding the unobtrusive Coupling Lift Arm (available separately NR103 ).
The uncoupler attracts the steel lift arm downwards, pivoting the coupling upwards.
There are no moving parts, it works by creating a temporary magnetic field under the coupling.
A 16v AC power supply such as Gaugemaster T1 or M1 and a non-latching push button switch such as A281-21 are required.
The electromagnet means that uncoupling takes place only when required, at other times the trains run through unaffected.
Installation is simple, just drill a small hole in the centre of the trackbed and fit the unit under the baseboard with two screws.

Is there a way to maintain the EM affect until I can get the kids to shunt away? May only take 5 - 10 seconds. Thanks.

 

Looks like you are going to need a 5-10 sec timer controlling a relay (or perhaps triac) to switch an AC supply to the electromagnet.

 

Since it's under the track bed, will the kids even be near it? If they are, you can build a small box to enclose it. I'd say it's very safe.

It sounds like you hold the switch closed for the duration of uncoupling (I bet 5 seconds is way long). The T1 is a 1A 16 VAC transformer. Easily controlled by a simple switch or relay. This module will allow you to control the amount of time the transformer would be on. There are lots of similar ones on ebay/amazon.

 

Since it's under the track bed, will the kids even be near it? If they are, you can build a small box to enclose it. I'd say it's very safe.

It sounds like you hold the switch closed for the duration of uncoupling (I bet 5 seconds is way long). The T1 is a 1A 16 VAC transformer. Easily controlled by a simple switch or relay. This module will allow you to control the amount of time the transformer would be on. There are lots of similar ones on ebay/amazon.

Thanks for the info. I have bought one of these today. It seems to be what I need. Will need to investigate why you have to use two power sources; that I don't understand.

 

The relay module itself needs 12 VDC power for the timer and relay coil. The relay contacts control separate power, it can be AC. Your EM takes 16 VAC, I believe. Though it might work ok on 12 VDC, worth trying then you can use one power source.

 

Thanks to those who have given me some of their expertise. Just a quick follow-up question. How do you increase the strngth of such a small EM? As it is, this doesn't seem strong enough to lift the coupling.

 

More turns of wire or higher voltage. What are you feeding it now - AC or DC? Voltage level?

 

As it is, this doesn't seem strong enough to lift the coupling.

Have you got the NR103 coupling lift arm fitted to the coupling?

 

Have you got the NR103 coupling lift arm fitted to the coupling?

Yes I have. The couplings will lift if I use small rare earth magnets. In fact they make the wagons do a wheelie. See the attached images. However the Peco EM doesn't make the coupling lift at all.

 

Are you giving the EM 16VAC?
Can you reposition the EM plunger end nearer the coupling?

 

Are you giving the EM 16VAC?
Can you reposition the EM plunger end nearer the coupling?

I haven't tried the 16VAC. I thought it had to be 12VDC. And yes, there is the opportunity to move the plunger closer, however at the moment it is at sleeper height. Lift it up and it becomes too obvious. Still, it's worth a try.