# Need circuit breaker or short sensor for power project



## JamesNJ (Nov 18, 2016)

Hello all,

I'm looking around for a button style circuit breaker used on DC power supplies, or perhaps a short circuit detection gizmo I can use to break power to tracks/blocks when trouble hits.

I've been doing some research into better and more cost effective power supplies. I started down the route of using arduino PWM to power a DC setup, only to find that it is not so simple (but haven't given up yet). I have found some interesting pre-built 12v PWM motor controllers that have promise, but the one thing all of these solutions seem to lack is some kind of simple circuit breaker or current sensor to help cut the power when shorts occur.

The little button breaker on the back of my Kato PSU seems adequate, but maybe there is something better someone can suggest. Open to any ideas, but more importantly if you have part number recommendations that would fit nicely into a typical DC setup that would help.

Right now I have a small (non-permanent) layout that I run 1 loco on but am thinking something a little larger with 2-3 locos and experimenting with other gizmos like location sensing, signals, etc.

Thanks!


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## rrjim1 (Mar 12, 2015)

When I used DC a long time ago, I used a auto reset circuit breaker at the power supply and a auto lamp in my throttles. All Electronics surplus sells one that trips at 1.6 amps, and will auto reset when the short is removed. If you want one with a button you should be able to find some at a Electronic Supply Co.


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## highvoltage (Apr 6, 2014)

JamesNJ said:


> Hello all,
> 
> I'm looking around for a button style circuit breaker used on DC power supplies, or perhaps a short circuit detection gizmo I can use to break power to tracks/blocks when trouble hits.
> 
> ...


Take a look at these. 3 through 8 amps, up to 32 VDC:

https://www.delcity.net/store/Thermal-Push-Button-Breakers/p_539615


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## RT_Coker (Dec 6, 2012)

The cheep solution is a 12 volt auto bulb in one of the lines from power to track. A short will cause the bulb to light up and drop the voltage to the track.
There is a friendly “DCC++” effort that uses the same kind of boards and they are using short-detection. You can find them here: http://www.trainboard.com/highball/index.php?forums/dcc.177/.
Bob


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## gunrunnerjohn (Nov 10, 2010)

If I were using PWM from an Arduino to drive the tracks, I think I'd do the current sensing in the Arduino, that keeps it all in one place and you can instantly react to any over-current.


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## traction fan (Oct 5, 2014)

*Light bulb*



RT_Coker said:


> The cheep solution is a 12 volt auto bulb in one of the lines from power to track. A short will cause the bulb to light up and drop the voltage to the track.
> There is a friendly “DCC++” effort that uses the same kind of boards and they are using short-detection. You can find them here: http://www.trainboard.com/highball/index.php?forums/dcc.177/.
> Bob


James;

I agree with RT_Coker's idea above. The N-scale club I once belonged to used this method on 20+ transistor throttles that powered the many blocks on their railroad. If you had a short, the light bulb came on and gave an obvious indication that something was wrong. As RT_Coker says, it also dropped most of the track voltage, and stopped the train. The club was using DC. This was before DCC came on the scene. 
As for circuit breakers, you will need to measure the current your trains draw. This can be done with a multimeter, set for DC amps, and hooked in series in the middle of one track feed wire from your power source. A typical N-scale locomotive usually draws about 1/2 Amp. That's well below the rating of most re-settable circuit breakers. You would need the breaker to trip at approximately twice the normal current draw, or a bit above "stall current." Stall current is the higher current level drawn by a loco that is held down on the rails so the wheels can't turn.
You may have difficulty finding a re-settable breaker with a low enough trip rating. Here is another source for circuit breakers. www.allelectronics.com .

good luck;

Traction Fan:smilie_daumenpos:


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## JamesNJ (Nov 18, 2016)

Thanks all for the help. One of the problems I've had is finding a circuit breaker that is small enough to trip on track shorts. I'll admit, even the Kato PSU very rarely trips. This one looks like a candidate:
http://www.allelectronics.com/item/cb-0650/0.6a-circuit-breaker/1.html
I'll have to get one and try it out (BTW, I like that All Electronics site, thanks).

I like the idea of the safety bulb! I assume from your descriptions that the 12v safety bulb is wired in series with the motor (track). I'll definitely play with that idea.

gunrunnerjohn - I agree, one could do it all from the arduino however I'm not well versed in current sensing logic and will need to play with something. Do you have any suggestions on sensors I could try? I found a few hall effect sensor circuits made for arduino, but have no experience with how well they work.

Thanks all,


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