Testing Device For DCC Short Circuits?

[jjdamnit]

Hello All,

Metro Red Line

Is there a device that can detect short circuits on a DCC-equipped locomotive before I find out The Hard Way?

The only "device" I know of is a multi-meter or continuity tester; AKA- -"Beeper"- - to "trace" the circuitry before applying full power. 

Just like "testing as you go" with track feeders and power you should adopt the same protocol when installing decoders.

Hope this helps.

[wrench567]

  A current limiting program track should not be able to fry a decoder. But mine did let the smoke out of a plug and pray decoder once. Clearly a faulty decoder because it's P&P replacement is still operating decades later.

  One more thing is to use a multi meter and make absolutely sure the motor brushes are isolated from everything else including the frame. The old P2K end cab switchers had the bottom motor brush hot to the frame. Any minor derailment and a wheel touch the frame and poof. Magic smoke. Proper wiring and soldering is essential to a good installation. Frayed wire ends touching the next pad has been known to blow decoders. Another issue barely covered is vertical space. I've seen decoders fried because the shell squeezing down on the decoder until it touched some metal from the weight of top of motor.

     Pete.

[gregc]

tstage

that's where the ESU decoder tester module would have shined and detected the short prior to installing

no doubt it can verify that the decoder works properly before installing and that there's damage after improperly installing, but it's not obvious how it can detect improper wiring when installed in the loco.

looks like the decoder plugs into the tester giving the tester access to all input and outputs.

a decoder may be able to determine that the motor connections are shorted by applying a lower level output and measuring current thru an h-bridge that has a sense resistor for measuring current.   But i know of no common way to measure current on a digital output pin that might similarly be used to detect a short

[tstage]

gregc

so more likely, there was a short on one of the decoder outputs: motor, LED/lamps, speaker. those could have been tested using an Ohm-meter. while the motor may be in just a few Ohms, it shouldn't be zero (the meter probes connected together)

Then that's where the ESU decoder tester module would have shined and detected the short prior to installing it into the locomotive.

Tom

[gregc]

presumably there was a short in the wiring of the decoder.

i doubt a short on the input side (track) of the decoder would damage the decoder, the short drops the voltage to the decoder to zero and it would be the booster or circuit breaker that recognizes the short and disconnects power

so more likely, there was a short on one of the decoder outputs: motor, LED/lamps, speaker.    those could have been tested using an Ohm-meter.   while the motor may be in just a few Ohms, it shouldn't be zero (the meter probes connected together)

[tstage]

Agreed.  You should ALWAYS initially program and test your decoder installations in programming track mode vs POM.  Your DCC system's short detection will engage and shut down; thereby keeping your decoder from receiving full current and getting fried.

ESU does make a decoder testing module but it's for testing the decoder prior to installing it into a locomotive.  I did a quick review of it, if your interested:

ESU 53900 Decder Tester

It works very well and can test a variety of decoders besides ESU.  You can also use it to program the decoder CVs.

Tom

[maxman]

I thought that was what the programming track was supposed to accomplish.

[ATLANTIC CENTRAL]

Metro Red Line

Is there a device that can detect short circuits on a DCC-equipped locomotive before I find out The Hard Way? I recently fried an ESU LokSound decoder following an attempted install. Fortunately it's under warranty and I'm getting a replacement soon, but I'd like to use such a device for all future decoder installs from here on out.

 

Did you run the locomotive on DC first?

Are you sure you had everything wired properly and insulated from each other and from any metal parts?

There is no "magic box" for this problem.

Sheldon

[Metro Red Line]

Is there a device that can detect short circuits on a DCC-equipped locomotive before I find out The Hard Way? I recently fried an ESU LokSound decoder following an attempted install. Fortunately it's under warranty and I'm getting a replacement soon, but I'd like to use such a device for all future decoder installs from here on out.