# Way to protect your decoders against transients on DCC



## rreiffer (Jan 14, 2009)

If you are worried about over-voltage transients on your DCC line there is a device called Transient Voltage Suppressors (or Transil Diodes). They come in a variety of voltages and are basically a back to back Zener diode configuration. By putting one of these across the leads inside your engines you can protect against an over voltage in either direction. They can absorb up to 1500A for a short duration. The series to look at is the 1.5KExx series. The xx stands for the voltage. 

Has anyone tried it? I have ordered some (very cheap) to see how well they handle the line voltage spikes (quite often visable on an scope). I ordered 1.5KE24 for my engines. Thoughts, ideas?


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## Cougar Rock Rail (Jan 2, 2008)

Interesting that you are getting voltage spikes...what system are you using? 

I've never heard of anyone having problems with spikes, although I know there are lots of decoders that are underdesigned when it comes to handling the NMRA specified voltages for large scale. 
I've never heard of people having problems with decoders from Massoth, LGB, or Zimo, as they are well designed for self-preservation, but I sure have seen lots of failures from those using NCE & digitrax. 

Keith


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## krs (Feb 29, 2008)

Posted By rreiffer on 13 Jan 2012 02:44 PM 
I have ordered some (very cheap) to see how well they handle the *line voltage spikes* (quite often visable on an scope). I ordered 1.5KE24 for my engines. Thoughts, ideas?

Line voltage spikes?
Is that really what you meant to say?
I assume you are seeing spikes on the DCC waveform and I sure hope that they are nowhere near the magnitude of typical line voltage spikes.


Also...the 1.5KE24 is a uni-directional suppressor; wouldn't you be better off with a bi-directional one like a 1.5KE24C?

And finally I'll echo Keith's question - are you actually having problems in that the DCC decodersyou use can't handle the normal spikes one gets on the track?

best regards,

Knut


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## rreiffer (Jan 14, 2009)

Sorry, it is the 1.5KE24C. I have not seen spikes but for 50 cents, is it worth it for the protection in case of a failure of a booster? Just asking.


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## Greg Elmassian (Jan 3, 2008)

Uhh... what is causing you to worry about this? 

You infer you have looked at your DCC signal with a scope. What voltage are your spikes you have observed? 

have you considered the capacitance that these add and the effect on the DCC signal? 

I think you don't want to clip at 24 volts, think that it might try to clip too early, given the tolerances of the unit. (21.6 min clipping voltage from the data sheet), I would go up the next voltage step, 27 volts for you.. I would go to 30 if I was considering for myself. 

Greg


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## rreiffer (Jan 14, 2009)

Greg, the ever consummate power guy! You have got to love it. Thanks for he tip. Actually it was not really a worry but more of a theoretical idea. It started out during an investigation of using one of these to safely limit the input voltage on the MRC series of decodes.


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## Greg Elmassian (Jan 3, 2008)

I figured as much Rich! 

So, you are dropping with regular diode strings, and then protecting with these? 

Not too bad of an idea, but my opinion (just an opinion based on a modicum of experience with the MRC AD324) is that they have issues not necessarily on voltage, but they get locked up in decoding commands, and then self destruct, usually with a pop and some nice smoke. Have about 12 or so of them, and have killed about 5... I purchased for $12 so I don't care. 

Greg


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## Dan Pierce (Jan 2, 2008)

Greg, you win!! I only destroyed 1 MRC, but I did fix 2 by replacing the mosfets. And the LM style regulator gets hot and needs a heat sink for my 24 volt power.


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## rreiffer (Jan 14, 2009)

Greg, thanks for the feedback. I too picked up a bunch for $12 each and I want to put these in engines I rarely run (and hence the experiment with low cost sound and low cost decoders). I will let you know the results of the whole experiment once the final parts come in.


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## Greg Elmassian (Jan 3, 2008)

Dan, I do run higher voltage than most... often the onboard regulator blows up, or the output, but most of my failures have been when consisted, and one unit gets scrambled and runs in the wrong direction... dunno if that meant a much higher power draw and self destruction, but at $12 each, they are pretty much disposable. 

Bought them until I settled on the "good" decoders for the F3's (I have 10 of them)... will either be Zimos or the upcoming QSI. 

I need to hear the Zimo F3/7 sound file first. 

Greg


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## Axel Tillmann (Jan 10, 2008)

What is QSI


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## Greg Elmassian (Jan 3, 2008)

What I have in the majority of my DCC locos. 

The company with, no offense, better sound files. 

If Zimo had the breadth of sounds that QSI has, I would switch completely, even though the programming is more difficult. 

Greg 

(you just HAD to ask huh? It's the truth, and you know I like the Zimo hardware)


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