Decoder testing?

[7013]

I would never profess to be anything other than a rank amateur when it comes to electronics, but it occured to me that with so many problems posted on various forums regarding wiring, performance and sometimes non working decoders there should be some method of rigging a decoder up to a unit that reads the decoder and fault finds. As I stated I know little about electronics but given that the wires on a decoder are 'standard' NMRA in their function I imagine one having a unit that the wires or a plug can be attached to and read so that the viability of each wires circuit could be checked.

Perhaps I am being naive but in these days of electronic wizardry I am surprised there is no commercially available unit. How many times do we read that 'I wired this up and everything went dead' or 'I followed the instructions to achieve X but X did not happen' . Sadly a significant proportion of decoders become destined for the bin when simply checking them would maybe isolate the problem. Of course a puff of smoke and a funny smell are usually fairly conclusive evidence for consigning a decoder to the bin!

Anyway over to you electronic whizz kids to tell me why this would not be viable.

Maybe there is something available?

[Mod5]

They have been available for some time. Perhaps a look at some of the specialists like Bromsgrove Models or Digitrains web sites will help you.

[Ron Ron Ron]

As Mod5 says, these have been available for almost as long as DCC (15 years or more).

There are several available from companies like ESU, Veissmann, NCE, Digitrax and a number of small manufacturers (e.g. Ulrich -link here- mrr-pr0309_215.ashx ).

Decoder testers did fall out of favour and a few pundits questioned the real need for them when you can easily test all of a decoders functionality on installation in a loco.

Once recommended, they're now considered by some people to be a "geeks" toy and not really necessary.

 

Earlier testers were sometimes quite rudimentary devices, but more recent ones seem to be a bit more sophisticated.

For example, the ESU 51900 , which has a 6-wire NEM 651 and an 8-wire NEM 652 harness interface, as well as a 21-pin mtc-interface and terminals for bare wire.

It also has a built-in high quality, 5 pole skewed armature can motor with flywheel to check the motor output, as well as a 20 mm loudspeaker for testing LokSound-Decoders.

 

ESU 51900 decoder tester

DCC Supplies £35.65

 

The NCE decoder tester is cheaper, but more basic and doesn't have a motor or ability to test sound decoders without modification. It doesn't have facilities for 21-pin decoders either.

Tony's Trains have a guide to modifying this device to add motor and sound features, but it's a bit Heath Robinson compared with the off-the-shelf alternative.

 

Enhancing the NCE decoder tester - Tony's Trains

 

 

p.s. Just a quick Bing or Google is all it takes.

[Edwin_m]

I read the OP as asking about something a little different. The testers on the market attach lights/motors/speakers to the decoder and it is then up to the user to operate these and see if they work.

 

It would also be possible to connect the decoder track feeds, probably via an interface to some sort of computer, and automatically exercise each feature. I presume decoder manufacturers do something like this to check them before they leave the factory, but I'm not aware of anything available to the general public. I guess it would be quite easy to write a script to do this via a SPROG etc, but there is the problem that the behaviour of the decoder depends on the setting of lots of CVs, and a test would probably need these to be restored to default values which may not be what is wanted.

[Nigelcliffe]

Yes, current testers work as Edwin describes.

My own home-brew tester (a row of screw connectors and a few LEDs with series resistors - total cost maybe £2) does the same.

I test decoders using a Sprog - all I need to check is the function mapping and that the relevant LEDs light when function keys are operated. That proves the outputs on the decoder are working. Beyond that, any special arrangements are in CV settings.

 

To test the circuits inside a loco, and not just aftermarket additions where one might expect problems, requires a bit more thought.

I've found grounding issues inside commercial RTR "DCC ready" N stock (most recently two different Farish 108s) which will destroy a decoder but show completely normal and correct running with the analogue adaptor plate in place.

One could test using a decoder with protected outputs (eg. Zimo claim full protection of outputs, and my limited experience shorting them by mistake on the bench suggests the claim is valid).

I now test everything with a multi-meter before hooking up the decoder. I want to know there are no shorts and that current used in any circuit is within sensible bounds. But its a long-winded process.

 

- Nigel

[7013]

Thanks for the replies, and very interseting too, I like the ESU decoder tester, but one would probably only use it if a problem arose, interesting to read about others approach to testing, fingers crossed i have never had a problem with a decoder yet, but I do feel sorry for all those who do get problems, most frustrating, but at least complete electronic numpties like me would have recourse to some sort of testing before bashing it with a hammer! or returning it if warranty allows.

[Sunnysa]

Thanks for the replies, and very interseting too, I like the ESU decoder tester, but one would probably only use it if a problem arose, interesting to read about others approach to testing, fingers crossed i have never had a problem with a decoder yet, but I do feel sorry for all those who do get problems, most frustrating, but at least complete electronic numpties like me would have recourse to some sort of testing before bashing it with a hammer! or returning it if warranty allows.

 

I always test a new decoder in a tester before installing in a loco. Then I know it will work if my installation is correct.

There is nothing worse than fitting a decoder that does not work from the get go.

Over my 15yrs op DCC I have had a few duds from new.

 

Ian

[johnd]

Best Decoder tester I have is a baccy diesel that the body come's of easily don't bother with the screws I use a 47 with lights, alright its 21 pin but with the Bachman adapter 8 pin can be tested.

 

If you used a loco fitted with a 8 pin socket a fly lead from a Hornby Sapphire would enable you test a 21 pin decoder.

 

Just a thought.

[Edwin_m]

Zimo have recently announced a test stand (scroll to page 3), which includes automatic self-test of their own decoders as well as the usual testing features. Basically, as I speculated above, what they use to test the decoder in their factory. It won't be cheap...

[melmerby]

I'm resurrecting this thread!

 

I have just bought an ESU 51900 decoder tester but I am a little puzzled as how you connect up wired in decoders as there doesn't appear to be a connexion for the lights common (blue wire) although it's mentioned in the instructions!

It has connexions for speaker (2 off), track (2), motor (2), front light, rear light and 4 aux outputs, but no common +ve !

Anybody else noticed this?

How do you get around this?

 

Cheers

 

Keith

[Dagworth]

I'm resurrecting this thread!

 

I have just bought an ESU 51900 decoder tester but I am a little puzzled as how you connect up wired in decoders as there doesn't appear to be a connexion for the lights common (blue wire) although it's mentioned in the instructions!

It has connexions for speaker (2 off), track (2), motor (2), front light, rear light and 4 aux outputs, but no common +ve !

Anybody else noticed this?

How do you get around this?

 

Cheers

 

Keith

You don't actually need the blue wire for any of the functions to work, they will all work by grounding them back to either track feed. Just leave the blue wire disconnected.

There is no blue wire on the NEM six pin plug

 

Andi

[GoingUnderground]

Or you push the bare end of the blue wire into the appropriate socket on the 8 pin connection on the Profi-Prufstand/Decoder Tester. If you are going to do this, it might be an idea to put a spot of blue paint next to the relevant socket so that you know which it is for the next time that you need to do that.

[melmerby]

You don't actually need the blue wire for any of the functions to work, they will all work by grounding them back to either track feed. Just leave the blue wire disconnected.

There is no blue wire on the NEM six pin plug

 

Andi

 

 

Or you push the bare end of the blue wire into the appropriate socket on the 8 pin connection on the Profi-Prufstand/Decoder Tester. If you are going to do this, it might be an idea to put a spot of blue paint next to the relevant socket so that you know which it is for the next time that you need to do that.

OK thanks chaps.

 

Keith

[PaulCheffus]

I'm resurrecting this thread!

 

I have just bought an ESU 51900 decoder tester but I am a little puzzled as how you connect up wired in decoders as there doesn't appear to be a connexion for the lights common (blue wire) although it's mentioned in the instructions!

It has connexions for speaker (2 off), track (2), motor (2), front light, rear light and 4 aux outputs, but no common +ve !

Anybody else noticed this?

How do you get around this?

 

Cheers

 

Keith

Hi

 

Mine has a connection for the blue wire but I think it maybe an earlier version as it doesn't have the screw terminals shown in the photos on the ESU website.

 

Cheers

 

Paul

[trustytrev]

Hello,

         Merg do a decoder test rig PMP14 as a Pocket Money Kit @ £1.38. You just have to put it together.http://www.merg.org.uk/forum/stores/info-sources/814.pdf

Some other items that may be of interest.http://www.merg.org.uk/merg_kitlocker/section.php?id=31

trustytrev.

[Dagworth]

Hello,

         Merg do a decoder test rig PMP14 as a Pocket Money Kit @ £1.38. You just have to put it together.http://www.merg.org.uk/forum/stores/info-sources/814.pdf

And be a member...

Some other items that may be of interest.http://www.merg.org.uk/merg_kitlocker/section.php?id=31

trustytrev.

This link doesn't show up unless you are a member and signed in to the MERG forum

 

Andi

[melmerby]

Hello,

         Merg do a decoder test rig PMP14 as a Pocket Money Kit @ £1.38. You just have to put it together.http://www.merg.org.uk/forum/stores/info-sources/814.pdf

Some other items that may be of interest.http://www.merg.org.uk/merg_kitlocker/section.php?id=31

trustytrev.

£1.38 wouldn't even buy the components used in the ESU one!

 

Keith

 

EDIT I have already made one like that from scratch, mine has screw terminals as well as a 8 pin socket!

[melmerby]

Hi

 

Mine has a connection for the blue wire but I think it maybe an earlier version as it doesn't have the screw terminals shown in the photos on the ESU website.

 

Cheers

 

Paul

It may be the new version derives a common +ve internally as there are a couple of diodes and transistors which seem to be across the DCC input and are conected to the LEDs

 

Keith

[Dagworth]

It may be the new version derives a common +ve internally as there are a couple of diodes and transistors which seem to be across the DCC input and are conected to the LEDs

 

Keith

Same as the old one then, although mine has a terminal for the blue wire it also has the diodes

 

Andi