laisdcc DCC decoder: Tim Lowe of the Widget Shop writes...

We have invited Tim Lowe of The Widget Shop to review our experiences of using the LaisDCC decoder, and here is Tim's comments and observations on our experiences.

Firstly, thank you for taking the time to review the LaisDCC decoders on your blog and for providing a useful summary of the process for running a stall current test. Your revised video of the decoder review is much more true to our experience and we appreciate the trouble you've gone to in making it.

If I may I would like to make a few observations which might help clarify a couple of matters.

Stall current testing

An excellent introduction to the technique and I would like, with your permission, to point people to your post when trying to encourage them to run the test. However the meter being used must be able to measure current sufficient for the expected outcome. Some meters are not able to measure more than 0.5A and will pop a fuse as soon as the current flow exceeds the meter's limit.

With regard to your comment about the use of 0.5A decoders for 4mm modellers you will no doubt be aware that modern models using can motors draw far less current than the older designs with open frame style motors. So in the world I model, American outline, it is rare to come across models that draw more than 0.5A peak current. My older more current hungry models, such as older Atherns, get remotored with new Mashima can motors to reduce their current draw. This allows me to run several locos, including multiple unit consists, without having to add additional current booster packs. Indeed, I've just fitted these 0.5Amp 8 pin decoders to two new Bachmann On30 models which dwarf the size and pulling power of older OO-gauge models such as my 40 year old Hornby 'Evening Star'. As your table shows, the current draw depends on a number of factors from motor design, age, wear, maintenance, lubrication, drive train, train load and so on. This is why it is important for all DCC modellers to understand that each installation is different and should be considered as a unique case; one modeller's loco may draw 0.7A whilst another's experience may tip beyond 1A for the same edition of the model.

I found your quotation of Jonathan Edwards' comments interesting. Whilst for new locomotives the draw current will be listed in the locos literature, so matched decoders can be installed, we both know that many modellers have older locos in their fleets and may also modify or remotor locos. It is unlikely that older locos will come with that information in their package documentation as it wasn't relevant at that time. All decoders are rated by peak and constant current draw and must be matched to the installation because, as you've found out, a mismatch can result in a blowout. With decoders rated from 0.2A to 2.5A and higher you can't just fit any old decoder to any loco. Hence my surprise at his comments. To work out the match the owner must carry out a stall current test. As you've shown its not that hard, the kit isn't expensive and is probably already in most railway modeller's toolkit.

Motor tuning.

Another facet of installations to which you allude is the performance of a loco when using different decoders with DCC. The Laisdcc decoders have a number of CV's specifically to alter the performance of a motor. The motors in model trains are designed to run on DC current but DCC overlays an AC signal which causes some motors to behave in different ways. Tuning motors under DCC is a bit of a black art. Many decoder manufacturers try to simplify the process by offering their products preprogrammed and providing limited opportunities for clients to change the settings. Others offer a basic setup and lots of options for people to fine tune the running of their locos. Laisdcc decoders offer access to a number of CV's for the enthusiast to use to modify how their locos run. So using the range of CV's available I can tune two locomotives that spend their time consisted together so that their performance is identical; no pushing or pulling between them across the grades on my layout. As a starting point, if a newly installed decoder makes the model stutter the 'back EMF' setting could be disabled. This corrects the stutter in most cases. However there are further settings to experiment with and no one installation will necessarily be the same as any other. A good starting point on this complex area might be https://sites.google.com/site/markgurries/home/technical-discussions/decoder-motor-drive/back-emf-bemf

Laisdcc decoder review.

Laisdcc are now manufacturing with their own unique NMRA issued manufacturer's ID of 134 and from the end of March their decoders will have this set in the firmware. As previously discussed these decoders were originally built under contract for other 'manufacturers'. So the manufacturer's ID was never set in stone and should not be used as a guide to the 'origin' or otherwise of the installed firmware. Some commentators are referring to likenesses and perceived firmware similarities without bearing this convoluted manufacturing reality in mind. The current beta version of the full manual for these decoders is now available at

http://tiny-smart.com/LaisDcc_Decoders_Manual.pdf

The CV list does not need to be implemented in full as not all the settings will be relevant. Also, CV's can be programmed from the throttles provided by DCC system manufacturers by following the instructions provided with the DCC system. Devices such as the SPROG, LocoBuffer (I use this one) or the system manufacturer specific devices (e.g. Digitrax’s PM4, Lenz LI100) that connect DCC systems to computers will make programming decoders easier, and I would recommend this approach for anyone with a larger fleet of decoders or intending to go further and install accessory decoders on their layouts, but they are not necessary or required for any decoder programming.

Some 'how to' instructions on programming CV's with Lenz Compact systems can be found at http://www.newrailwaymodellers.co.uk/electrics-dcc-decoder-programming.htm

You should note that you have used the lowest current capacity devices offered by Laisdcc for your trials. The Widget Shed carries stocks of their 8 pin 1A peak current decoder and their bare wire form factor of the same device and these will be more suitable for your audience. Laisdcc are shortly to announce 2A peak current decoders in a range of form factors and we are keen to see these as we have a lot of demand from the UK outline modeller's for this capacity of decoder.

Finally, The Widget Shed is able to take back decoders in what ever form they are returned, even with the wires clipped back or where lighting functions have been damaged, but we can only offer replacements if the decoder can be made to function in some way when we test it. At some point the customer has to take responsibility for their use of their purchase and total failure due to burnout seems fair to us. As you know we will help customers where we are able with advice and some support but as we are not physically present to run the tests and perform the installation we can only do what we can.

I hope that when you've reviewed the manual this goes some way to reassuring you that these are capable decoders and that the manufacturer and their leading suppliers are supporting to you, the customer, and listening to your concerns and comments. I look forward to hearing from you soon and wish you a peaceful Easter and happy railway modelling.

All the best,

Tim and The Widget Shed Team.