Geoff, in addition to opening the door to whole 'nother world, you may think that perhaps you've opened a can of worms as well ...

I've always been "interested" in doing these sorts of things; but honestly, have never actually gotten around to doing it ... just so many "unknowns" from the initiates perspective.  So, now that you have posted something that looks useful in-and-of itself as well as something that has huge expansion possibilities for future applications; I am seriously thinking of testing the waters ....

I've looked at the components that you have listed ... and they are available and not too expensive.  What I have questions about are the "extras" that you and others probably don't give much thought to (just reach in your bins and pull out what you need); but for someone such as myself, there are too many options to make an educated choice.  Could you perhaps make some recommendations as to what types of components I should procure to complete the project?

1. Capacitors.  These come in many flavors (ceramic, film, aluminum, etc. as well as different tolerances) and I'm not sure which flavor is best for this application (C6 (220uf 25V) has been included in your parts list):

• C1 (22uf 25V)
• C2/C3/C4/C5/C7 ((0.1 uf 25V)
• C8 (270 pf)

2. Resistors.  You specify that all are 1/8 W; what sort of tolerances should I be looking for?

• R1-R16 (10K)
• R17 (5K)
• R18 (1K)

3. Diodes. The Schottky Diodes (D1 and D2) are included in the parts list.

• D3 (1N4152-ND) is listed as an "obsolete item" at Digi-Key ... any suggestions for a substitute?  It seems to be available from other sources though ....

4. LED's.  Any recommendations?

5. Board ... ugh!  Double sided?  Plated through hole?  Pitch?  Pads? .... Any recommendation?

Sorry for the noob questions ... perhaps I need to learn a bit more of the basics before jumping in?  Dave O

Dear Dave HVT,

As an Educated Guess, I'm going to say (on Dr Geoff's behalf) Yes.

based on the following:

- Logix is a macro/scripting language which works within JMRI.
It is effectively Input/Command hardware and Output/action hardware agnostic

- At it's simplest, Logix allows "If Input Condition A = true, then do something to Output A" behaviour.

- As far as Dr Geoff's decoder is concerned,
it does not care what the device is that is sending a command,
as long as the command is sent in "DCC language",
and is validly addressed to the decoder/channel in question.

- Ergo, as long as your JMRI rig (PC hardware + JMRI software)

is talking to your DCC command station/booster hardware 
(IE Logix is able to "speak correct DCC language")

and the Logix script itself is written and running correctly

Then there should be no reason why a Logix script can't trigger a response from Dr Geoff's decoder.

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Mr. Bunza,

​That is rather brilliant.  Arduinos are great fun.  I have been trying to work with one to make it onto a route controller.  But have gotten stuck.  If you wouldn't mind, drop and email.  Amazing work, simply amazing!

Jason R.

jasonlreis (at) Hotmail {d0t} com

No problem Dave, I constantly told my boys and my students "questions demonstrate interest... They are one way to learn."

Could you perhaps make some recommendations as to what types of components I should procure to complete the project?

You bet! First, there are really no super critical components used. So my first recommendation is buy cheap! These should work fine: Digikey example parts

P5149-ND          CAP ALUM 22UF 25V 20% RADIAL  0.20

445-8421-ND     CAP CER 0.1UF 25V 10% RADIAL   0.29

BC1018CT-ND    CAP CER 270PF 50V 5% RADIAL   0.35

CF14JT10K0CT-ND  RES 10K OHM 1/4W 5% CARBON FILM  0.10

CF14JT5K10CT-ND   RES 5.1K OHM 1/4W 5% CARBON FILM  0.10

1N5819-TPCT-ND    DIODE SCHOTTKY 40V 1A DO41    0.39

LEDs: try looking for some at Surplusgizmos.com like Part Number LBT30W2C-CUA-C   3mm LED 20ma Bright White 15,000 MCD  0.30     or at Allelectronics.com like CAT# LED-83  3mm diameter T-1 LED. Ultrabright white   0.95

I usually buy white LEDs and then color them with Clear Tamiya paint to suit the situation.Learn more about using LEDs here: http://model-railroad-hobbyist.com/magazine/mrh-2012-02-feb/points_of_light

The boards I use can be found here:  http://tinyurl.com/lkhpkmd     They're cheap, double sided with plated through holes.

Dave, there are lots of sources for these kinds of parts, most similar ones will work. Don't use lower Voltage Caps than 25V. Most any Schottky diodes will work that can handle at least 400 ma. You can probably lower these costs even more by hunting through electronic surplus providers on line and on ebay.

'Hope this helps. Best regards,

Geoff Bunza

Hi John!

Thanks for educating us! Sounds like it should work fine as an output device. I think I'll have to look into this more myself.

Best regards,

Geoff

What I am thinking is could someone take the project as you have put it together now and extend it to be a fully fledged decoder for use in a loco (control the loco speed, direction, lights, etc)... I have doubts that even with just the Arduino board though it wouldn't fit in any N scale locos though.

Now, for the general all scales support.... If you added some storage medium and added a an additional library or two you could in theory drive a speaker from this decoder for background sounds or perhaps factory sounds... maybe even sounds driven by random logic via JMRI (think birds making noise or cars honking etc)..

Hi,

and extend it to be a fully fledged decoder for use in a loco (control the loco speed, direction, lights, etc)

Well... yes, you're describing what a commercial decoder really is! N-scale decoders are designed with reduced size in mind, with more components specifically selected for size and performance-- that's the design criteria vendors need to meet. And it can be tough, especially when modelers don't want to pay a premium for a tiny decoder. When you throw away these criteria (and a whole lot more, like I did) you can use components that drop costs. What you see in this project are the basic, comparable guts to a decoder you can purchase off the shelf and neatly packaged. You might be surprised to learn that the Pro Mini 328P processor is actually far more capable than some internal processors extant in commercial decoders.

If you added some storage medium and added a an additional library or two you could in theory drive a speaker from this decoder for background sounds or perhaps factory sounds...

You are quite right. You might what to look here:

That  is really what I needed to get moving forward ... going to try and source all of this stuff... sort of excited about this (might be a good project for "rainy days"?).

I really like the idea of the "DCC Function Tester"; a very useful tool and simple project to get started with.  I'll then try and work up a "DCC controlled building" -- starting with loading bay doors that can open and close ... with sound!?  And that gate on the fence ... and the rail crane ... yeah, you get the idea!  :)

For the Professor -- could one of these project DCC decoders be used to trigger sounds from the Pricom Dream Player (seems that the Dream Player has been designed with that in mind)?  Wondering "how" it would/could be done?

Thanks again for this post ... pretty exciting news for me!  :)

Dave,

could one of these project DCC decoders be used to trigger sounds from the Pricom Dream Player

I have used the Pro Mini to trigger Pricom Dreamplayers. To quote from the Pricom manual"

The trigger input terminals (Trigger-1 to Trigger-4) provide connection to the low-side (Cathode) of the LED in each opto-isolator. Current limiting resistors are built-in, so you can simply connect any Trigger Input to GND to cause the Trigger to occur.

Terminal #6 (POS) is connected to the high-side (Anode) of all 4 opto-isolators. Typically Terminal #6 is connected to the power source to be used to trigger the inputs. This can be an external power source or Terminal #7 (5V), if you do not need to isolate the Dream Player ground. The internal current limit resistors are suitable for voltages from 5VDC up to 24VDC. If higher voltages are required please contact us to determine suitable added current limit resistors.

The dreamplayer is relatively easy to interface to, with no additional hardware-- a very high quality gadget!

Best regards,

Geoff

Geoff - many thanks for publishing this information.  I have been exploring do-it-yourself DCC for many years and this circuit is a welcome addition to my tool kit!

I cobbled together a unit yesterday using parts that I have on hand and have it working to an extent but not as you describe.  Perhaps you can lend a hand.

If I change the "0" at the end of this line:

 // Setup which External Interrupt, the Pin it's associated with that we're using and enable the Pull-Up
  Dcc.pin(0, 2, 0);

to a "1" so that it reads

 // Setup which External Interrupt, the Pin it's associated with that we're using and enable the Pull-Up
  Dcc.pin(0, 2, 1);

I get serial data to my serial terminal that shows:

processMultiFunctionMessage: 17,17,3F,80,AE,11

the data string is described in the file named NmraDcc.cpp indicates that it is getting info for address 17

 Serial.print("processMultiFunctionMessage: ") ;
  Serial.print(Addr,DEC) ;
  Serial.print(',');
  Serial.print(readCV(1),DEC) ;
  Serial.print(',');
  Serial.print(Cmd,HEX) ;
  Serial.print(',');
  Serial.print(Data1, HEX) ;
  Serial.print(',');
  Serial.print(Data2, HEX) ;
  Serial.print(',');
  Serial.println(getMyAddr(), HEX) ;

Receiving this data stream tells me that my circuit and my Arduino are OK but the LEDs don't toggle when I change function keys using "17" as the DCC address - The LEDs do toggle during the initialization tests.

Do you have any suggestions?

Again, this has the potential to add a great bit of utility to our club's modular layout and I thank you for bringing it to my attention!

Thanks!

dave ( http://www.trainelectronics.com  )