In the description you mentioned that a higher value  will speed up the servo travel. Could you tell me what is the highest value ( quickest travel speed I can use) or what I am doing wrong

'Hope this helps. Have fun! 

So many possibilities! Thanks for sharing.

Tom

Hi Tom,

You are most welcome.

Even though there are many comments to wade through, there are even more variations reported in the comments.

Enjoy and have fun! 
Best regards,
Geoff Bunza

Hi Geoff,

would there be a reason not to use this optocoupler: CNY17? Here a NPN transistor can be switched as either open collector or as emitter-follower. It is not as fast as the 6N137 but more flexible; and I have plenty in stock.

Grts, Erik

Hi Erik,

Unfortunately, the CNY17 is likely not going to work. It looks to be more than 100 times slower than the 6n137 and is similar to a couple of opto-couplers I tried before settling on the 6N137. Like you, I had acquired a number of these slower couplers via surplus sales over the years. It might be a "learning" exercise to try a few of the CNY17's. The ones I tried either never worked at all, or generated errors under different operating conditions. There is a possibility you might be able to "select" a few that will work out of a large number, which is sometimes done in industry. I don't think this is worth it, and I would just go with the 6N137. Also, I have seen people omitting the 270pf capacitor C8. I recommend it always be included, based on my actual experimentation and results.
'Hope this helps. Have fun! 
Best regards,
Geoff Bunza

Hi Geoff,

thank you so much for your concise and detailed reply! So amazing that although we are thousands of miles apart we get almost instant replies!! Indeed I will not waste time with the CNY17.

I am planning a Eagle schematic and board using SMD: would I be able to upload the .sch, .lbr and .brd files here for others' use?

If not, I would send them to you for your use.

Grts,

Erik

Hi Erik,

I would be delighted for you to share your work. For files I want to share with others, I usually create a zip file, as it is usually smaller, and zip files are readily accepted here on the MRH site, and in many email servers. If you have trouble uploading (you can use the link icon above and upload the zip file) you can also send it via a private message (PM) and I'll make sure it is put right.

Good luck with your project. Have fun! 
Best regards,
Geoff Bunza

Hi Geoff,

for the link: do you mean the one in the commentary section, second row, third from right?

As soon as ready I will upload the zipped files.

About the examples in the NmraDCC folder from this project download, there is an example "Dec_15Serv_2LED_6Ftn" as well as "AccDec_15Servos_2LED_6Ftn" but no "Decoder_15_Servos_1_LED_4FTN" as per your description above page 1.

Did I miss something?

Grts,

Erik

Hi Erik,

for the link: do you mean the one in the commentary section, second row, third from right?

Yes, that is correct. If you hover over it with your mouse pointer "Link" should appear.

About the examples in the NmraDCC folder from this project download, there is an example "Dec_15Serv_2LED_6Ftn" as well as "AccDec_15Servos_2LED_6Ftn" but no "Decoder_15_Servos_1_LED_4FTN" as per your description above page 1.

Did I miss something?

No, you did not miss anything... I did! My apologies. The article has since been corrected to correspond to the Version 5.4 download:

There are two folders in the zip file: NmraDcc and SoftwareServo

If you have set up and installed the Arduino development code from http://arduino.cc/en/Main/Software  (Read on for details)

Then copy both folders to \My Documents\Arduino\libraries on yourcomputer. Then look for examples in NmraDcc and you will find Dec_15Serv_2LED_6Ftn,Dec_13Serv_4LED_6Ftn, Dec_10Serv_7LED_6Ftn, and Dec_17LED_1Ftn.

Respectively representing pre defined decoders with 15 Servos F0-F14 and 2 LED F15-F16, 13 Servos F0-F12 and 4 LEDs F13-F16, 10 Servos F0-F9 and 7 LEDs F10-F16, and last 17 LEDs F0-F16 like the original decoder I presented.

I very much appreciate you pointing this out. Many thanks! 
By the way, where are you located?

Have fun! 
Best regards,
Geoff

Hi Geoff, it is my pleasure.

And my location: https://tinyurl.com/r7o6bpz