JohnActon posted:John, thanks, neat circuit just ordered the opto couplers I think I will try using my cheap eBay Chinese DC-DC regulators. They seem to be OK. You know I have had an idea running around the back of my head of burning mp3 files on micro sd boards. I chased steam excursions out of Birmingham for years and took a lot of svhs video with some really good audio. I have sounds from N&W 611 and 1218, Sou. 4501, S&A 750 pacific, Nickle Plate 2716 Berk. The CP Royal Hudson, T&P 610 and a few more. My big problem is my old svhs camera bit the dust years ago and my last svhs vcr occasionally eats tapes. Have not pulled the cover to check out the problem. Also have many still images shot on medium format film.
Any 5VDC power supply does the trick. The "magic" is really the MP3 player board, it does all the heavy lifting. I looked at doing an MP3 decoder, but for the prices of these modules, I'll let someone else do the hard stuff. 
JohnActon posted:I plan to make/play with your circuit but I think I need to order at least one ERR sound converter and see if they play well with the L2RU boards. I think I could let the coupler pulse start a timer and get some whistle function but might as well spend the money on the sound converter. Thanks again, John
The sound converter is a handy board, and you can hack the code as it's been released under the GPL and is posted in the, TMCC/LEGACY REFERENCE MATERIALS & MANUALS thread along with the schematic of the Sound Converter. I recently did a little hack to that code make the ditch lights work properly so you can use the board for diesel ditch lights that actually operate with a command horn.
