Stan, I can always trust you to come up with a list of questions! I'd dismiss them out of hand, but they're almost always pretty insightful and to the point. 
@stan2004 posted:This is very exciting!
Sorry for the delay but as a card-carrying member of the Peanut Gallery:
Power:
100-200mA when audio active. But what is it in standby (no audio)? I'm thinking of battery applications.
10-18V AC. What determines the limits on the low end? Like your LED-light board, I think you can reach some conventional operators if we understand what's going on ~10V AC. For example, this may be a case where using a chopped-sine CW-80 or Z-1000 controller is preferable in conventional since it provide the high voltage peaks even at low throttle settings.The power when idle is... I'll have to go measure it.
WOW, I overstated the power requirements, next rev has to revise that part of the document. Truthfully, the power varies based on the voltage as the power source for the board is a switching power supply. At 7 VDC (lowest it'll go without the 5V switcher starting to drop out of regulation), the standby power is 25ma. Boost the power up to 18VDC, the current is 10-11 ma. I'm assuming that with AC into the full wave bridge and 680uf cap, I'd get about the same readings.
The power with a fairly loud and busy sound file at full volume and 7VDC is right around 100ma. Obviously, it jumps around a bit, but stays within 90 to 105ma. At 18VDC, it's about 42-23ma average, again jumping around a bit.
For a conventional application, what does the MP3 logic do upon loss of power? Is there any provision to, say, add more capacitance so the board doesn't “reset” on a ~2 second track power interruption for conventional direction change? I think it's OK for the audio to mute during power loss but the idea is the audio picks up where it left off without requiring a "new" trigger.
The audio drops out pretty quickly at 18V, and obviously even quicker at 7V. I didn't actually consider trying to bridge power gaps, that's a bit more challenging, not to mention would likely involve somewhat bulky components. Anything's possible, but at some point I had to stop engineering and produce something, even it it isn't a "fits-all" solution.
If you draw the 200 mA (max) from the 5V output pins, can the DCS inductor handle this much current when audio is running (itself drawing 200mA)?
The choke for DCS is a 780ma choke, and based on my measurements, it's unlikely to see much more than 100ma, so I don't see any issues there.
MP3:
How is stereo MP3 processed? Does it just combine Left and Right? Seems a few years ago when we discussed this there was some talk of making one audio track separate so that it could be used for non-audio purposes. I suppose this depends on how your MP3 module deals with Left and Right.
The module I use is the BY8001-16P MP3 Player Module, that's a link to the description. The MP3 player is a stereo device, but it only has one mono amplifier, so I simply convert any audio file to mono to use with the board. It has stereo output channels that are just low power for earphones or an external amp.
How do you name the .MP3 files on the microSD card to correlate to trigger 1...5. Alphabetical, etc.
This is a place where I spent some time attempting to make the layout of the micro-SD files clear in my latest document revision. I've updated the manual in the first post, see if that makes it clear. It is somewhat odd, but I had to live with the limitations of the MP3 module, because I was in no mood to reinvent that wheel.
Triggering:
What is the minimum trigger pulse width?
Don't know for sure, I know it triggers on around 20 ms pulses, and I suspect less. I use the same triggering as on the RF receiver I'm working on.
Does a new trigger over-ride a currently playing sound? Or does it queue up triggers always finishing the first sound before starting a new one?
Good question, there is actually some jumperable options on the MP3 player module to change the behavior. There's a jumper pad to select various options, the shipped default is 010. A second trigger on the playing track will restart the audio. With the 000 option, only selecting a different track can interrupt the audio.
If I ever get energetic, there's also a complete serial protocol to do all sorts of things with the module, but I decided that would be a longer project that I wanted to make this. I think it will fit into a lot of slots without having every possible option.
What happens for simultaneous triggers? I suspect your MP3 player cannot decode/mix multiple MP3 files?
Correct, it will play whichever one arrives last, even if it's by milliseconds. It won't play multiple
If you keep a trigger active when a sound completes does the audio repeat (loop) or do you need a new “transition” from off to on?
You need a new trigger.
Outputs:
Aside from tacking a wire into one of the 4 RF receiver outputs, is there any method to have one or more 4 RF outputs control/drive a relay or some other non-audio circuit?
No, but my soon to be available RF receiver will be glad to do that for you.
Related to above, many RF relay modules that understand 1527 protocol operate on 12V DC. Have you considered how to pair this module with a DC-powered wireless relay? Just the DCS inductor and bridge rectifier (I think I see one there) go a long way! I really believe being able to control sound AND simple ON/OFF whether lights, a motor, an electro-coupler, whatever, would make this even more universal.
Again, I have the relay based RF receiver to do this very task. Obviously, for the DIY guy, adding a couple components to power the 1527 relay module wouldn't be an issue to add this capability.Oh... and if you are looking for beta sites you know my address!
I certainly do.
