Hi all this is my setup -
Pi 3B+
IQ audio Digi-amp+
Latest volumio installed
Safe shutdown using pushbutton and led lamp ( also startup on same button)
The whole thing has been working perfectly for 2 years. I recently moved house to a rural location and find that we get frequent but very brief - a couple of seconds - of power outage. Each time it happens My SD card becomes corrupt and I have to re-write it.
I know that a fair bit has been discussed on this forum about UPS devices etc, but as far as I can tell, this has been all about backup for the 5.5volt power input for the Pi. Because my Pi is fed via the 18volt Digiamp + I need to find a way of getting up to around 5 seconds of backup supply at 18.5 volts and then a way of auto shutting down safely. I already have push button startup and safe shutdown installed. Could something be done utilising this somehow?
I really do not want to go to the expense of purchasing a mains voltage UPS as these are very expensive and it really is only my music player that I want to protect.
Any ideas.
Depending on how much effort you want to put in, you could either
– run things of a power bank capable of USB PD and request 20v from it (you should check what is the maximum voltage level supported by your Digi-amp+, but I reckon it should work at 20v)
– Pick up one of those cheap 12v UPSs for router/IP Cameras and use a boost convert to get the required voltage for your amp. This probably isn’t going to be very “audiophile” but that again also depends on what boost converter you use
Hi and thanks for the reply. "12 to 19 volts is ok for the Digi-Amp plus, but I don’t want to run it from a backup supply. I simply want to be able to enable a safe shutdown automaticaly if the mains power fails. Any ideas on that.
Unless your into electronics, doubt there’s a cheap and nasty solution as you need to monitor the mains power and send a shutdown signal to your existing Off Button on mains failure
if you know the current your amp is drawing normally, and how long it takes to shut down the RasPi it may be possible to stack a number of electrolytic caps together, have a CT (Current Transformer) on one of the mains cable cores and another SBC that will sort the logic out, obviously you will need to add the SBC’s power consumption to your capacitors.
Alternatively, get a small 12 volt battery hooked up to a car battery trickle charger (not sure how much mains noise this will add to the system) and run your Digi-Amp from that
Your audio hat that consumes 19v is still going to step down and deliver 5v to the Pi via the GPIO pins, so something like this in the middle might do what you need.
Hi and thanks for your replies.
What you suggest could possibly be a solution. I would have to look carefully at how the Hat supplies the 5 volts to the Pi and maybe isolate it so that the 18 volts supplies the hat indepenently of the supply to the Pi which would be via the type of unit you are suggesting. I’m sure it can be done. It may be as simple as chopping of the pins on the Pi that get the 5 volts. I think that there are other similar hats on the market that do the same job as well. I will do a bit of research.
Hi and thanks.
That one could work but I would still have to make sure that there is no 5 volt feed (via a 5v pin) down from the Digi-amp+ to the pi. This is how it works at the moment. I think, as in my previous reply, I could disconnect this by simple chopping the 5 volt pin so that my 18 volt supply only feeds the Digi-amp. I would then feed the Pi with 5 volts in the normal way with a separate supply. I,ll take a look.
I could do that and that would save having to use another power supply. You are right. well spotted. I would still have to isolate the Digi-amp’s 5 volts from the Pi.- ie by chopping the 5 volt pin between the two boards.
Is this in a case? as you could used a 40 way extension cable between the HAT & Pi, then you’d only have to cut a couple of leads rather than modifying either piece of hardware
Hi.
Yes I had considered that option but not sure if I have the room. The music player enclosure that I built was sized to take the components I am using and there is only just about room for a stack. I’ll open it up and take another look. Thanks.
If that was the case, how do persistent queues work and playlists? they must both write to the SD card each time a track advances or a track is added/deleted
Just very low probability a SD card write occurs (so few of them) at the same instant of time a power loss happens and the cards are more rugged now was what I thought I read.
Thanks for all of the input everyone.
This is what I have decided to do. As the risk of corruption seems to be minimal I am going to run with it. It seems too much hassle to try to run some sort of power outage protection with my setup. My SD card holder is mounted on the back of the enclosure that I built and it is a few seconds job to change the card. I keep an up to date copy on a spare SD card always and so if corruption did occur I could easily swap for the spare and re-write the corrupted one.
