Current draw of Squeezebox 2 while using digital out?

[G]

Hi all. I read this forum with great interest even though most of it is over my head and I have a question. I use my squeezebox with my dac. I don't use the analog outs. I would like to build a battery supply for my SB using a battery tender JR. for the charging duties. I want to use a current switch that will turn the charger off when I power up my SB to listen to it. I was wondering if anyone had a idea of how much current that a SB2 draws when being used with only the digital out? Do you guys think this idea is doable? Thanks.

[Kevin Wood]

Well, I have a rather sick squeezebox 1 on the bench at the moment and IIRC it was taking around 0.75 amps @ 5v. I will have to try my SB3 and see how that compares, as the SB3 is similar to the SB2 internally.

Beware that the 5 volt supply needs to be a regulated 5 volts as it's used to directly power some of the internal logic. I guess you might get away with 4 Ni-Cd or Ni-Mh cells in series but otherwise I'd regulate it, especially if the charger is going to be connected with the squeezebox in place.

In addition, I believe there are some switching regulators internally in the SB2 to generate higher voltage rails for the analogue output sections. You might be better off isolating the analogue supplies and feeding them from something cleaner. If you're using the digital outs you might be able to disable that part completely, although I doubt it would have much impact on the digital stages of the SB.

Kevin

[G]

Originally posted by Kevin Wood
Well, I have a rather sick squeezebox 1 on the bench at the moment and IIRC it was taking around 0.75 amps @ 5v. I will have to try my SB3 and see how that compares, as the SB3 is similar to the SB2 internally.

Beware that the 5 volt supply needs to be a regulated 5 volts as it's used to directly power some of the internal logic. I guess you might get away with 4 Ni-Cd or Ni-Mh cells in series but otherwise I'd regulate it, especially if the charger is going to be connected with the squeezebox in place.

In addition, I believe there are some switching regulators internally in the SB2 to generate higher voltage rails for the analogue output sections. You might be better off isolating the analogue supplies and feeding them from something cleaner. If you're using the digital outs you might be able to disable that part completely, although I doubt it would have much impact on the digital stages of the SB.

Kevin

Thanks for the reply Kevin. I had planned on using this to regulate the 12v down to 5v. I will just leave out the diodes and attach the 12v directly to the regulator.

http://glass-ware.stores.yahoo.net/hps1.html

Do you know if they make a current switch that is sensitive enough for the application I described?

[Kevin Wood]

Well, I made some measurements on my Squeezebox 3 tonight. It takes just over 1000 mA when playing FLAC over wireless LAN. Unfortunately, it takes about 820mA when "off" with the display brightness turned right down, I suspect because the CPU and heaters in the display are still powered. It might be possible to detect this with a current switch but it will need careful adjustment and I suspect if you have any screen savers active when idle (e.g. news ticker) it won't work reliably since this will push the idle current draw up very close to the level when playing.

That regulator looks fine, BTW.

Kevin

[G]

Originally posted by Kevin Wood
Well, I made some measurements on my Squeezebox 3 tonight. It takes just over 1000 mA when playing FLAC over wireless LAN. Unfortunately, it takes about 820mA when "off" with the display brightness turned right down, I suspect because the CPU and heaters in the display are still powered. It might be possible to detect this with a current switch but it will need careful adjustment and I suspect if you have any screen savers active when idle (e.g. news ticker) it won't work reliably since this will push the idle current draw up very close to the level when playing.

That regulator looks fine, BTW.

Kevin

Sounds like a DPST switch is what I will be using. Thank you Kevin.