<html><body><span style="font-family:Verdana; color:#000000; font-size:10pt;"><div>Jon,<br></div><div><br></div><div>I use the ALIX boards for a renewable energy monitoring product and I can tell you that the AC power consumed by a well-loaded ALIX board is remarkably low -- I'm using "revenue grade" kilowatt-hour meters in the product I sell and what you saw with DC power, about 3 watts, is about what the kilowatt-hour meters I use see in AC power.</div><div><br></div><div>As regards power measurements on the cheap -- I think this is where something like an Arduino would come in very handy. So long as ground (B-) is kept common, fabricating something that could measure 6 or 8 DC power channels should be very simple. To do that, I'd make a voltage divider for the input voltage, using a 47K and 10K resistor for the divider -- 47K to B+, 10K to B-. Measure the voltage in the middle and rescale by a factor of 5.7. So, if that analog pin reports "2.54" volts (which would be 519 as the raw value -- 519 / 1023 * 5 = 2.536), you'd multiply by 5.7 and get 14.5 volts as the supply. Then use a 1 ohm resistor in the B- line to the board and measure the drop there. 45ma would be .045A * 1 Ohm = 0.045 volts, or a raw value of 9. An Arduino sketch that could do all this, and report the scaled values in real time on the serial monitor should be a very easy afternoon project, and probably very worthwhile for someone interested in developing a product they can either sell or "publish" as an e-Book or whatever.<br></div><div>--<br>Julie Haugh<br>Senior Design Engineer<br>greenHouse Computers, LLC // jfh at <a href="http://greenhousepc.com">greenhousepc.com</a> // greenHousePC on Skype</div><div><br><br></div>
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-------- Original Message --------<br>
Subject: Re: [Voyage-linux] Re: Any Hardware Voltage Monitoring/Usage<br>
Sensors Available for ALIX boards?<br>
From: Jon Meek <<a href="mailto:meekjt@gmail.com">meekjt@gmail.com</a>><br>
Date: Mon, January 23, 2012 7:21 pm<br>
To: linux123 <<a href="mailto:24bits@comcast.net">24bits@comcast.net</a>><br>
Cc: <a href="mailto:voyage-linux@voyage.hk">voyage-linux@voyage.hk</a><br>
<br>
I believe that PC Engines recommends 18 volt power for ALIX boards<br>
(other than the alix1d which requires 12 v). In any case, PC Engines<br>
sells only 12v and 18v power supplies if you buy from them<br>
directly. The 18 v PS from PC Engines is rated at 1.2 A DC but from<br>
the measurements below much less power is needed, and the switching<br>
power supply will waste little.<br>
<br>
Here are some measurements for DC and AC (120 volt) power consumption<br>
by an alix2d3 with various power sources:<br>
<br>
Switching "Wall Wart" Power Supply<br>
<br>
14.85 v 0.210 A 3.1 W DC<br>
<br>
Add HRT MusicStreamer II USB DAC:<br>
<br>
14.82 v 0.29 A 4.3 W 45 mA 5.4 W AC<br>
18.11 v 0.24 A 4.3 W 48 mA 5.8 W AC<br>
<br>
<br>
Linear Lab Supply<br>
<br>
10.97 v 0.39 A 4.3 W 0.29 A 34.8 W AC<br>
12.03 v 0.36 A 4.3 W 0.29 A 34.8 W AC<br>
13.00 v 0.33 A 4.3 W 0.29 A 34.8 W AC<br>
14.00 v 0.31 A 4.3 W 0.31 A 37.2 W AC<br>
15.00 v 0.29 A 4.3 W 0.33 A 37.2 W AC<br>
<br>
Linear Lab Supply with No Load: 0.15 A 18 W<br>
<br>
So, the switching power supplies are much more efficient as<br>
expected. There may be a question of noise from a switching power<br>
supply, but I assume that the optical isolation in the Ayre DAC will<br>
handle it. Of course you have a computer here with its own switching<br>
noise.<br>
<br>
I probably have more switching wall wart voltage choices, but the<br>
results will probably not vary much.<br>
<br>
Be careful with limiting the current to your alix board, it is going<br>
to have the need for higher power at times, just like your audio<br>
amplifier!<br>
<br>
Jon<br>
<br>
<br>
<br>
On Mon, Jan 23, 2012 at 7:33 PM, linux123 <<a href="mailto:24bits@comcast.net">24bits@comcast.net</a>> wrote:<br>
><br>
> I wanted to thank everyone who responded with this information. It’s a shame<br>
> that there are no software based sensors but I guess at the end of the day<br>
> it would only add additional overhead.<br>
><br>
> It’s interesting to hear that there would be a 5v regulator of some sort<br>
> just after the DC Input jack. If that's the case then I can see no reason<br>
> why the manual for the board tells you to use between 7-20v MAX. I chose the<br>
> 15.5v value only because it matched the Wall Wart that came with the board<br>
> and planned on working backwards from there in terms of Input power once I<br>
> felt I had sufficient information to pull the trigger....err, I mean, twist<br>
> the knob lower<br>
><br>
> One thing I will mention is that I did have the board dialed down to the<br>
> 12.5v range for a few hours one evening during a jam session and swore the<br>
> soundstage seemed a bit more distant than usual but it may have been the<br>
> beer talking to me. I will need to do further testing before I am willing to<br>
> say much more about that occurrence.<br>
><br>
> To "Jeff Mai",<br>
><br>
> I would love to be able to feed the board between 9-10v but before I try it<br>
> out I am going to place a call into Ayre to find out how much juice the DAC<br>
> is looking for to run its circuitry. If the DAC is looking for 5v, then I<br>
> may need to stay around the 13.5-14v range for Input power in order to keep<br>
> everything happy.<br>
><br>
> Thanks again<br>
><br>
><br>
><br>
><br>
> --<br>
> View this message in context: <a href="http://voyage-linux.34677.n3.nabble.com/Any-Hardware-Voltage-Monitoring-Usage-Sensors-Available-for-ALIX-boards-tp3680043p3683456.html">http://voyage-linux.34677.n3.nabble.com/Any-Hardware-Voltage-Monitoring-Usage-Sensors-Available-for-ALIX-boards-tp3680043p3683456.html</a><br>
> Sent from the Voyage Linux mailing list archive at <a href="http://Nabble.com">Nabble.com</a>.<br>
><br>
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