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--- content:meshextender:prototyping_on_mk808 [23/04/2013 22:12]
Paul Gardner-Stephen [Comparing Power Consumption of the various devices]
+++ content:meshextender:prototyping_on_mk808 [14/05/2013 23:18] (current)
@@ Line 12: / Line 12: @@
 We are considering a few options for this, which are described below.
+Most of these are centred around the low-cost low-power Android stick-PCs manufactured by Tronsmart (http://www.tronsmart.com).
 ===== Comparing Power Consumption of the various devices =====
+==== Summary ====
+An MK808B will use about the same amount of power as the TP-LINK WR703N platform we are currently using, but with much, much better performance.  This assumes that servald will consume less than 0.3W when running on an MK808B.
+Total power budget will be between 1.0W and 1.3W, plus the power to run servald.
+An aggregate average consumption of 1.3W is probably reasonable.
+Assuming an 80% efficient power supply, and 24 hours of endurance, this indicates that we will need a 40Wh battery.
+To allow for charging a typical phone, we should allow another 10Wh, for a total of 50Wh for a system that can endure and support a smart-phone for 24 hours.
+We need to test the assumption about servald energy consumtion to have confidence in these figures.
+What is pleasing is that the MK808B does NOT use the 1.1W - 2.2W when idle that some sources on the internet have claimed.
+=== Processing platform ===
+The TP-LINK WR703N + Wi-Fi AP+ad-hoc + USB hub + USB memory stick uses about 1W to run servald, minus USB serial adapter and RFD900 radio.
+The MK808B, not running servald, and Wi-Fi in AP mode only (we don't know how to do simultaneous ad-hoc + AP uses on it) uses about 0.75W, less than the WR703N.  But servald running will presumably push that up somewhat.
+The MK802ii uses about 1W to do the same job as the MK808B, which is more than the MK808B uses.  So the MK802ii is out on the basis of inferior power consumption and performance compared with the MK808B.
+The MK808B, apart from the lack of simultaneous AP+ad-hoc Wi-Fi looks like the clear winner at this stage, provided that servald doesn't consume lots of power.
+=== USB/Serial adapters ===
+The CP210x adapter uses about 0.14W, while the FTDI adapter cable uses about 0.12W. However, the cable is too large for the slight power saving that is offers.
+=== RFD900 Radio idle consumption ===
+The RFD900 adds between about 0.04W and 0.3W when operating at a TX power of 100mW.  Average consumption could not be easily measured with the bench supply that these tests were performed with.
+==== Raw Measurements ====
   * MK808B (idle, Wi-Fi client mode, HDMI display connected and on, Serval Mesh not installed, no serial adapter plugged in): averaging 0.187A - 0.198A @ 4.995V = 0.94W - 0.99W
   * MK808B (idle, Wi-Fi client mode, HDMI display disconnected, Serval Mesh not installed, no serial adapter plugged in): averaging 0.145A - 0.155A @ 4.995V = 0.73W - 0.77W
   * MK808B (idle, Wi-Fi client mode, HDMI display disconnected, Serval Mesh not installed, CP210x serial adapter plugged in, no RFD900 attached): averaging 0.173A - 0.180A @ 4.995V = 0.87W - 0.90W
+  * MK808B (idle, Wi-Fi AP mode, HDMI display connected and on, Serval Mesh not installed, no serial adapter plugged in): averaging 0.187A - 0.201A @ 4.995V = 0.94W - 1.01W
+  * MK808B (idle, Wi-Fi AP mode, HDMI display disconnected, Serval Mesh not installed, no serial adapter plugged in): averaging 0.146A - 0.157A @ 4.995V = 0.73W - 0.79W
+  * MK808B (idle, Wi-Fi off, HDMI display connected and on, Serval Mesh not installed, no serial adapter plugged in): averaging 0.143A - 0.144A @ 4.995V = 0.71W - 0.72W
+  * MK808B (idle, Wi-Fi off, HDMI display disconnected, Serval Mesh not installed, no serial adapter plugged in): averaging 0.102A - 0.103A @ 4.995V = 0.51W - 0.52W
   * MK808B (idle, Wi-Fi client mode, HDMI display disconnected, Serval Mesh not installed, CP210x serial adapter plugged in, RFD900 attached (TX @ 100mW), but no link): averaging 0.209A - 0.26A(but jumping between 0.21A - 0.26A wildly, presumably based on whether it is TXing) @ 4.995V = 1.04W - 1.3W
   * MK808B (idle, Wi-Fi client mode, HDMI display disconnected, Serval Mesh not installed, CP210x serial adapter plugged in, RFD900 attached (TX @ 100mW), link but no traffic): averaging 0.22A - 0.27A(but jumping between 0.22A - 0.27A wildly, presumably based on whether it is TXing) @ 4.995V = 1.05W - 1.35W
@@ Line 22: / Line 61: @@
   * MK808B (idle, Wi-Fi client mode, HDMI display disconnected, Serval Mesh not installed, FTDI serial adapter plugged in, RFD900 attached (TX @ 100mW), link but no traffic): averaging 0.210A - 0.25A (but jumping around wildly in that range) @ 4.995V = 1.05W - 1.25W
   * FTDI cable + RFD900 (TX @ 100mW) with link but no traffic: 0.048A - 0.09A @ 4.995V = 0.24W - 0.45W
+  * FTDI cable + RFD900 (TX @ 250mW) with link but no traffic: 0.037A - 0.12A @ 4.995V = 0.19W - 0.60W (but peaks are likely reduced due to sampling issues in our test environment).
   * CP210x cable + RFD900 (TX @ 100mW) with link but no traffic: 0.066A - 0.1A @ 4.995V = 0.33W - 0.50W
   * MK802ii (idle, HDMI display connected, Serval Mesh not installed): 0.21A - 0.30A @ 4.995V = 1.05W - 1.50W

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